Why The Army’s Next Round HAS to Be Light – In Just One Simple Example

We are at a crossroads in small arms development. Demands for improved weapon effectiveness have reached their apex. At the same time, the soldier’s burden has grown into a crisis so pressing even the Army Chief of Staff has acknowledged it in testimony to Congress. Soon the next ammunition configuration will be decided, as new technologies open the door for a rethinking of the infantry’s most basic weapons.

Whatever round they choose, it has to be light. Here’s why, in one simple example.

Since both the load of the soldier and round effectiveness are serious concerns for the next small arms configuration, perhaps the right answer is to split the difference and go with something directly in the middle. However, “in the middle” probably doesn’t mean what you think. I’ll explain.

Let’s assume two rounds: One weighs 10 grams, while the other weighs 20. Since the first round is half the weight of the second, a soldier can carry twice as much per kilogram. Let’s go ahead and express that mathematically:

1000 g / 10 g = 100

1000 g / 20 g = 50

If we want something “in the middle”, we need a round that allows the soldier to carry more rounds than the 20 g round, but we decide it’s probably OK if he can’t carry as many as the 10 g round. 75 rounds is right in the middle of 100 and 50, and we determine that would be satisfactory. Simple intuition tells us this round needs to weigh 15 grams to give us that combat load:

1000 g / 15 g = 66.66… !!!

That’s right, splitting the difference does not give us a combat load in between the two rounds, it gives us a combat load twice as close to the 20 g round as the 10 gram round! This case illustrates that our natural intuition with numbers is wrong, that in fact the halfway point is somewhere else:

1000 g / 75 = 13.33… g

So, paradoxically, the midway point for a given combat load between the two rounds is twice as close to the lighter round as the heavier!

To drive the point home, we’ll repeat the example with the masses of two real rounds: 5.56mm NATO and 7.62mm NATO. 5.56mm weighs about 12 grams per shot; 7.62mm about 24 grams. Keeping in mind that the average of 12 and 24 is 18, let’s see how the math shakes out:

1000 g / 12 g = 83.33…

1000 g / 24 g = 41.66…

1000 g / (83.33… + 41.66…)/2 = 16 grams

It’s counter-intuitive, but it’s simple math. The next round has to be light, because the halfway point isn’t where you think it is.

(For the math geeks in the room, you have already figured out that it is the harmonic mean you need to use for this problem, not the arithmetic mean. Since this is a family-friendly site, I omitted these terms to keep things understandable for everyone.)



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Bill Wilson

    Imagine how great it would be if there was some small, light intermediate round, that is effective at realistic combat distances, was already adopted and in mass production..
    https://uploads.disquscdn.com/images/83e0b863f07970ae5885cf1b4f828fd5888ba0dd3e32b36b27538377b3c2159e.jpg

    • PK

      No kidding.

    • Dr. Longfellow Buchenrad

      Stop trying to indoctrinate us with your .50BMG agenda.

    • ostiariusalpha

      Yabbit waddubout dat bawdy ahmuh?! 😰

    • b0x3r0ck

      That round your talking about is only going to be effective at 50-150 VS next gen body armor making it a smg round at best.

      • iksnilol

        But 7.62×51 is equally crappy against armor as 5.56. They both go just fine through level 4 armor with tungsten core bullets.

        • noob

          where can I buy shares in Tungsten? We are gonna need a lot.

          • ostiariusalpha

            China has large deposits of tungsten. 🤔

          • noob

            “I was in the United States for three years when I was a captain. I was taught how to drive by some American officers, and I bought a car. I went around the States, and I knew the close connections between the military and industry. I saw the plant area of Detroit, too. By one button push, all the industries will be mobilized for military business.” – General Tadamichi Kuribayashi, IJA, b1891-d1945, the last commander of Iwo Jima.

          • iksnilol

            Especially if they go with 7.62×51.

        • b0x3r0ck

          Then the question should be asked at what distance can the .308 and 5.56 pen lvl4 armor at with tungsten core bullet. What distance would a replacement round like the 6.5 creedmore pen the same armor with a tungsten core. By the end of the day it’s getting back to normal engagement distances VS armor targets. Dealing with soft targets can be fixed with things like cnc bullets to displace flesh.

          • iksnilol

            Yes, but why move away from 5.56 then? When your engagement distances won’t change.

        • ActionPhysicalMan

          I rather hope they end up with a round that can penetrate at least one generation more advanced than current level 4 armor.
          I am not advocating it for the military, but my choice right now is a .243 WSSM AR and and a supply of impact resistant tungsten carbide rods to be ground into penetrators should the SHTF. The cartridge shape is efficient for holding powder with less material. It also doesn’t have to be loaded with the carbide and to barrel burning levels unless you think you are facing armor. For instance with a 100% load of 3100 QL says it only reaches about 45,000psi but pushes an 87gr projectile to 2950fps in 22″. With a 100% load TinStar you can push the same 87gr projectile to 2400fps but have something like a 15000 rnd accurate barrel life. It is a very versatile cartridge. Then again the low magazine capacities are not a problem for me since I doubt I would engage in much suppression fire. I also like single stack mags and nearly impossible to find brass. No need to tell me I am an idiot – I already know:-)

      • CommonSense23

        And you think 7.62 is going to do any better?

        • b0x3r0ck

          No I think alot of other rounds would be better. The army going to a 308 battle rifle is just them switching to a platform they can work with better in the future.

      • Evil13RT

        The question is how much is needed. I’d see the point if we were shooting most of our enemies at long ranges, but the majority of kills are still being raked in by airstrikes and artillery (last I understood…). So the purpose of the gun is to keep them from getting closer.

        If it penetrates at 150 yards as is then it’s able to piece armor at distances longer than we are able to connect at on average. Penetrating at longer ranges is a waste of energy that the soldiers still have to carry.

        • b0x3r0ck

          There are times when you either don’t have or can’t use a airstrike/artillery to solve the problem. But do you know what a soldier wil have on call all the time there rifle. Personally I would rather be on the winning side of an unfair fight than wondering if I can make it in a fair fight.

          • Evil13RT

            My concern is that the larger rounds do have a weight penalty. Having more of a round that is moderately effective can mean more than having less of a round that is slightly better. Yes You might be able to hit someone at 500 yards, but if you run low on ammunition they’ll end up far closer.
            Since the future could bring a more widespread use of drones and small guided weapons, a better bullet might not be necessary.

  • snmp

    steel cased ammo are lighter & cheaper than brass

    • Just Say’n

      So, Wolf 6.5 Grendel. Problem solved!
      (oh wait, it’s made in Russia….)

    • USMC03Vet

      Big Ammo would never allow that.

      • Kivaari

        Big ammo contracts to run the military’s loading equipment. They would all fall all over themselves to get the contract. It isn’t their money that would buy the loading machines and raw materials. They just contract to operate it.

    • Kivaari

      In the long run steel ammo cost just a much as brass since the loading machines wear at a faster rate. It’s a wash.

      • The important thing about steel cases is they don’t use copper. Consider it one of my eccentricities, but I am in favor of a steel cased option for next generation ammunition (provided – or perhaps hedging against – composite does not work out)

        • Kivaari

          I agree. Copper is a strategic metal. Our domestic sources are fewer and fewer. We have the mineral wealth, just an inability to extract and refine the product.

      • snmp

        Many loading machines are build/made with softer parts for brass not steel. Bras is nice for civilian, but in industrial warfare steel case are better cause of weigh in logistic point view and cheap raw material.

  • A.WChuck

    Thanks Nathaniel for the reality check.

  • 5.56

    Nathaniel do you know the velocity of 5.56CT? It says “3022fps at 78yards” , but that, even with a really well shaped M855A1 replication needs roughly 3248fps at the muzzle?
    Kinda strange.

    • ostiariusalpha

      Kori Phillips said to Nate that the combustion geometry of the polymer case was particularly efficient. I’d like to see what test equipment they used to get that velocity though.

      • 5.56

        The question is if that number is right or just totally off. They make a lot of math and technical errors in the presentations…

      • They are basically stuffing propellant into the case at over 100% loading density because of the cap. So the propellant is burning more uniformly and with higher thermodynamic efficiency.

    • Where are you seeing this? Something sounds garbled to me. 78 feet, not yards, is the usual test standard. If that’s the discrepancy, than 5.56mm CT is right around M855A1 performance.

      • 5.56

        Oh gosh, big mistake from my side… yard, meter, feet, inch, moa, grain, gramm, kilo, pound, ounce – all day long, make you oversee that sometimes.

        • 5.56

          = ~3100fps , nice to finally know!

          • 5.56

            *even tough i wonder what exact barrel lenght…

  • Johannes von’ Strauch

    Verry well written article! People dont count such things in mostly, and present stupid and half hearted “solutions” with a ton of cherry picking…

  • Tim

    I see in the Army’s future 7.62 NATO and a robo-mule (or 3)for every squad.

  • MSG1000

    First, I think it’s worth mentioning a past entry on this site titled “How Much Does Your Ammo Weigh?”.

    I’d post a link but I don’t want my post to go into moderation. Anyways, one thing to note from it is that 9mm NATO weighs a bit more than the 5.56 at 12.6 grams versus 12 grams. Since 9mm brass weighs less and holds less powder the difference must come from the bullet weight.

    Ergo it won’t take much of a change in caliber to make Nathaniel’s point.

    Secondly, using his example but 5.56 (12 grams) and 7.62 NATO (23.7 grams): 210 5.56 rounds is 2,520 grams. Dividing that by 23.7 nets you 106 7.62 rounds.

    The difference between 210 and 106 would be 158. So 2,520 grams divided by 158 rounds would be an individual round weight of 15.95 grams. So 16 grams would be the limit for an in-between round count.

    All the heavier than 5.56 calibers he listed are significantly above 16 grams, potential ballistic effectiveness aside can anyone even think of a common rifle cartridge that is around 16 grams?

    • 5.56

      And increased weapon weight (barrel, bolt, bolt carrier, etc. And diffrent amount of magazines will further change all of that.

      210 rounds in 7 30round mags, are more weight efficient, than less rounds in lower capacity (and heavier) mags.

    • Jason Culligan

      According to released figures, 6.5mm CT ammo comes in at 15.35 grams. That can’t be a coincidence.

      • nova3930

        That’s part of the reason I think the new “7.62 rifle” will eventually end up as a 6.5mm CT rifle. It’s just a way to ditch the AR platform and it’s limitations early….

        • ARCNA442

          Except you’re not going to make any COTS 7.62 rifle fire CT rounds. If they really want CT then they need to actually fund and prioritize that program.

      • 5.56

        It still increases the load…. Because it needs 8 mags for 160 rounds = 3,535kg. Instead of 210 rounds of 5.56×45 in 7mags = 3,492kg

        + increased weapon weight, strong recoil increase (slower follow up shots), mag capacity reduced by 33,33%, etc.

        • Jason Culligan

          Absolutely, any increase in calibre is going to result in an increase in overall weight. I’m in no way an advocate for dropping the 556.

          That being said, if you’re going to select something that is a larger calibre then 6.5mm CT makes sense. Benefit of increased punching power with a weight that’s still close to the optimal middle ground.

          • 5.56

            6.5 CT is an unoptimised joke

    • iksnilol

      steel case 7.62×39?

      • Above the midpoint.

        BTW, the midpoint is not the idea weight. It’s just the midpoint. My recommendation is round mass no higher than 110% that of M855.

        • MSG1000

          I figured as such but I thought it was worth doing the comparison anyway.

    • Yep, this is something folks need to be aware of moving forward. I’ve seen a lot of arguments to the effect that “well, CT/composite cased 6.5mm is 15.5 grams or so, so it’s almost as light as 5.56mm!” No, it’s not (especially since mags hold less). Here’s what we’re looking at per kilo (polymer mags included):

      5.56mm: 60 rounds

      7.62mm: 31 rounds

      6.5mm CT: 44 rounds

      So, actually, 6.5mm CT is still closer to 7.62mm in terms of rounds carried than 5.56mm. This sort of thing has to be accounted for.

      BTW, I wrote that article. It’s based on my ammunition collection. It’s hyperlinked in the article you’re commenting on:

      http://i.imgur.com/1lrlH7d.png

      For the lazy who don’t want to scroll up.

      • MSG1000

        Sorry didn’t notice the hyperlink!

  • Hrachya H

    Very interesting! Let’s see how that works with the bullet weights …just curious. So the arithmetical mean of 55 grain M193 and 147 grain M80 bullets of 5.56x45mm and 7.62x51mm NATO cartridges will be: (55+147)/2=101 grain. The harmonic mean of the same bullets will be 2/(1/55+1/147)=80 grains !

    • Weird, ~80 grains keeps coming up as the max acceptable projectile weight for an infantry rifle round in my studies. Hmmm…

      • Johannes von’ Strauch

        I use 73 up to 88 grain as development area in the class IELR (ofcourse differing velocity). And in the class MEMR its 76 up to 92 grain.

        Spending years on this, youre correct, its the best area for projectiles.
        The key ofcourse is to use the right cases (light advanced bottleneck types) or for newer weapons Cased-Telescoped / advanced-Cased-Telescoped.
        Also to minimize charge weight for the wanted velocity (less recoil). And perfect its aerodynamic.

        This weight area is also substantial more Energy to Recoil efficient than the 100+ grain area. And for a given muzzle energy has more hit propability.

      • Evaris

        Well, just as a hypothetical, how would a 6.5 Grendel equivalent, firing a ~100 grain round of similar construction to M855, and utilizing cases of the same construction as Shellshock’s NAS3 fair in terms of weight?

        The main reason I ask is that Grendel’s SAAMI spec fits within Shellshock’s claimed pressure capacity last I checked, so it’s a point of curiosity of mine.

        • Lightweight cases do reduce ammunition weight, but they are not a panacea. Shellshock claims a case weight reduction of 50%, but that is for 9mm. I have not modeled a Shellshock case, but it would probably not be much if any better than a composite polymer case. So we’d probably be looking at over 15 grams. Below the midpoint, but still considerably heavier than 5.56mm.

          The Grendel is also a bit backwards as a design. Its terminal characteristics are well optimized for a range band that its ballistics and the platforms it would be used in aren’t terribly well suited for. It might hit fairly hard at 800 meters, but its trajectory would make it trickier to make those hits in the first place, and it’s not at all clear to me that a round designed to be used by a 19 year old kid who probably has bad vision or glasses should be designed around that range band.

          The Grendel is also unlikely to be very effective versus armor, due to its low weight.

          Lightweight cases do open up the possibilities somewhat, but they are not an excuse to throw care to the wind, in my opinion. And, ideally, they would be used to reduce the load, not keep it the same while facilitating something much more powerful. That’s my opinion.

          • Evaris

            Assuming the military regardless of any sense is in the market for a 6.5mm round, and you were to propose a more conventional on-the-market round, just loaded into a shellshock case, what would you be going for?

            The main reason I ask about Grendel specifically in this situation above is regarding the “designed to be used by a 19 year old kid” bit with it’s recoil impulse compared to what the army seems to be looking at last I heard, combined with the Shellshock option to bring down weight within it’s pressure limit of 60k. 6.5 Creed and the like push above that, which really rule them out, and cased-telescoped rounds so far appear to increase complexity and weight of the platform they’re used in, at least of what pictures and articles have been made available of them.

            So I came back to Grendel in my head if the military is dead-set on 6.5 like they appear to be, but… I don’t know everything that’s out there.

          • I would recommend the lightest round that would meet a comprehensive set of requirements. Those requirements would ideally be based on extensive soldier and unit studies which would help determine how effectiveness is characterized and how to best utilize the soldier’s limited payload through the lens of how those units are expected to fight.

            I suspect a resulting round would be somewhere between a little smaller than and a little bigger than 5.56mm, but with a more efficient projectile design and shape, and possibly a lightweight case.

            We are not going to get this, not soon. What we will get instead is a move towards 7.62mm, and maybe a caliber change towards 6.5mm (Creedmoor or .260) after that. Once all the dust has settled from that decision and the disadvantages become obvious, I think maybe some of the ideas I am talking about here will finally be incorporated into small arms ammunition planning.

            I think for most soldier applications the 6.5 Grendel is not well optimized, although it is a well-designed round given what its creators were going for.

  • Brett baker

    So, how about some love for the 6.35×45? (.25-45 Sharps) Probably not much better than 5.56, but it is deer- legal. Not that means anything to people who understand ballistics.

    • There is no love for the .25-45 Sharps. There was rumored to be love for it once, but science has not confirmed it ever existed.

  • Then you need to arithmetically mean the LENGTH of the cartridge between 45mm and 51mm.

    • ostiariusalpha

      Those are the case lengths, not cartridge lengths.

      • close enough for government work and everyone with an iq over 50 will infer the meaning.

        • ostiariusalpha

          Anyone with an IQ over 80 would have written it correctly to start with.

          • Or been busy enough with real paid work that it made no difference to them

          • ostiariusalpha

            It’s lunchtime here, I have time for you.

  • M-dasher

    Rarher that sqaubble about light weight ammo……why dont we just do the sensible thing, and give our boys AR10s in .308, and then actually spend the money to develope light weight body armor

    • Aaron

      Exactly how is that “sensible?” Other than “muh feelings herr durr 7.62×51 stahpping powuh!” Reducing the weight of constant load items I can agree with but not so you can bump up to an inefficient round like 7.62×51.

      Looking at the armor the question starts to become protection vs mobility. Does the level IV armor on the chest and back offer extensive improvements over a lighter weight UHMWPE level three? Does the size of Level III UHMWPE critically effect mobility and manueverability?

      On the carbine arrange the weight of the barrel back to the chamber while keeping the weight past the FSB lighter than SOCOM yet heavier than pencil reduce the weight of the upper and lower receivers through modern LiAlu forgings that are ounce for ounces “stronger than” 7075-T6 Aluminum. Look to the commercial market to see if there is any furniture for the carbine to reduce the weight while not dropping the strength by a dramatic factor. Look for trends on how the unit mounts force multiplying equipment like their IR LASERs and any other piece needed to fulfill their role. Take the info back to Knights and DD and see about shaving the unnecessary rail stretches down to reduced sizes. They don’t necessarily have to go to negative space mounting. Go to battery manufacturing and see where you can reduce weight of the batteries while not reducing their useful charge length.

    • iksnilol

      But that isn’t the sensible thing to do.

  • Fast Forward

    Nathaniel,
    From an engineering and operational reliability perspective which of the cartridges shown (excluding 5.56) has the most optimum physical case characteristics, regarding loading and extraction into a semi, or full auto rifle/carbine/MG?
    Are .260 Remington, .264usa or 6.5x47L, to name but a few, any better than the ones shown above?

    • Physic

      All of them utterly underperform and arent worth a damn to further develop. Far better is possible.

      • Fast Forward

        Could you elaborate regarding; ‘under perform?’
        In terms of what we have, here and now, could you list them as; best to worst?’

        • Physic

          6.8’s shape is absolutly hilarious, its also slow and fat (low steel penetration), it has bad weight, insanly stupid trajectory, bad supersonic range, uneeded recoil.

          7.62×39 has worse ballistics, but atleast was an answer to a question at its time. And now good for 3rd world militas.

          6.5 has ok ballistics, but far from perfect, it also is stupidly slow and heavy, has unneded recoil, and is simply unacceptable for military use due to its extrem shallow case angle that results in a ton of stuck cases and problems in automatic weapons… Also due to its large casehead (area for the pressure to act on) it has dangerous high bolt lug wear.

          .280 british has a good case angle and dont need an exessive powder charge, but .28 inch is just absolute senceless as diameter, it makes it stupidly slow, which has extrem negative effect on trajectory, winddrift, supersonic range, steel penetration. Also its large projectile makes it weight and recoil worse for no good reason.

          6.5 creedmore has good velocity for a better trajectory winddrift, supersonic range. But totally sucks at recoil, weight, capacity, and still has insanly unperfected aerodynamics, where it wastes a ton of performance. Its case angles also are dangourously shallow… And it has low barrel life.

          .264usa is more of a mix. But beeing slower again makes its trajectory, winddrift, supersonic range worse. It too has totally unneeded recoil and weight.

          Far better, in every area is possible.

          • iksnilol

            Form Factor?

        • ostiariusalpha

          He means unconventional case and projectile designs. Which is pretty obvious, since there’s always room for improved technology. But among conventional, bottlenecked cartridges, there’s a good case to be made for several caliber sizes: 6mm bullets have even better ballistic coefficients than 6.5mm, and they’re softer shooting; bullets with calibers under 5.5mm haven’t been explored much lately either, despite their potential. There are also alternative ogive profiles that haven’t seen much exploration; between the Von Karman and secant ogives, there’s an entire world of possibilities.

          • Physic

            Who spoke about “unconventional”…? Its not CT, its not CL. Its extremly close to normal bottle necked and work in those weapons.

  • Stuki Moi

    This consideration, the need to penetrate armor, and improved sighting systems putting increased emphasis on combat effectiveness at longer range, combine to recommend a small caliber, fast moving round for the next military rifle. One where possibly decreased lethality round for round, is made up for by a platform that facilitates multiple hits on target.

    In all honesty, given that high velocity and simultaneously high SD is indicated for both armor performance and longer distance work, it also points to a cartridge that is overbore by current standards. Hence benefits from the longer barrels made possible by a bullpup configuration…..

    • Funny you mention this given the round I’m currently futzing around with. 4.85mm, 3,700 ft/s muzzle velocity. Pretty decent results according to my models.

      Would give the big bullet crowd fits, though.

      • Johannes von’ Strauch

        Sounds cool, as once noted in the email, i use 3700fps as upper maximum.
        Im currectly working as a small side project on some lower SD but excellent ballistic performance projectiles (still verry good center of balance), so i got much less problems with heatflux, pressure, charge weight for such fast projectiles.

        How is your 4.85 in therms of heatflux and powder charge?

        • Should be fairly reasonable. If .260 is being considered, I’m not sure heat flux is really the issue.

          I wrote a whole article about heat flux, but it has some problems. I should revisit it sometime.

          • Johannes von’ Strauch

            Yes if .260 is tought about than 4.85 is no problem.

            I think i should integrate the light projectile i spoke about to in what i send you.

            Yes i asked in the g+ chat that i really wondered why you used the circle area of the bore not the wall area for heatflux?

          • IMO, what we really care about is probably total in-bore wasted heat per unit barrel mass. Rifling isn’t really the failure point in extreme strings of fire, the barrel’s integrity is.

          • Johannes von’ Strauch

            Yes, i more tought about gas erosion, not heat stringing. But it would actually be a really good idea to implement such a chart in the Whitepaper.
            Even tough the big caliber croud ofcourse would argue that heat stringing is similar due to that with the “stowed kills” you need less rounds anyways haha.

          • noob

            How smallbore can a select fire arm go and still be able to buck wind and carry downrange?

            Could a 55gr 3.75mm high BC projectile get there at speed, and in large quantities?

          • You’d need empirical testing to back this up, but, uh, that 4.85mm I was talking about has like 30% less drift than 7.62mm according to the charts, so… Pretty small!

          • ?

            Which 7.62×51 projectile at what velocity?

          • M80 at 2,800 ft/s.

          • ?

            And 30% at what range?

          • 1,000m.

          • noob

            whoa. so you could just have a red dot for all practical ranges and wind?

          • Depending on what you considered “all practical ranges”, sure. Out to 400m I think.

          • Johannes von’ Strauch

            Sounds a bit like a 40grain AR2 …? (1649J ME, 196J @1000m, 130J @1200m (even tough that can overestimate it due to the shape beeing highly velocity dependant and getting less efficient at range).

          • Johannes von’ Strauch

            *edit, just forgot to count in lands vs goove diameter, so the numbers at range do change.

          • Johannes von’ Strauch

            *what groove diameter do you use in inch/ and mm?

          • 37gr AR-2, yeah.

          • Johannes von’ Strauch

            Whats the wind drift in inches at 1000m, 30% can ofcourse be rounded, and in what calculator. Do you use a realistic dynamic FF (velocity related, therefore g7bc changing at range), or just simply the rather less realistic “0,835” FF of the AR2.

          • JBM uses a dynamic FF.

          • Johannes von’ Strauch

            It shows you the numbers for a given velocity… I quess you use the G7BC and FF?

            Not sure if there is an option to use this specific shape and simulate a shot at range with every single yard by yard calculated exactly over and over again dynamicly.

            I found JMB rather inaccurate, but only ofcourse if trust and livelihood do depend on it. Do you want to sell the rounds? Thats what JMB would be to risky for in my mind. Or is it rather private analysis and interest? Im not interested in this AR2 version because all my main projectiles are on a diffrent Plateau, but you might have other stuff that i could buy, and include in the Withepaper. Or you keep it and we pair my case design, propellant and Rifle with your Projectile, depending if there is the potential (as a Firebrand and JS-CTDG coop).

            I already had calculated ballistics and weight, but now added linked weight and pouch weight to my 3700fps version of the Ascendant (4th APEX). Weight’s less and has less recoil than the 3300fps version that i like to use as a balance version. From the same muzzle energy it has only a verry tiny bit less energy at 1200m, but flatter trajectory, reduced winddrift, stays even supersonic longer, increased fragmentation range. And ofcourse more energy per frontal area, and due to the mad velocity also incredible steel penetration.

            I currently make a bar diagramm with a lot of diffrent units comparing common and my developed rounds. Thats what i meant i want to send you. Ofcourse a ton of work, i couldnt stand any inaccuracy in it, because it has to be implemented later in a Whitepaper too.

            When i send it to you i now will also include a text with my current toughts on the interesting subject of optimum projectile velocity (advantages, tradeoffs, and new ideas/toughts).

            Man its 5:10 AM now, and im invited to a closing party at 1pm….
            Ammunition is just way too interesting.

          • Johannes von’ Strauch

            How the f* to you squeez 55grain into 3.75mm ….

            Please still consider tungsten is a no go for mass production. And for penetration you end up with EPR (steel copper), which dont have anywhere near the density.
            And bringing 55 grain trough a tiny 3.75mm bore to ANY good velocity requires a looong barrel.

          • noob

            ah. darn the surface area on the back. it’s like a skinny hydraulic cylinder vs a fatter one.

          • Johannes von’ Strauch

            jup…
            Material density constrains and bore volume kills it.

          • A 55gr 3.75mm projectile would have to be hella dense.

          • noob

            yeah – super long and thin, like a needle or a flechette, except spin stabilized rather than fins

          • I doubt you could spin stabilize it. I have an 0.166″ (~4.2mm) monolithic CETME projectile I designed for another project, and it would weigh 48.5 grains if you made it from WC. That’s about as long and dense as a small arms projectile can get. You could make a heavier 3.75mm projectile, but it wouldn’t be low drag.

            Remember, anything over about 7 calibers long can’t be spin-stabilized. And that limit is really more like 5.5 or 6.

          • noob

            Please pardon my ignorance, WC? Wadcutter?

          • Tungsten carbide, chemical sign “WC”.

          • noob

            Ah! thanks!

          • noob

            also if rounds of cheap AP on target rather than absolute accuracy is the focus of the future, could you have a barrel-less repeating arm that looks like a shield because it is one? eg: – a thick shield to protect the user from high explosive shock as a very small explosively formed penetrator cartridge drops through the “breech” in the middle of the shield’s surface and is locked away from the user.

            When the EFP fires, a light weight metal penetrator leaves at detonation velocity – as high as 30,000fps – to impact the target.

            Because the cartridge is so small (like pistol cartridge size) and the shield is so massive, it is a safe-ish proposition. Also you can hide from return fire behind it.

            https://uploads.disquscdn.com/images/73da2732de83dfaa06db905c00eaf53cd5a3529c7618d743dc894980a794e42c.jpg

          • I rather think you could do this with 40mm. Seems worth trying.

          • noob
          • Tassiebush

            Sounds like a half sibling of Project Orion

          • Johannes von’ Strauch

            Bye the way, isnt it quite late right now in the US..? You should go to bed.
            (gone for about 3hours now)

          • I often keep odd hours.

      • noob

        hmm. sounds like the G11 caseless.

        • Johannes von’ Strauch

          The G11 didnt achieved 3700fps, nor is Nathaniels round caseless.

        • It’s lighter and much faster than that.

      • Stuki Moi

        That is, at least per my estimation, the way to go. Kind of an HK 4.6 developed with a longer barrel in mind. Armor is only going to get better, so while 3700 may seem excessive right now, it may not remain that way forever.

        Unless the “big bullet crowd” can find a way to get their projectiles through armor, their fits really don’t much matter anymore. AP already is, and will only continue to get more, non negotiable these days.

        I’m kind of a “big bullet guy” myself. Based on what I’ve seen on game, I strongly believe wound channels through flesh, measured by bleeding, increases way above linearly with increases in bullet diameter, given similar bullet design and velocity.

        But it just doesn’t matter, once armor is introduced. First rule of terminal ballistics, will always be to make contact with what/whom-ever you want to terminate. If your 9.3×62 can’t get past a moose’s ceramic fur, you may as well miss. And as nice as a highly terminally effective round is, diminishing returns considerations still means you are, at least against human opponents in combat, 90% of the way from a miss to a hit with .50bmg, by simply scoring a hit at all.

        The biggest problem with small bullets, is that they don’t perform well at quickly stopping someone, which is what you often need in a CQB scenario. A hit with a small round, will likely mess up someone 500 yds away, sufficiently that his effectiveness as an opponent is severely reduced. But at close range, you need a stop right now. And 4.6 just doesn’t do that as well as .45. And neither will, I believe, your 4.85 vs a .30. So you need a delivery platform that facilitates multiple fast hits with the smaller bullets. Again, HK went through all those deliberations when developing the 4.6 and MP7. Just not for the more expansive set of uses faced by a main battlefield small arm.

  • NMhunter1371

    I don’t see why TFB is up-in-arms over 7.62×51 in a “battle rifle.”

    Waaaaaay… back in my day (EAS 2013) Marines were still patrolling with 240’s… Seems like a few select fire battle rifles could largely replace those roles and lighten things up quite a bit.

    Units were starting to field the M27’s at the time as well. Which, if I’m not mistaken, was to replace the 249… Seems like the Marines got it right for reducing the weight of the light machine gun and the army is doing right by medium machine guns… Were just calling it a “battle rifle” since it doesn’t used linked ammunition.

    Crew serve weapons can still have their place in the defense. Just this POG’s $0.02

    • ARCNA442

      You really can’t replace a machine-gun with a rifle no matter what the caliber is. LMG’s weigh 20+ pounds because they are built for reliable sustained fired and, when tripod mounted, they can do thing rifles only dream of.

      The M27 came about because the M240 is a pretty bad design that doesn’t really have all of the capabilities of a true LMG while still slowing down the man carrying it. Even then, the Marines are still keeping them in reserve.

      • Kivaari

        The M240 is a great gun. It was never intended to be a LMG, it was always a GPMG or what used to be called a medium machine gun.

        • ARCNA442

          Mistyped there – meant the M249.

      • NMhunter1371

        Exactly… make an closed bolt 7.62 version of m27 IAR… in fact I believe HK already makes one.
        Keep the true machine guns behind sand bags, send out practical lighter weapons on patrol.

        • ARCNA442

          If you want rifles bring 5.56, if you want machine guns bring 7.62 (or 6.5) and don’t try to combine the two because it won’t work (as the militaries’ many attempts since WWI have proven).

          • NMhunter1371

            The M27 works great!
            I see plenty of fully automatic “rifles”
            I’ve never seen a 7 pound “machine gun”

            Massive improvement in mobility(M27 is half weight of 249) far outweighs the 249’s edge in firepower(linked ammunition)
            But once again this is only on paper, 249’s in the sandbox rarely make it though 100 linked rounds.

          • ARCNA442

            I’m fully in favor of the IAR concept (though I’m not sure why they couldn’t have just used another M4), but it’s not a machine gun and can’t do the things that a belt fed crew served weapon with quick change barrels can.

          • NMhunter1371

            Most foot patrols aren’t sending out their machine guns with tripod or T&E. Most gunners are leaving their spare barrel under their cot since they usually aren’t taking more than a 600rd fighting load…
            All of a machine gun’s benefits shine in the defense and usually get left behind on patrol.

    • LGonDISQUS

      Crew are carrying an inordinate amount of stuff these days, if you thought yours was bad… add fifteen pounds of batteries and a full ar500 kit.

      • NMhunter1371

        Maybe times have changed. I remember 123 batteries being a scarce commodity.

    • CommonSense23

      You cannot replace a belt fed weapon with a magazine fed and expect the same amount of performance. It just cannot. And battle rifle is the term for full power cartridge select fire mag fed cartridge. People are up in arms over this cause it’s absolutely idiotic talking like we need to equip people with more powerful rifles.

      • NMhunter1371

        Except the 249 hasn’t performed as promised. The Sands of Iraq and Afghan taught us the limitations of open bolt weapons.
        The M27 has absolutely been more reliable and lighter than the 249. With typical fighting loads(300-600rds) you don’t need barrel changing capacity of a true machine gun. Again I’m not saying s@$@ can the belt Fed open bolts, just leave em in the rear.

        • CommonSense23

          Except they have lived up to expectations in Iraq and Afghanistan. I spent a lot of my time carrying belt feds. They work if maitained. They work great actually. The problem is the vast majority of the military is bad at maintaining there weapons. Cleaning them till they are shiny. Great at. But actual maintenance is generally pretty bad overall. Maintenance is knowing how many rounds the gun has. When the last time parts were changed. When to change parts. Thats maintenance. Which is something the M27 is going to be struggling with in about 5 years. I’ve carried a MK46 and 48 thru extremely dusty situations. Worked fine. Never a malfunction.
          And if you think barrel changes are the key to a belt feds suppression. You really have no clue what you are talking. With my old 46 and a 200 round box. A guy with a M27 has to do 6 reloads to meet the amount of fire I can put out without reloading. A guy with a M27 shoots half a mag for suppression trying to keep somebody’s had down. Has a half empty mag he needs to figure out what he wants to do with. I got 15 rounds left on my belt. I can start reloading the first chance I get, without downloading my weapon. And please tell me what exactly the M27 offers over a free floated M4A1 real world?

          • NukeItFromOrbit

            I’ve got to assume that the USMC will treat the maintence of the M27 as they do a rifle versus the abuse they seemed to have heaped on the M249.

            Why the USMC has not procured a reliable quad-stack 60 round magazine for tor the M27 remains a mystery to me and makes me think they are more interested in it as standard issue rifle. Apparently the USMC’s mindset regarding the concept of a squad automatic weapon hasn’t advanced much beyond slapping a bipod onto a M16A1 and flipping it to full auto.

          • NMhunter1371

            I believe the Corps is currently testing the Magpul 60rd mag… which would close some of the gap in perceived shortcomings. Read above for major differences between M27 and M16/M4

          • Because no reliable quad stack 60 rounders exist.

            The USMC has looked at PMAG 40s and DMAG 60s, but frankly, they have found that 30s work pretty well for the IAR role.

          • NMhunter1371

            No argument that a properly maintained and lubed 249 CAN be reliable…
            But I recall keeping are machine guns “bone dry” in country… and carrying around water bottles full of CLP
            M27’s are just as enclosed as an M4/M16 and just don’t adsorb dust and dirt like open bolts.
            And the M27 offered a heavier 16 inch barrel, a piston driven gas system, fully automatic fire, and a free floated barrel. They had chrome lined barrels that could actually shoot. Much more accurate than M4’s.
            I’ve actually wondered what they’ll do to equalize scores if they start issuing M27’s to certain units as GP rifle. (Rifle range scores have a large impact on NCO promotions)

          • CommonSense23

            First of all. Lets talk about the IAR. The fact that you think the 416/M27 is much more accurate than the M4 is laughable. It’s not. The M4A1 has a chrome lined barrel. The military already has free floated M4A1s. If you compare a free floated M4A1 to a M27 both shooting MK262. You are going to see the same grouping. The M27 and M4A1 are both limited by the ammo they shoot. So what again are you getting by going to the M27.
            So your point about belt feds is you didn’t have maintained weapons. So you should adopt a weapon that has a higher maintenance requirement than the M4?

          • NMhunter1371

            I’m having to stretch my brain back a few years but I believe the reason for the M27’s superior accuracy was the heavier/stiffer barrel and HK patented chrome plating process that resulted in much greater uniformity in chrome plating thickness.
            I’ve never shot an IAR but I did get to shoot the M32 before it was fielded and talk to some high level acquisition Marines in the process. They said the M27 was accurate enough to double as a DMR… I believe 1.5 MOA was the accepted accuracy benchmark… which is pretty dang good by military standards

          • CommonSense23

            The M27 is as accurate as M4A1 with a free floated barrel as long as both shoot the same ammo. NSW snipers are using the M4A1 as a sniper platform currently. And they use a optic that actually makes sense. The M27 accuracy people rave about comes from testing it with 262. Which the M4A1 barrel will achieve the same precision.

          • NMhunter1371

            I don’t know a thing about NSW. But after a quick google i think your probably referring to the MK12 which has a free floated, match grade, heavy barrel with a 1/7 twist(for those heavy 262’s). From just the spec sheet It would appear that the MK12 would have the edge in accuracy against the M27. And Wikipedia claims that some of these were in fact built on true M4 lowers and with select fire trigger groups…
            So your right-ish…
            The rest of the military gets the standard M4a1 which has a mil-spec barrel that’s definately not match grade, an 8-10 lb trigger, and non free-floating hand guard.
            So no, the M4a1 is absolutely, positively not as accurate as the M27. But, the MK12(which is built off of M4 receiver) is most likely more accurate than the M27.

          • CommonSense23

            No I’m not. I’m talking about the M4A1. NSW is using the M4A1 with DD rail as a replacement for the MK12. Again The M27 doesn’t have a match grade barrel. The M27 doesn’t have a match grade trigger. It doesn’t even have access match grade ammo. Its puts up the same accuracy as a M4A1. When you use the same ammo. Again the M27 isn’t that precise as you think it is. It’s not outshooting a M4A1 when both are shooting the same ammo.

          • NMhunter1371

            Ok, well I think it’s safe to say I’m not going to win you over on M27 being more accurate.

            Maybe you should look into a job @ USMC acquisitions…
            Sounds like they need someone that hasn’t drank the HK cool aid.

          • Trust me, they have them. Can’t say a lot more.

    • Guys… I’m gonna come out of the closet… As someone who also thinks the SAW is probably not a good idea.

  • nova3930

    Thought experiment for a theoretical cartridge building on something I was thinking about in the 7.62 Rifle RFP post. Assume you have a weapon originally tailored for 7.62×51.

    Now step down to a cartridge that’s the same OD as 5.56×45 but longer with appropriate powder for optimal burn, utilizing the 77gr SMK like MK262 does. There’s about 12mm difference in max OAL between 5.56 and 7.62 so what if you went to say a 5.56×50 or 5.56×55? What does that look like in a ballistic sense? Both muzzle velocity and down range performance.

    Cons I see are a heavier platform, somewhat increased recoil and maybe greater component wear rates. Might even have feed/extraction issues although I’m not sure.

    Could you hit the 80gr midpoint and get enough performance increase to outweigh the cons?

    • Kivaari

      Or something like the .22 Nosler requiring a new barrel and magazine.

      • nova3930

        Didn’t think about 22 Nosler but that’s probably a no-go with DoD. Nosler only claims 4k rounds barrel life as a plinker….

        ETA

        Which probably translates over to my proposal above. Not sure though…

        • Kivaari

          4,000 rounds is pretty poor. Even I could wear out a rifle on my limited budget.

        • Kivaari

          Or a 6.X/.22 Nosler.

          • ostiariusalpha

            6mm Nosler would be an interesting combat cartridge. Especially if they magazine’s internal COAL was increased a bit.

          • 6mm wildcats based on the 6.8 SPC (which is essentially the .22 nosler case but with a larger rim) can drive an 85gr @ 2950fps from a 16″ barrel.

            And with a brass case and 85gr bullet, 6.8 SPC is already at 15g – with hybrid polymer/steel, or aluminum/steel like Shell Shock’s new 9mm, we’d likely hit 12g – equal to 5.56, but with a good deal more range and power.

          • ostiariusalpha

            Right, the SPC would be the one to go with for a parent case. I still find 6mm SPC wildcats (like the 6mm-6.8, 6mm DTI, and 6mm WOA) a little stubby in their bullet selection for what can be had in the .243 caliber. If someone made a metal mag for the LWRC Six8 magwell, you could get a really decent amount of COAL to work with. Not necessarily a lot heavier bullets, but longer ogives would be ideal.

          • What we really need is something like rumored AMU “AR-12” with an intermediate length magwell size between the AR15 and AR10, designed for 6.8 SPC based VLD wildcats. .22-6.8 90gr VLD’s, 6mm 100gr VlD’s, etc.

          • I like the various 6mm SPC wildcats. They look fairly promising.

          • Hm, says Harrison. I am not so sure. I mean, I am sure you can handload them that hot, but I am a little skeptical you can create a military spec that consistently gives you that performance. Remember, these are two different matters entirely.

          • Really, the 6.8-wildcats are a useful weight / velocity data point, not the end goal for what the cartridge should be.

            I’m sure you could hit the goal of a 6mm 85gr @ 3,000fps, either with a hotter loaded 6.8 in a more robust firearm (ie AR-12, not shoe horned into a weapon built for 5.56.) Or ideally, by developing a similarly sized case purpose built for running at 62kpsi (small rifle primer, slightly beefed up brass.)

            For example, the basic 6×45 wildcat (.223 necked to 6mm) can hit 2750fps with an 87gr out of a 16″ barrel.

            Meanwhile, the SSA 6.8 SPC launches an 85gr Barnes TSX at 3030fps from a 16″ barrel.

            So between the two, plus our data from the adventures of the 6-6.8 wildcatters, a 6mm 85gr @ 3,000fps doesn’t seem that outlandish.

          • Johannes von’ Strauch

            Tell me your bullet lenght, full case capacity and OAL, then i calculate it for you.

          • Bullet is based on the Cutting Edge 88gr solid copper, which has a .445 G1 BC and 1.036″ oal, as that seems like the closest off the shelf projectile to the theoretical 85gr EPR. 6.8 SPC case, 62kpsi, lets say loaded to 2.5″ OAL for the “AR-12.” Thanks!

          • Johannes von’ Strauch

            Forgot it for a moment, had to calculate a ton of other stuff.

            About 2905fps (16.5″ barrel, with an unrealistic high case capacity of 6.8spc not 6!).
            And 2859fps just with some thicker 6.8spc brass therefore a bit less capacity.

            What i dont get, why in the world do you want to have a round, that doesnt fit in currect Rifles.
            And when buying hundret thousands of new Rifles totally waste the enormous potential of CT….. And then be stuck with junk.

            Also solid copper is – uncrealistic, use an EPR. Actually pretty simple… choose your steel penetrator volume (1/4 or 1/3) than calculate the densitys of copper+copper+steel : 3
            Put it into % compared to pure copper, take that % to calculate the EPR weight of the solid copper… = roughly 84,4813153961 grain.

            And… use G7 BC’s, G1 really kinda sucks. G7 already is inaccurate enough.

          • Johannes von’ Strauch

            Even with IMR powder, against a 62grain 5.56 with ball powder at medium velocity, it only has ~ 82% the Recoil/Joule efficiency. Which gets even worse when using similar powders.

          • Johannes von’ Strauch

            Even at an unrealistic case capacity of 6.8 spc (case mouth would be smaller smaller which would reduce case volume), a (not fully optimized) 85grain EPR projectile (flatbase to ease calculation, and only 1/4 penetrator volume to increase density therefore minimize seating dept), even at barrel burning 62000psi doesnt really want to move past 2850 fps.

          • Johannes von’ Strauch

            *i meant 2870fps. But as said, even in unrealistic overestimations it doesnt reach 3000fps.

          • Johannes von’ Strauch

            * also used 16.5″ barrel not 16″

          • Keep in mind, I designed the 6mm Bugzapper to prove a point to Tony. I didn’t design it as the ultimate round to end all rounds. IMO, it’s a bit large for a rifle round.

          • 6mm “a bit large for a rifle round” certainly sounds preferable to 7.62×51/.260 Remington battle rifles.

          • Well, everything has to be designed for requirements. IMO, the 6mm BZ satisfies requirements that are excessive for the rifleman, and probably DM as well.

          • The thing is, if a round is going to replace 5.56, then it has to offer a serious performance benefit – and simply being lighter does not seem to be an attractive proposition. Especially in an ‘overmatch’ era.

            So then the question is, how do you offer as much performance as possible to satisfy the acquisition process and placate the overmatch crowd, while at the same time having a round with reasonable recoil, magazine capacity, and weight characteristics?

            Really 6mm BZ/CAKE is the best bet for that if we’re not talking a novel projectile design like the AR2.

            Using the ‘Range to 1700fps’ comparison (since we can’t really compare ceramic or cmu defeat) – 5.56 is 475yds, 5.8×42 is 600 yards, and 6mm BZ/CAKE is 700 yards.

            With the 5.8×42 right there in the middle, I seriously doubt anyone is going to be able to sell a round with less performance then the 6mm.

          • “The thing is, if a round is going to replace 5.56, then it has to offer a serious performance benefit”

            Well, some people feel that way. Not sure I do. I think, regardless, selection of the next caliber should not be made based on feelings. So that means, figure out what performance you need and create something lightweight that meets those requirements. As far as I can tell, the 6mm BZ is too powerful for a reasonable set of requirements, but many people disagree with me.

            “and simply being lighter does not seem to be an attractive proposition.”

            Too bad. Weight is by far the most pressing issue.

            “Especially in an ‘overmatch’ era.”

            Screw those people.

            “So then the question is, how do you offer as much performance as possible to satisfy the acquisition process and placate the overmatch crowd, while at the same time having a round with reasonable recoil, magazine capacity, and weight characteristics?”

            You don’t. You tell them to go pound sand.

            “Really 6mm BZ/CAKE is the best bet for that if we’re not talking a novel projectile design like the AR2.”

            The 6mm BZ was designed to meet Emeric’s 600m criteria while offering a round with 1,000m GPC-like performance as a way to check how Tony (and to a lesser extent Emeric) felt about calibers smaller than 6.35mm. Basically, it was “here’s a round that does all the things your GPC is supposed to do but better, and it’s in a caliber I’m pretty sure you won’t like for entirely irrational reasons and I want to see if you’ll take the bait”. And he did. He came up with some BS justification for why it wouldn’t be a good solution. So the 6mm BZ did exactly what it was designed to do, and that’s it.

            “Using the ‘Range to 1700fps’ comparison (since we can’t really compare ceramic or cmu defeat) – 5.56 is 475yds, 5.8×42 is 600 yards, and 6mm BZ/CAKE is 700 yards.”

            I’m pretty sure you just pulled 1,700 ft/s out of nowhere. We’ll have a better established frag limit for M855A1 soon. I have some people working on it.

            Yes, the 6mm BZ is high performance, it was designed to be. But if the performance is excessive and that is costing you significantly in weight, then something should change.

            “With the 5.8×42 right there in the middle, I seriously doubt anyone is going to be able to sell a round with less performance then the 6mm.”

            Hold my beer.

          • While I appreciate you sticking to your guns on the relentless pursuit of weight savings, and telling the “overmatch crowd to pound sand,” this is a pretty risky strategy.

            To my knowledge, you’re the only one of any prominence advocating for weight savings over all. Meanwhile, the concept of “overmatch” is gaining ground in the military – a recent solicitation for white papers on cognitive performance actually used the term “cognitive overmatch,” to give you some idea of just how far this idea has spread. And the Army is studying exoskeletons rather then switching to 15lb plate carriers and lighter assault rucks…

            On the broader field of military acquisitions, ‘mo power, mo deadly’ has been selling programs since 1945. Im unaware of any similarly comparable level of enthusiasm for the ergonomics of the soldier.

            So you really have to ask, if you completely ignore the “overmatch” crowd, and then you don’t gain your own rabid following in acquisition circles, what are we going to be left with? The answer is battle rifles.

            Emeric and Tony started warming up to the 6mm BZ once it was pitched as the CAKE (which really is a better meme for viral infection) once the “have your cake and eat it too” aspects were pitched. There’s a decent chance that the 6mm’s impressive #’s, plus the have your cake and eat it to argument, would be persuasive enough to get people to back away from the ledge of full battle rifle.

            Regardless though, it’s time for you to pick something, or perhaps 3 clearly defined somethings, and advocate for them from your bully pulpit.

            If you want to effect positive change, it’s not enough to have 100 articles saying in detail what the Army is doing wrong. You need to offer concrete, easily acted upon solutions as well.

            You need to go through your vast array of cartridge designs, pick 3, and present them as alternatives soon, before this battle rifle train picks up any more speed. And ideally, at least one of those should be the 6mm BZ, but presented as the CAKE, since it’s easy to understand and offers something for everyone.

          • “While I appreciate you sticking to your guns on the relentless pursuit of weight savings, and telling the “overmatch crowd to pound sand,” this is a pretty risky strategy.”

            It’s the only strategy.

            “To my knowledge, you’re the only one of any prominence advocating for weight savings over all.”

            That tells me I am likely doing the right thing.

            “Meanwhile, the concept of “overmatch” is gaining ground in the military – a recent solicitation for white papers on cognitive performance actually used the term “cognitive overmatch,” to give you some idea of just how far this idea has spread. And the Army is studying exoskeletons rather then switching to 15lb plate carriers and lighter assault rucks…”

            The Army always searches for equipment solutions to problems, regardless of whether they are equipment problems or not. That’s their nature. I know I’m going to lose short term. Any sensible proposal will lose. This is a long game, it always has been.

            “On the broader field of military acquisitions, ‘mo power, mo deadly’ has been selling programs since 1945. Im unaware of any similarly comparable level of enthusiasm for the ergonomics of the soldier.”

            I don’t care.

            “So you really have to ask, if you completely ignore the “overmatch” crowd, and then you don’t gain your own rabid following in acquisition circles, what are we going to be left with? The answer is battle rifles.”

            We’re going to be left with full power rifles anyway. Or did you miss that ICSR is already happening?

            “Emeric and Tony started warming up to the 6mm BZ once it was pitched as the CAKE (which really is a better meme for viral infection) once the “have your cake and eat it too” aspects were pitched.”

            At this point, their opinion is not important. They’ve (Tony in particular) already done their damage.

            And as I said, the 6mm BZ was designed for no other reason than to get Tony to make a particular response. It wasn’t designed to have “meme magic”.

            “There’s a decent chance that the 6mm’s impressive #’s, plus the have your cake and eat it to argument, would be persuasive enough to get people to back away from the ledge of full battle rifle.”

            No, it isn’t. ICSR is already here. We lost the war for this ten years ago. The only game now is the long game.

            “Regardless though, it’s time for you to pick something, or perhaps 3 clearly defined somethings, and advocate for them from your bully pulpit.”

            I don’t really think so. Right now I am advocating for some easily communicated priorities rather than a pet round:

            1. Reduce the soldier’s load

            2. Requirements, not performance

            3. Don’t sole source

            I’ve been at this a long time. I’ve been participating in the ammunition conversation since 2007 (I was sixteen then), and I’ve been blogging here since 2014. I think I have a good sense of how people react to different proposals. Do you think if you propose 6mm BZ/CAKE that everyone else will keep a specific performance set, case head, bullet shape, etc in their heads? No, you will just be advocating for 6mm Anything. This is what happened to Tony, too, though he won’t admit it. Normal people (not ammo geeks) can’t keep all that data in their heads, they go by names. So 6mm, what’s that? 6mm Creedmoor, .243 Winchester, something like that. Maybe 6x45mm. None of them are what you want. You need to advocate for something different. So I am advocating for priorities instead. If the priorities are taken to heart in the long run, then I will trust the engineers to design good ammunition around them.

            “If you want to effect positive change, it’s not enough to have 100 articles saying in detail what the Army is doing wrong. You need to offer concrete, easily acted upon solutions as well.”

            I am doing that. What are you doing?

            “You need to go through your vast array of cartridge designs, pick 3, and present them as alternatives soon, before this battle rifle train picks up any more speed. And ideally, at least one of those should be the 6mm BZ, but presented as the CAKE, since it’s easy to understand and offers something for everyone.”

            Yes, I am sure the key to getting Army brass to take me seriously is to talk about cake. /sarc

            If you want to advocate for your round, do it. Don’t sit there and fart about on Tony’s forum, nobody reads that. Get a platform. If that’s what you think ought to be done, go do it. Don’t tell me to do your work for you.

          • R. Reynolds

            I don’t know why the 6×45 hasn’t been looked at. It’s a round that has been around for a long time. You could use the same platform with just a barrel change. Using a 80-90 grain bullet would meet nearly if not all the requirements.

          • I think generally speaking the 5.56mm gives better performance. So 6x45mm isn’t worth it, especially if we’re talking a retrofit.

            6/5.6x50mm magnum has some promise, though.

          • R. Reynolds

            Shooting the same grain of bullet the 6×45 shoots faster. Then you are able to use a heavier bullet with a higher B.C. I don’t see how you would consider that to be lesser performance.

          • Omega

            Heavier does not mean more bc out of nowwhere…. With a shorter ogive the form factor (shape) gets much worse and even with more weight the bc does not increase. Also then its a totally inefficient bc. Also less recoil efficient.

            Also for an non existent or mediocre performance diffrence its utter stupidity to waste millions for, and are unable to use NATO standart ammo around the world.

          • R. Reynolds

            If you think that a 6mm does not have higher b.c.’s than 5.56 you should pick up a reloading manual. I am not suggesting to replace it for no reason. If you do more research on the subject they are considering going to a .264 USA. Where’s the NATO support on that. All I was saying if you want a harder hitting caliber with more range and be able to keep the same combat load there is no need to reinvent the wheel.

          • Omega

            6mm can have a higher bc than 5.56×45 yes – not with a bad shape tough. If we are speaking about 6×45 in a 5.56×45 OAL Rifle. its performance is WORSE. The ogive lenght of 5.56 is already too short, so with a larger diameter the ogive lenght in calibers is WORSE, therefore the form factor becomes incredible bad and its aerodynamic goes down all over again.
            6×45 makes serval things worse, is less efficient. And prevents to use NATO ammo around the world.

          • R. Reynolds

            Last comment on the subject. If the 6mm bullet is such a poor performer, I wonder why it’s so popular in the long range competitions.

          • Omega

            Dude, you really DONT get it right?
            If you have a lot of space left in your magwell, then you can use a well shaped 6mm bullet in a 45mm case. If you have an Ar15 Magwell OAL you have barely 12,4mm left for your nose ogive thats stupidly short for 5.56 already. With a 6mm (.243) bullet its unbelievable bad.

            You want a 3 to 3,5 caliber nose for good aerodynamics, but you only barely get a 2caliber ogive. That thing will slow down incredible fast, loose a ton of energy, and drop like a stone.

            6mm is popular with well shaped bullets, which… fit in a bolt gun.
            Otherwise you need to bring down case lenght a looot, you loose a ton of case capacity and chamber volume, so you get under 5.56×45 energy while having barrel burning pressures.

          • James Kachman

            “Too bad. Weight is by far the most pressing issue.”
            Yes.
            “Screw those people.”
            Yes!
            “You don’t. You tell them to go pound sand.”
            YES!

            Two things, extremely excited to see a better frag limit on M855A1, second, more details on 6mm BZ and the irrational reasons?

          • Here’s the thread where I lay it out: http://forums.delphiforums.com/autogun/messages/?msg=6327.437

          • I will copy Anthony Williams’ and EmericDaniau’s responses:

            Tony:

            “This is the key performance point for me. For a GPC to succeed it needs to be a credible replacement for the 7.62x51mm in the eyes of the users, otherwise they will continue to demand the 7.62mm. And the smaller and lighter the bullet, the greater the risk that it will fail to achieve this. The Chinese apparently discovered this the hard way with their 5.8mm – it is used in every weapon type, including GPMGs and sniper rifles, and was supposed to be the do-it-all round, but was reportedly rejected by the troops as a replacement for the 7.62x54R DMRs and MGs. No great surprise, given the similarity in size of the 5.8mm to the 5.56mm.

            Of course, the 5.56mm was also regarded as the “do it all” round for the section/squad in most NATO countries, until recent combat experience demonstrated that it was not up to the job. So now we have the NZ Army reverting to the 7.62mm for all its belt-fed MGs and reintroducing the 7.62mm rifle to the section in the form of the selective-fire DMW, and Turkey and India deciding to revert entirely to 7.62mm for the standard infantry rifle. In doing so, they are accepting much greater penalties in terms of weight and recoil than a GPC would bring, but they have evidently decided that these are acceptable costs to get the performance they want. ”

            Emeric:

            “Open the cartridge neck and make it a 6.5 mm with a 100-105 gr bullet, and you will have a round that (for less weight than current 5.56 mm):

            meet “suppression requirements” with less heat flux and better barrel life,
            will carry a heavier penetrator for the AP version,
            will suffer less from loss of muzzle velocity when smart people will ask for a 8″ SBR,
            will carry more payload when smart people will ask for an API round,
            could use 160 gr RN bullets when smart people will ask for a subsonic round,
            could use the 6.5 mm CBJ sabot & WC penetrator if smart people ask for a saboted AP load…”

            This and other discussions have led me to believe that many people who have made proposals are “locked in” to them and will not accept different solutions, regardless of how information changes. I say as much in Overmatch I:

            “Whether this is deliberate or not is unclear; what is clear is that “overmatch” expresses the goal of massively exceeding the performance of enemy weapons. Doctrine, requirements, and optimization criteria have largely been abandoned by overmatch proponents in favor of an organic approach based on feeling and perception. If proponents of this principle are presented with a hypothetical round that meets notional criteria for overmatch but that appears too small or weak, they will reject it. In contrast to the vagueness of the word itself, proponents of overmatch have very specific ideas regarding what next generation ammunition must – quite literally – look like. In short, “overmatch” acts essentially as an identifier for those who feel the modern SCHV paradigm – including the US 5.56mm, Russian 5.45mm, and Chinese 5.8mm – is too small and weak for the modern soldier.”

          • James Kachman

            Much appreciated! Their responses seem to be rather nonsensical, and while I don’t think 6mm BZ is good enough to replace 5.56, I *really* love the detail and vision evident in your works. You truly are a boon to the firearms community and the study of warfare.

          • Aw, shucks, James, I’m just alright. 😉

          • Johannes von’ Strauch

            I have respect for Tony because all the stuff he has put together in some of his longer and higher quality non cherry picking pdf’s (even tough theyr few). But man theyr both so damn ignorant and narrow minded, theyr stuck in theyr stupid 6.5 world. If they only would know what is possible and how 100+ grain will be total junk soon, i would love to see theyr faces then.

          • Kivaari

            You could shove the shoulder back a ways and still have increased powder capacity. Make it fit the existing magazine well.

        • int19h

          I wonder how much more would that be with a nitrided barrel.

        • Erm, that’s accurate barrel life with a plain steel barrel. Guarantee you you’re talking well over 10,000 with a military barrel and military standards.

          Barrel life for benchrest/long range comp/varmint hunting from a plain steel barrel =/= military barrel life

          • nova3930

            maybe. they cut that 4k number in half for a “competition gun” which I take to mean larger strings of fire. Expect a significant increase for CL 4150CMV but then a pretty big reduction for FA. I’d like to see it tested to satisfy my curiosity regardless….

    • KE

      There are rounds (0.23 to 0.232) using light cases in development with extreme aerodynamics. They fit in 7.62×51 OAL weapons. Have the same energy at 1200 meter with far less weight, recoil, winddrift and a much flatter trajectory. They also beat .264usa with absolute ease.

      .224 is not as optimal for such an OAL.

      • Not sure why you feel that way. A smaller caliber allows for more ogive and/or propellant space.

        • KE

          Good argument, but thats only dependant on case design.

          • I was assuming the same OAL.

          • KE

            Yes, same OAL ofcourse. Im speaking about case design to optimize chamber volume on a rather short case while still having a long ogive.

            (I also mean 7.62×51 OAL not 5.56×45)

    • iksnilol

      What about 90 grain 5.56 bullets in your theoretical extended cartridge? Should get good velocity retention.

      • 5.56

        The lead 90grainers will slatter like water at barriers and armor.

        • 5.56

          *splatter

        • iksnilol

          Just scale up the m885A1 design to 90 grains and have a carbide core.

          • 5.56

            Tungsten carbide is WAY to expensive and rare.

            And 90grain would be rather slow.

            Also what you describe is an 90grain EPR projectile not “the M855A1 scaled up” because dimension relations would change.

          • noob

            DU? once upon a time depleted uranium was waste and people got paid to use it for counterweights in passenger jet control surfaces.

          • ostiariusalpha

            Wouldn’t that be fun? Six mags of DU bullets sitting in pouches right on your chest. Just don’t play with them too much, or you’ll get the cancer. Doubt they’d be allowed on the practice range either. Bunch of Safety Sally spoilsports.

          • noob

            In the uranium decay series most of the elements are alpha and beta emitters which you can stop with the thin foil of the gilding metal jacket. (Don’t dum dum your DU bullets by cutting the jackets, that’s against the Laws and Conventions of Land Warfare, so both the Surgeon General and the JAG will be angry).

            The notable exception is Protactinium (91Pa). That is a gamma emitter and truly nasty stuff.

            so use similarly weighted copper/bismuth non-AP ammo that has a matched ballistic path for training. for war pull out the ballistically identical DU cored (plastic filler, copper jacketed) rounds and think of it as a hot potato. You don’t want to be the last one to catch it.

          • Fast Forward

            However; metallic vapour, resulting from an impact with a hard material is invariably less pleasant. You might need to also start carrying a respirator.

          • RetroG

            Heavy metal poisoning is why DU rounds make people sick, not the radioactivity. Uranium 238 (depleted Uranium) is less radioactive than a banana, its half life is measured in BILLIONS of years, about the age of the Earth.

          • Fast Forward

            Alpha/Beta was related to the comment from ‘noob’ above.

            “You might need to also start carrying a respirator.”……..Relates ‘particularly’ to the heavy metal toxicity route caused by vapour inhalation.
            Regarding radioactive material, with a long t/2, you should be lucky, but you might not.

          • iksnilol

            Yeah, but you get my point. 90 grains loaded to the lands isn’t *that* slow and extends the range of the cartridge considerably.

          • 5.56

            A 5.56 with optimized projectile shape will have only slightly less energy at range with better: Velocity, steel penetration, flatter trajectory, less wind drift, less recoil for the same energy.
            And… less weight per round.

            90grain = verry bad idea fairy

          • You can’t scale M855A1 up to 90 grains. It becomes too long and won’t stabilize properly.

            The heaviest 5.56mm EPR I have designed is 75 grains. 77 or 80 grains is perhaps possible depending on the exact shape and twist rate of your barrel.

            None of that really matters, anyway, because relatively light-for-caliber ultra low drag bullets are the shiznit.

          • iksnilol
          • 5.56

            As said… they splatter like water on every barrier and armor…

            And as also said, an 5.56 EPR with optimzed shape, has way better performance.

          • Yes, lead is considerably denser than copper alloy and steel.

          • Jath

            “This bullet requires a barrel twist rate of 1×6.5” or faster”
            Damn

          • nova3930

            So by light for caliber low drag, for 5.56 are you talking something like a lengthened 45gr with a nose cavity or what? Light ULD is not osmething I’ve ever thought about…

          • I’m working with a few bullets at the moment, and the light ULD one is about 55grs at .224″ cal. Based on the AR-2 Short shape.

          • 5.56

            Doesnt sound like great performance…

          • You’re basing that on the projectile weight alone? That’s a bit premature.

          • 5.56

            Basing it on ballistic coefficient and energy at range obviously, not weight. You underestimate me, thats a bit premature.

          • The AR-2 Short shape has an 0.836 i7 FF, what do you mean ballistic coefficient doesn’t look good? That’s like the lowest i7 FF of any military experimental rifle bullet in history. With a 55gr 5.56mm bullet, you’re talking a BC higher than M80A1.

          • 5.56

            At what velocity do you want to use it?

          • 5.56

            No thats not what i mean. Even tough one in a similar direction exist.

            I mean optimized shape, while having an EPR construction, and the resulting medium weight of it (which is under 90grain).

          • Tungsten is not viable as a standard issue projectile core. Too expensive, it’s a strategic material used for cutting tools, and like 90% of the world’s supply comes from the PRC.

          • noob

            It’s like when Captain America said to Black Panther “My shield is special. It’s made from a supermaterial called Vibranium.”

            And Black Panther said “We have lots of vibranium in my country. Sometimes we make weapons out of it and shoot it into our enemies.”

  • kwisatz-haderach

    You lost me at……………………MATH !!!!

  • noob

    Ha! and my friends said they said we’d never use math after high school because other people would do it for us. I’m so glad somebody finally said H*rmonic Mean on a family friendly website.

  • Brad

    Math is why I suggested 3 days ago in your article “7.62mm ICSR Replacing the M4?” that going back to 7.62×51 is a fail. I also suggested 7.62×35 (.300 Blackout) as an alternative. With a 115g bullet, .300 comes in around 14.1gr. Well within the lower end of your math problem.

    • NukeItFromOrbit

      And even worse long-range performance than the 5.56x45mm? How is that an alternative?

    • XT6Wagon

      um, why not go 7.62×39 and get the same performance without the risk of killing people if they mistakenly put the ammo in a 5.56 gun?

    • .300 Blackout gives you worse performance for more weight. Pass.

      • Brad

        Really? Might want to check the charts again. What you lose in velocity you gain in terminal ballistics (energy) down range where it matters. Also the change would only be a barrel swap. Might want to let the USAMU know “October 23, 2011, SSG Daniel Horner of the USAMU used 300 AAC Blackout to win his 4th USPSA Multi Gun National Championship.”

        • Yes, really. Pass.

          http://i.imgur.com/WP7VjWF.png

          • RetroG

            Based on the energy in your chart, M855 only beats the listed 300 BO from 250-550 meters. At that distance, shouldn’t the grunts be calling in artillery or airstrikes according to current thought?

          • A lot of people don’t think so, although I don’t really have a problem with the idea. Just note in general how similar the energy curves are. The .300 Blackout never has more than a 200 J advantage in energy. Big deal, especially when it’s larger caliber and therefore has a reduced penetrative ability at those energy levels.

  • TX223

    So, all roads lead to the 6.5 Grendel? Especially since the firing platform weight shouldn’t increase significantly.

    • TechnoTriticale

      re; So, all roads lead to the 6.5 Grendel?

      Only if you accept what are likely crippling preconditions:
      . generally conventional metallic ctg
      . M4/M16 lower magwell: constraining OAL and case taper
      . no interchange hazard with existing 5.56 weapons
      . STANAG mag sidewalls, maybe feedlips too
      . minimal changes to upper, BCG
      These factors are what have made the 6.8 and the Gren less than optimal today.

      A clean-sheet ctg really needs to be clean sheet, and needs to also contemplate when cased-telescoped, or entirely caseless might arrive, spawning yet another cycle.

      • noob

        Case Telescoped thankfully eliminates taper angst, because you can push through hopefully instead of extracting.

        Same with Caseless: with caseless you can’t stovepipe. you only need to use your ejector to administratively clear your weapon rather than every firing cycle.

        with present propellants the rounds might be fatter in diameter than present cased ammo.

        I had a crazy idea the other day: the navy tried and failed to make a liquid propellant gun for naval bombardment years ago. maybe we should bring it back?

        The bolt closes on a projectile that is in a plastic sabot/sleeve that has an extractor groove on it for administrative clearance. the sabot/sleeve is closed at the bottom so it will either exit the muzzle with the bullet or get pulled out backwards by the extractor (the extractor also headspaces the projectile).

        have an electrically driven piston that pressurizes a charge of atmospheric air, and then an ordinary automotive fuel injector squirts some diesel (or JP8 or anything runny and oily and flammable you can get your hands on) inside an arbitrarily large diameter chamber for as much ballistic efficiency as you can design into a shoulder fired arm.

        When the piston reaches top dead center the electric motor holds it there locked and a high energy spark ignition system ignites the fuel air mix and the only way for the hot gas to go is down the bore, pushing the bullet with it. The sabot sleeve can either discard or it could fly with the bullet to target, depending on how angsty you are about BC/energy downrange vs little bit of plastic harming bystanders up close.

        the electric motor rotates the piston, and unlocks the bolt. the electric motor also advances the belt to index the next bullet.

        The whole thing, batteries included, could be lighter than a GPMG but you can dial up and down the amount of fuel and even compression ratio on the fly to either raise or lower the recoil vs range.

        You could put it all into a package about as bulky as a modern industrial weed whacker. I will name it that “the weed whacker: electrically driven liquid propellant belt fed firearm.”

        • Marcus D.

          So what do you have, an automatic potato gun?

          • noob

            a belt fed, automatic, hypervelocity potato gun.

          • Smokemup

            But isn’t crop rotation a limiting factor?

          • noob

            Petrochemical based fertiliser.

    • No, probably not.

      Including mags, here’s what you can carry per kilo with each round (yes, assuming magical fractional mags, sue me):

      5.56mm: 63 rounds

      7.62mm: 32 rounds

      6.5 Grendel: 38 rounds

      6.5 Grendel allows you to carry only 6 more rounds per kilo than 7.62mm (25 per kilo less than 5.56mm), and has trajectory problems. At that point, why not use a decent caliber like .260 Remington?

      The reason 6.5 Grendel is so lackluster for mass is because it requires steel mags for an M4 retrofit. These mags are significantly heavier than either 5.56mm or 7.62mm magazines that are aluminum or polymer.

      You could of course say “well, let’s just use a totally new platform, with new magazines”. In that case, why are you using 6.5 Grendel? Retrofit is really its raison d être.

      Hypothetically, I suppose we could do that math anyway, though. This is assuming 30 round PMags that weigh 160 grains (just guesstimating here):

      6.5 Grendel (dedicated platform, PMags): 43 rounds per kilo

      So it’s now 11 rounds more than 7.62mm, 20 rounds less than 5.56mm. Still way closer to 7.62 than 5.56.

      You can use lighter bullets, of course, and there’s something to that idea, but it doesn’t decrease your weight all that much, nor does it give Grendel fans the “7.62mm-lite” ballistic charts they love.

      • Nathaniela

        Excellent analysis! Thats exactly what we love you for.

      • noob

        What is the no-compromises version of start-modest-and-retain-velocity Grendel? 6.5 Creedmore? (or is that too much for select fire?)

        • Depends what you want. The Grendel is designed for a pretty specific set of compromises tethered to the AR-15 pattern. If you’re not doing that, then the answer will depend on your requirements. There are a couple obvious “Grendel+” type rounds, though:

          .264 USA – Like the Grendel, but longer and faster

          6.5mm Creedmoor – Much longer, much faster

          The “6.5 Grendel but longer” concept has been suggested a pretty large number of times as “the right answer”, but IMO it’s not well optimized. Doesn’t make it a bad idea, it just depends what you want. Any of these rounds will probably be heavier than the Grendel, it should be noted.

          • Adam D.

            I’m not a big ammo buff, so correct me if I’m wrong,
            but doesn’t the 6.5CM have a lot shorter barrel life than .308 for instance? If so, even when just tossing around ideas, it wouldn’t be a great service cartridge for a general issue weapon where suppressive fire is a must.

          • I don’t think barrel life is a huge concern for military arms right now. Modern ammunition significantly exceeds requirements.

          • Adam D.

            I see, thanks!
            I was asking because from reviews of PRS guys and other shooters I’ve heard it quite a few times that 6.5CM has a noticeably shorter barrel life. What’s the expected service life for 7.62 barrels now in the US Armed Forces? I’m thinking of the M110 primarily.

          • Like 15,000 rounds plus for machine guns. The M110, I’m not sure, probably less just because the standards are different.

  • Isa Akhbar

    This discussion/argument will never end until new lightweight case technology is developed and adopted, like the Shell Shock hybrid case. It will also never end until Big Army decides exactly how many rounds their grunts are going to carry on a load-out. Before any of that happens, though, BA has to drastically reduce the weight of all the crap they’re expecting the human body to hump over the dunes. Drastically reduce. Then, they can carry all the ammo of whatever construction their hearts desire. Weapon, electronics, armor, food, water, ammo…what the hell else do they really need?

    • b0x3r0ck

      Porn…..toilet paper……maybe?

      • Isa Akhbar

        Ok…forgot those. Been a while since I was in sandland…

  • Tuxedokitties

    And yet there are neckbeards out there that thing a 12 ga shotgun is the best survival gun because toting around 1 oz slugs makes total sense…

  • Smedley54

    In selecting the 7.62×51 cartridge, DOD obviously has two things in mind: First is that it’s already an accepted NATO round, and second they’re counting on next generation materials (read that “plastics”) to replace brass and lower weight. A clean sheet design might lead to something like the 6.5 Grendel or 6.8 SPC – either of which is more controllable on burst – but the inertia of NATO politics disqualifies them.

    Nothing in this sounds helpful to the grunts already strained by their combat load. There’s got to be a better path forward.

  • therealgreenplease

    “Since this is a family friendly site.”
    😂😂🤣

  • mazkact

    Ah yes……..the ole harmonic mean.

  • Michael Blum

    I wonder if the DoD wants to leave space for guidance or bore-size-dependent payload. Steerable or shaped-charge rounds are down to about .50 cal size now — shaped charge effectiveness is diameter dependent. Combine those two features, squeeze it down to about 7.62mm bore, and a “hits targets, makes holes” outcome results. Along with “costs beaucoup money” and “training, Law of War, and legal restrictions are super annoying”.

    Ooooh, 6mm Lee returns in time to save the day!

  • Argy007

    After reading recent TFB articles and comments I have come to the conclusion that 6x49mm Russian Unfiied cartridge is the best suited cartridge for US army needs.
    It weighs right under 16 grams when loaded with steel core 77 grain bullet.
    (Take note that in the comments, Nathaniel mentions that 80 grains is the maximum acceptable bullet weight.)

    A flock of birds with one stone?
    – Best performance vs weight
    – 71mm max OAL to fit in 7.62x51mm rifles
    – 11.35 vs 12.01 mm case diameter, allowing for 25 round mags instead of 20.
    – Increased armor penetration to deal with level IV ceramics.
    – Increased range (overmatch).
    – Steel case weighs much less than brass case and is cheaper.
    – Same recoil impulse as 7.62×39, making it suitable for full auto fire.

    • Dude

      -> INSANE barrel burning and pressure

      +extremly inefficient bullet…

      Even tough it goes in a good direction, much better than slow and heavy gpc’s.

      • Argy007

        The bullet does have a low sectional density, but it has a perfect shape (enlargened 5.45×39) resulting in 1150 meter supersonic range, which is on par with .300 WM when loaded with 190 grain OTMs.

        Modern metallurgical advances can easily extended barrel life to 10k shots even with such crazy high pressures.

        • Dude

          Good and “perfect” is WORLD’s of a diffrence. Never call something perfect, if it isnt the best physically possible…

          “metallurgical advances” cost a ton, and will still cause inaccuracy when the barrel gets hot too fast. Also for a given barrel life with such a barrel, a more optimized round will have way more.

          Its too much, a smaller version of it with a more optimized projectile would be more usefull in Rifles.

          • Brett baker

            So you would object to an updated 6mm lee-navy, 130 at 2700?

          • Dude

            130grains? Too heavy. 2700fps? Too slow.

    • Argy007

      Although I think it would be a better decision to go with .30 Remington case to make 6x48mm instead, while increasing bullet mass to 85 grain and reducing velocity to 3000 fps.

    • I like the 6mm Unified, but for the rifle it has excessive performance, IMO.

  • idahoguy101

    You left out the 276 Pederson round that the original Garand rifle was made to chamber.

    Army Chief of Staff Douglas McArthur made Springfield Armory in Massachusetts redesign the rifle for the 30/06 cartridge.

    Ballistically it was similar to the later 280 British. If only the US Army had adopted the 7×57 Mauser instead of the more powerful 30 caliber cartridge of 1906!

    • I’m sorry, “left out”? Not sure what you mean.

  • Gus

    So I was just running around the internet and while I cant find the weight 6x45mm it looks interesting. It’s 80 gr (5 g) SP 2,650 ft/s (810 m/s) 1,248 ft·lbf (1,692 J). Yes its a soft point and not EPR but to me that looks like an ok but not great idea. In a way it’s something that the government would do just as a stop gap and not a solution. But with the idea of telescoped ammo it would work better.

    • Generally, you want to increase relative capacity and increase ogive space to improve performance beyond about 100 meters. The 6x45mm decreases both of those characteristics.

  • Ringo Lapua

    The 6.8 spc is my SHTF round.

  • Jaybird

    I think if they want some thing still small with power, The 6.5 Grendel is the best option.

  • crotalus

    What percentage of the cartridge weight is casing, and what is being done to reduce that?

  • ClintTorres

    Interesting…6.5Grendel is declared “overweight” by some while it’s half a gram heavier than 7.62×39. What armed force could possibly prosecute a war with that burden?

    Let’s not get stuck on a number, people…sheesh!

    • Instead of sarcasm, do the math. Look at the loads the infantry are already carrying. Calculate what the weight penalty is for these rounds. Do the work, and determine what your tradeoffs really are.

      My spreadsheet gives an average increase of 6.2 pounds per soldier if both 5.56mm and 7.62mm were replaced with 6.5 Grendel. Is that unacceptable? Depends. It’s not nothing. If you are trying to – at the same time – cut the soldier’s load by 30 pounds, now you have just made the already daunting task of cutting that weight 20% harder. What’s the gain? What are the penalties? Go look at them, then tell me whether you think they make any sense.

      Because I’m not seeing it. An increase in effectiveness is fine, but weight comes first. That’s the key issue that is impeding soldier effectiveness on the battlefield right now.

      • ClintTorres

        You’re absolutely right about the weight…no argument here.

        What I’m trying to point out is that the soldier’s load is a dynamic thing that is more than just a number. Sure it’s 6lbs more for the same number of rounds but aren’t there soldiers out there carrying 7.62×39 and 7.62×51 weapons and getting along just fine? We are highly adaptable creatures and there are plenty of soldiers who can make it work if the trade offs are worth it.

        I don’t claim to know what a soldier’s priorities are but I’m willing to bet that a cartridge in the same class as the grendel would make sense despite it’s weight penalty over 5.56 as evidenced by the grendel’s weight relative to 7.62×39(17.8 vs. 17.2g, respectively).

        Anyhoo, let’s not forget that the soldiers load will be decreased more rapidly as heavier rounds are expended…didn’t think of that didya? 😉

        • Clint, there are people out there with 7.62mm weapons who are carrying 110-120% of their body weight. I don’t really think the weight aspect is negotiable. Not to me, anyway.

          As for who carries 7.62×39… Well, who does? Not any NATO countries. Finland does, but they have a defensive force, and I am not sure they issue body armor like we do. Many third world countries do, but they certainly do not issue body armor. So the question isn’t “can someone carry 12 pounds of ammo?” – because of course they can. The question is “can someone carry an additional 6-8 pounds of ammo when they are already carrying 120 pounds of gear (which they are)?” I think the answer to that question is quite obvious.

          Don’t forget that 7.62x39mm is pretty much poo as a terminal performer. For some reason it has recently gained a reputation as a “manstopper” which is wholly undeserved, at least in its steel-cored M43 form (lead cored M67 is halfway decent). I imagine this is more of a “grass is greener” effect than anything else. It’s not fun seeing your buddies get shot, even if they get shot by something that wasn’t particularly nasty. Not fun being shot, either. But 7.62×39 is much less effective than 5.56mm in pretty much every measurable way, not more. Which means “6.5 Grendel performs better than 7.62×39, and is only a touch heavier” isn’t a terribly compelling argument.

          Doesn’t mean 6.5 Grendel’s bad (it’s not), but it doesn’t change the fact that it’s very heavy and optimized for the wrong performance band.

          “Anyhoo, let’s not forget that the soldiers load will be decreased more rapidly as heavier rounds are expended…didn’t think of that didya? ;-)”

          I did think of that. The problem isn’t how much they are carrying in a firefight, it’s how much they are carrying on marches and patrols. And if resupply is doing its job, then they’ll be back to carrying a full combat load quickly. So the total amount of time they are not carrying as much because of ammunition expenditure is in the big scheme negligible. Let’s also not forget that higher weight and bulk makes resup’s job more difficult, as well.

          • Brett baker

            So you weren’t impressed by the supposed superior anti- material abilities of 7.62×39?

          • No I would say not.

  • palehorse58

    I’m for giving every one a mini gun with a backpack loaded with about 3000 rds. This gives them about 1 minute of sustained fire. Their backup gun could be a Barrette 50 107 model. There is always a ma deuce around if you need ammo.

  • ……..

    .300 BLK?

    • 5.56

      Insanly stupid trajectory, wind drift, low point blank range, hilarious short supersonic range. + more recoil and weight. While also risking to blow up guns when ammo is mistaken by some random fool.

    • No.

  • richard kluesek

    So 7.62 x 39 is the answer ? About 1900 US army Ordinance was looking at 7mm Mauser, how does that compare ?

    • How did you come to that conclusion?

      • richard kluesek

        Comparing your photo lineup of 7 cartridges, 7.62/39 was the lightest after the 5.56/.223. While there is reported interest in a return to a “conventional” 7.62 round for reach and knockdown power your article brings up converse and unconsidered issues about the infantry grunts’ burden. Small calibers, 6mm, 6.5mm, 7mm all have been around and in use by the USN, Japan, Italy for the some of the first half of the 20th Century and your concept of small bore light weight is not unique to the 5.56 or 5.45 . May our troops have what genuinely is best whatever that is fairly determined to be.

        • 7.62x39mm has inferior performance to 5.56mm in virtually every respect and is closer to 7.62mm in terms of ammunition load per kilo… So how is it “the answer”?

  • scaatylobo

    I still believe that if it were not for the NIH syndrome [ not invented here ].
    We would have had about 30 years [ or more ] invested in making the 7.62 X 39 into an AMAZING round that would fill in all the voids .
    BUT since that is never going to happen,we will hash and rehash the same old B.S. about the 2 same rounds.

    • I am skeptical. What changes do you propose to 7.62×39 to make it not so mediocre as it is?

      • Kivaari

        The Soviets worked with the 7.62x39mm to improve it, it’s called the 5.45x39mm.

      • scaatylobo

        I know my limitations,and I am a muzzle freaking scientist.
        So I wont pretend that I could guess what the past FIFTY YEARS of investing in the intel into the 5.56 would have meant for the 7.62 X 39.
        But all the materials and all the powders and all the different bullet weights = might have been a HUGE difference in what they issue now.
        In fact I will go so far as to say that IF [ big if ] “they” had put all that money and intel into the ‘other’ round,we might not even be discussing the 7.62 X 51 at all.