Weekly DTIC: The Ultimate Caliber – Myth or Reality?

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This weeks’ DTIC document looks to frame a historical and technical context for the ongoing debate on general purpose infantry cartridges. A PowerPoint presentation by Shawn Spickert-Fulton of RDECOM, it provides a pretty solid framework for understanding rifle ballistics and the part cartridge design plays in it. While without the accompanying narration it seems a bit bare, the concepts outlined in the presentation do I think create a good starting point for the modern military small arms ammunition enthusiast to tackle some of the more advanced literature also available on DTIC.

The presentation covers:

– The design space for small arms projectiles across calibers from 4mm to 15mm.
– The design space for small arms cases, projectiles, and propellant charges as a unit.
– Why form factor matters.
– Projectile energy retention at range.
– Why velocity matters for point blank range.
– Barrier penetration and terminal effect.

As mentioned, this document is something of a teaser, as without Mr. Spickert-Fulton’s narration, the discussion of each subject lacks for depth. However, for the beginner, I think the document helps suggest what questions they should be asking, reducing “unknown unknowns” perhaps to “known unknowns”.



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 can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Paladin

    There is no ultimate cartridge, there’s just the best cartridge for the job.

    • Don Ward

      There is no “best cartridge for the job”.

      There are a number of similar and overlapping cartridges most of which have near identical performance and should be judged by a person’s individual preference, access to platforms and availability of resources.

      • TFB comments: Where Romanticism goes to die.

        • Zachary marrs

          It never even existed

        • Don Ward

          You know I’m the ultimate romantic. All guns need to have wood stocks, a lever and come chambered in calibers that are based on how many grains of black powder are needed to propel them. Clearly 30-30 is bestest!

          • Grindstone50k

            I’m sorry, I can’t hear you over the sound of my .45-70.

          • Cal S.

            What?…

            I don’t even…

            I’m going to hug my AR now.

        • dan citizen

          “TFB comments: Where Romanticism goes to die.”

          I stood in the doorway as if held in place by a great weight resting on my heart… inside was my past, 7.62×39, my stout, sweet Russian love. Simple and sturdy, she embodied all the salt of the earth simplicity and rugged beauty that my young body had craved. Not the least was her dark secret, her primer pocket was… Berdan… the forbidden primer. I had worked and probed that strange anatomy, sought past her subtle crimping to first lay eyes upon, and eventually to master, her tiny twin flash holes to set forth two tiny fingers of flame that filled her case volume with fire and warmth,

          But I could not stay, my youth had waned and like a shark I must swim forward or die. I know in the future I will be staring at a gun store’s shelves facing elevated prices and limited selection and with a wonderful pain, my heart will sing of Spam tins crudely opened, of strange foreign oils and cartridges in strange numbers spilling out. But it will be but nostalgia. Coldly I will press down these remembered dreams, take out my credit card, and shell out $45 for 20 rounds….

          Twenty rounds of what? Well therein lies the soaring joy that lifts my heart, and thinking of this unsticks time, I turn and stride out to my truck, for today at least, I will think of 7.62×39 no more.

          “How did it go honey?” She asks as we drive away.
          “it went fine 6.8 SPC, it went fine….”

      • Paladin

        There is a best cartridge for the job, it just depends on how specific you are about what the job is. Constraints such as availability, size and weight considerations, and platform specific limitations all factor in to the decision of what makes the best cartridge for the job. Personal preference on the other hand has no real impact on a cartridge’s ability to perform a given task within a given set of constraints.

        • Don Ward

          But most of what you are describing comes down to personal preference. What’s the “best” handgun “self protection” round? 9mm, .40, .45 ACP, .357 Magnum, .41 Magnum, .380 ACP? You can debate these but it really is a question of the platform the weapon is chambered in and how large or small of a handgun that you wish to carry.
          What’s the “best” deer rifle? .243, .308, 30-40 Krag, 30-06, 30-30, 25-06, 7.62X39, 7mm Magnum, etc, etc, etc et al? There are so many variants and so many rifle rounds that overlap and are interchangeable in terms of ballistics at different ranges that one would be silly to definitively label one or the other “best”.

          There are simply calibers that are more useful than others that it comes down to personal choice.

          • Paladin

            It’s entirely possible to establish which cartridge is most suitable for a given task without relying on personal preference.

            What is the best handgun round for self defense? It’s the one with the highest consistent wounding ability, capacity and accuracy that fits within the constraints of concealability, weight, and recoil tolerance. This does not mean that there is one best defensive handgun cartridge that everyone should be using, but that for any given set of reasonable circumstances there is a cartridge/firearm combination that will empirically perform the best.

            The best deer hunting round is dependent upon terrain, the hunter’s skill, and specific weight and recoil tolerance. There are many cartridges entirely suitable for the hunting of deer, but the various cartridges will perform better or worse in specific situations. Given appropriate terrain and sufficient skill the hunter will be able to close the distance with the deer, and less power will be needed, allowing optimization WRT weight and recoil. OTOH, where concealment is sparse and stalking is difficult a more powerful cartridge becomes necessary in order to make humane kills at longer ranges.

          • Don Ward

            Certainly. You don’t take a .22 Hornet out Brown bear hunting even though theoretically it can do the task. And you don’t take a .45-70 out to shoot Prairie dogs. On the other side of the coin, however, I can think of a half-dozen rounds that you can use to plink Prairie dogs or a half-dozen rifle rounds that can be used interchangeably for hunting Brown bears. Whats the best? It comes down to personal preference. I’ll take a 45-70. Not because it is a necessarily “better” round than any others but because of other categories like price, availability, range of reloading options and the fact that it comes in an anachronistic weapon system like the Marlin which has the weight, uses a familiar operating system and shoulders in a way that I prefer.

            What’s the better handgun cartridge? To me it’s .357 Magnum and this isn’t even a debate because in terms of ballistics it is superior to any of the options I listed up above (*thumbs nose at .45 ACP fan boys). But it comes in a revolver. I personally like revolvers for a variety of reasons that are not germane to the conversation. On the other hand folks are wedded to their semi-autos. But there again it is the size, feel, reliability, magazine capacity and personal choice that – to me – are more important than a discussion on whether 9mm, .40 or .45 ACP are better or best.

          • Paladin

            Factors like cost and availability are not a matter of preference, they are constraints just like size weight and recoil.

            To be clear, I’m not saying it’s wrong to select a cartridge based on personal preference. Many cartridges and/or firearms have a certain romanticism to them that is appealing, second kind of cool, as nutnfancy puts it. My point is that a simple rational comparison within the given constraints of necessity can be used to select the definitively best cartridge/firearm combination for a given specific task.

          • The best military cartridge is the one you can produce in the billions.

          • Paladin

            So the best military cartridge is .22lr? Or did the ammo shortage put paid to that?

          • The specification for M855A1 calls for a billion rounds per year, production. There’s probably more 5.56mm produced per year in the US than there is .22 LR, to be honest.

          • Paladin

            According to Wikipedia, annual production of .22lr is in the 2-2.5 billion rounds per year range. The question, then, is how much 5.56x45mm is produced for civilian shooters per annum.

          • A billion rounds per year is the minimum acceptable production value. More is produced every year.

            However, the 2-2.5 bil. figure for .22 LR actually surprises me.

            Regardless, it’s not even remotely outside the purview of centerfire rifle cartridges to be made in the billions per year.

          • Robert Kalani Foxworthy

            the best round is the one that does its intended job. there are plenty of jack of all trade rounds they have there follwoing but they are good at alot of thing but they dont excell at any one thing.

          • iksnilol

            Not really, I like .357 magnum but it isn’t really any better than 7.62×25/9×19. Sure, it has a bit more energy but with good bullets it doesn’t matter. + I don’t trust revolvers that much. I find them slow and hard to conceal (+ the grip is usually not well suited for fast follow up shots).

            Though that is my opinion and is what works for me. For other people it might not be the best choice.

  • Don Ward

    I want a firearm cartridge that is low recoil, has good penetration, a flat trajectory, hits hard, can reach out to a thousand yards, can be used to clear rooms, doesn’t over penetrate, is useful for hunting squirrels, deer, ducks and grizzlies, doubles as an anti-personnel/anti-materiel stopper and costs five cents a round.

    Come on ammo makers, it’s the 21st Century!!!

    • John

      Would you like a phased plasma rifle in the 40 watt range as well?

      • Mark

        Hey, just what you see pal…

        • Don Ward

          Well played sirs.

      • dan citizen

        DIY plasma cannons are pretty easy actually. Line up a bunch of capacitors, throw a handful of kilojoules through a couple CCs of water and POW! 15,000 fps… sadly electrode life is about one shot… or less.

        Light gas guns on the other hand can get 20 grain projectiles in the same velocity ranges with only a 12 gauge shell for a power source.

        https://en.wikipedia.org/wiki/Plasma-powered_cannon
        https://en.wikipedia.org/wiki/Light-gas_gun

    • 7.62mm soldier

      Such a cartridge was available in 1930 with the .276 Pedersen, during WW2 with the Japanese 6.5 mm Arisaka, in 1949 with the .280 / 7mm British, in 1970 with the 6mm US SAW. Today, the .260 Remington, 6.5mm Creedmore and 6.5 x 47 mm Lapua all offer performance in your suggested ballpark. All we need is an Army to adopt it. Given the US Army’s new Small Arms Ammunition Configuration (SAAC) Study announced last year, it seems that the question of calibre is again being considered. I am sure the study will recommend a caliber between 6.5mm and 7mm, just like every other serious effort to do the same over the last 100 years. The ammo makers can do just about anything the Army wants, so maybe what we should be saying is: Come on Army adopt it already! it’s the 21st Century.

      • Cal S.

        I’m still interested in the .25×45 Sharps (6.35mmx45mm). Gotta see how that turns out.

        • It appears to be designed to be legal for medium game in all 50 states. Besides that, it’s performance isn’t substantially different from 5.56mm.

      • I cover this issue extensively on my blog, and it does not make sense to switch to another caliber not materially different from 7.62mm NATO. Further, I do not know what the original context of the “most caliber studies suggest a caliber of between 6.5-7mm” line is, but it isn’t actually reflected in the historical record. I’d warrant that most studies in the 20th century suggest a caliber between 7-8mm, almost all of those being so far removed from the current state of the art as to be rendered completely irrelevant.

        The most thorough and applicable studies in fact recommend calibers typically less than 6mm.

  • st4

    Perfect cartridge: 10mm explosive-tip caseless. Mag tops off at 95 rounds. Not recommended for close quarters use on hostiles that bleed acid.

    • allannon

      gyrojet, for reduced recoil

      • 1911a145acp

        gyrojet at close range……not so good.

        • allannon

          He already spec’ed explosive, so velocity doesn’t really matter. 😉

  • mikenz

    All Caliber/Cartridge options will be a pile of compromises at the end of the day. You want light recoil , but something that hits hard. Smaller calibers enable you to carry more rounds but again don’t hit as hard. Something that penetrates light armor or cover but is effective on humans as well. Commonality between rifle and machine gun ammunition. Accurate.

    The best compromise at this stage seems to be the 6.5 Grendel.

    • The 6.5 Grendel is not suitable as a military rifle cartridge.

      • Anonymoose

        It is better than the 6.8 SPC if you use 20″ barrels, and about the same if you use 16″. One of the major problems plaguing our infantry is that the Army is fixated on the M4A1 rather than the M16A4 (or the Marine Corps’s M16A5 concept) like they were 10 years ago. If you just add an adjustable stock, then the full-length M16 becomes a lot handier and remains a lot more effective and reliable than an M4. Also, the 6.5 has the other benefit of using more common 7.62×39 boltfaces.

    • Cal S.

      5.56NATO M855 LAP has the edge in barrier penetration capabilities over the 7.62x39mm. For civilians who do not have access to AP 7.62 (thanks to someone’s lousy idea to make a rifle into a pistol because they could), then the 5.56 is the obvious choice.

      In the 7.62×39 vs 5.56 debate, everyone is ignoring the elephant in the room, which is the fact that the Soviets abandoned that cartridge for the 5.45×39. If the 7.62 was so world-beatingly awesome, why did they go smaller and lighter? Have you seen the wound cavity from a 5.45? It’s nasty looking.

      The only problems with the 5.56 that I can find in the research I’ve done is that it’s maximized to a 20″ barrel while the military keeps making barrels shorter and shorter. Like the aforementioned rifle-pistols, you’re going to get a marked decrease in performance. If they would make a round that would be maximized to a shorter barrel (maybe a longer bullet with a hollow tip and more powder behind it?), that would probably fix their problems.

      Regardless, for a cartridge that’s supposedly a ‘varmint’ round and spurned by our fathers as ‘ineffective’, it sure has sent along an awful lot of bad guys.

      • I agree; it seems to me that there are a lot of people who consider the adoption of 5.56 to be an “accident” or “mistake”, which doesn’t explain the 5.45 or 5.8mm.

        • iksnilol

          Russia hasn’t abandoned the 7.62×39. You got to know a bit about how the East works (it’s a bit complicated).

          IMO x39 and 5.56 are suited for different roles. 5.56 is good for millitary due to less adjustment needed for range/wind and light weight (soldiers carry a s***ton of equipment). While for civilians who shoot often (especially reloaders) 7.62×39 has more advantages. Short barrels, subsonic, barrier penetration. Plus the middle of the road stuff is cheap enough to become proficent without breaking the bank.

          IMO whatever floats your boat go for it while I go for what floats my boat.

          • In the United States, there are far fewer options for reloading 7.62×39 than .223 Remington.

            7.62×39 produces inferior ballistics at all barrel lengths to 5.56mm, and it doesn’t really retain energy any better at the shorter barrel lengths, either.

            The only thing that gives 7.62×39 its penetration advantage is the typically heavier construction of Russian projectiles. This can also be found in common imported 5.56mm projectiles, as well.

          • iksnilol

            Are you really going to argue that a 220 grain subsonic bullet is worse than a 110 grain subsonic bullet? Or that a 5.56 with a 12 inch barrel is more comfortable/less concussive than a 7.62×39 with a 12 inch barrel (with handloads you can get complete powder burn in 9-10 inches of barrel)?

            I don’t hate on 5.56 but for me and a lot of other people 7.62×39 has more advantages.

          • Any short barreled rifle is going to be extremely blasty.

            I am not saying people shouldn’t buy 7.62x39mm rifles; it’s for example an excellent deer cartridge legal in all 50 states and the vast majority of local jurisdictions. However, in military terms the 7.62×39 is essentially obsolete, the low emphasis on small arms in modern combat coupled with widespread availability being what keeps it going.

  • Zachary marrs

    I’m beginning to suspect that these DTIC posts are just put up to try and get us to argue

    But the best caliber is clearly the .40

    • st4

      The better bait would have been 30 Carbine as history here has shown.

      • n0truscotsman

        I thought frozen cotten jackets worn by NK troops couldn’t stop 30 carbine? I heard it from a couple of vets so I know is confirmed fact.

        • UnrepentantLib

          I’ve come across a couple explanation for why the .30 Carbine wouldn’t penetrate those cotton jackets. One is that some of the ammunition used in Korea was left over WWII stock. Supposedly it was loaded with a powder that had a stabilizer for hot temperatures, i.e. the South Pacific. In the frigid Korean winter this stabilizer slowed the burn rate. Supposedly some it was tested in extreme cold and found to produce only about 800 fps, instead of the usual 1900.
          The other explanation I’ve heard is that those bullets found in the quilted jackets had gone through cover or ricocheted off rocks or frozen ground and lost velocity before hitting the target. Absent a controlled test, who knows the truth?

          • Don Ward

            That is a neat theory about the stabilizer.

            Although we have a happy story here at TFB from a couple days ago about that Navy Seal who was shot 27 times and kept on going. It shouldn’t be unreasonable that the “bad guys” were able to soak up shots and keep on going.

          • n0truscotsman

            I have heard of that, although Im unable to find any documentation to prove it. It is a very interesting theory.

            I’ve always just blamed missed shots for the “failure”.

            (and in case anybody didn’t catch my tone above, I was being sarcastic. And yes, that discussion turned into a pissing match here, which i watched in morbid curiosity)

          • Beaumont

            I’ve talked to a vet who was in one of those firefights. He summed it up thusly: “We were cold. We were shivering. We were hungry. We missed a lot.”

    • Crap! They’re catching on to my dastardly plan!

    • Marc

      Yes, .40x.99 Swedish.

    • Cymond

      Is that a bad thing? At this point, I come here more for the comments than the articles (although they do occasionally post something fantastic).

  • SD3

    Uh oh. It’s the 7.62x 39, isn’t it? The commies we’re right all along.

    • iksnilol

      While I like the x39 it could be improved. Maybe make the case longer and use a smaller, longer bullet?

      Something like 6.5x45mm. Would probably be a bit heavy. Though you could also just neck down 7.62×39 to 6.5 and use 140 grain bullets and get some long range performance.

      • That, uh, does not sound very competitive.

        • iksnilol

          Seriously?! Can it at least match 6.5 Grendel? I mean Grendel is essentially a x39 without the taper.

          • Depends how much longer you made it. But 140gr is very, very long and heavy for that bore and case. Velocity would be poor.

      • Guest

        You pretty much described the 6.5 Grendel, ‘cept the longer case. No need for the longer case though as the Grendel does nearly as good as a 7.62 x 51 as it is.

        • The Grendel is a bit of a Faustian bargain. You can’t get everything you want at once. This allows a fairly clever marketing campaign (loads optimized for energy retention are advertised as needed, as are loads with better external ballistics), but it means that any attempt to standardize a Grendel loading involves making hard compromises.

  • toms

    I think the chinese 5.8 dmr LR round is about as close to ideal as it gets, basically a 5.45 on steroids running at low pressure too. 6.8 is great in specII loads and is a good compromise round that I shoot a lot, grendel needs a longer barrel to shine, 260 6.5×47 ect are awesome but have too much weight/recoil for sensitive types and need longer pipes to utilize the powder capacity. Just an opinion. The new 556 loads like 855a1 are just too hot and are going to wear guns out quick never mind that 5.56 was designed around a very long barrel. Mk262 is good but I wouldn’t want to shoot it at bad guys in ceramic body armor.

    • 6.8 SPC Spec II produces much more bolt thrust and wear than M855A1 and has inferior ballistics. I don’t see it catching on.

      • iksnilol

        I don’t understand the hype regarding 6.8 SPC.

        The Chinese are onto something with the 5.8mm. They use it in sniper rifles, MGs and assault rifles (though a higher pressure loading for the former two).

        • It’s proven a little inadequate for long range stuff, but it’s hard to argue with the penetration of the DBP-10.

          • Uniform223

            As I understand it, the 6.8 Remmington SPC was design to offer the roughly same engagement ranges as a 5.56 out of an M4 but with superior ballistics within those ranges. Of course I maybe wrong, but what ever.

          • It was designed as an alternative to the early Mk. 262. At this point, it is exceeded in performance by the modern iteration of that cartridge. It produces an inferior trajectory due to a lower velocity and equal or lower ballistic coefficient.

            Consider, for example, that compared to 6.8 SPC loaded with a 115gr Sierra Match King, modern Mk. 262 produces 90% the energy or greater between 280 and 740 meters, while weighing three quarters as much.

          • toms

            Where are you getting these numbers? They don’t jive with any calculations I am familiar with. I shoot both but for example the wilson combat 110 grain load leaves a 16″ barrel at 2,700 and has superior energy at all ranges to Mk262. Comparing hot rod rounds is more appropriate as the Mk262 is a hot rod round.

          • Early Mk. 262 ran standard pressures and produced something like 2,640 ft/s from an 18″ barrel. Modern Mk. 262 runs 68,000 PSI (which it can get away with due to a temperature stable powder it shares with Mk. 318 and M855A1, and because of good quality control), and produces something like 2,800-2,850 ft/s from the same length barrel.

            Wilson Combat advertises their 110gr loads at 2,600 ft/s Hornady’s 110gr 6.8 V-Max runs something like 2,550 ft/s.

            Now, keep in mind that due to bolt thrust concerns, 6.8 SPC will run significantly lower pressures than 5.56mm (for a given level of bolt thrust, 6.8 SPC is allowed 79% as much pressure as 5.56mm). So, to square with Mk. 262’s 68 KPSI MAP, 6.8 SPC is allowed 53,700 PSI peak pressure… Which is pretty close to 6.8 SPC’s 55KPSI MAP. So by using normal 6.8 specs we’re actually erring on its side, not Mk. 262.

            According to ARFCOM’s 6.8 SPC tech info page, 6.8 SPC is capable of sending a 115gr bullet at 2,625 ft/s – I frankly think this is optimistic, but we’ll roll with it, anyway. That page also lists the BC of the 115gr Sierra Match King at .324 G1, which converts to .163 G7 using JBM’s drag function converter. There are bullets for the 6.8 SPC that have a higher BC but A.) The 115gr Sierra is the bullet it was designed for and B.) The same is true for heavy 5.56mm ball.

            So using JBM’s ballistic calculator, we put in Mk. 262’s value of 2,800 ft/s with a 77gr bullet and a .190 G7 BC (I’ve seen this verified by a number of sources, and it squares with a shape analysis, too. I keep a repository of BC figures here, it included). And then in another window we put in 6.8 SPC with a .163 G7 BC, 115gr bullet, and 2,625 ft/s MV.

            BTW, if you want to replicate this calculation, use a sight height of 2.6″, set energy readout to “Joules”, and use meters for range increments.

            What’s the result? Well, my original calculation was done a long time ago probably with slightly different figures, but it’s much the same regardless. According to the new data, Mk. 262 hits 90% the energy of 6.8 SPC at 290-300m, and doesn’t drop below that level until 720 meters. Between 400-630m, in fact, Mk. 262 possesses more raw energy than 6.8 SPC.

          • Toms

            The barnes 110 grain TSX was the wilson load I referred to at 2700 from a 16* pipe. Second part, equate both of those calculations from 14.5 inch barrels, which is what they would be flying out of. and the numbers get more telling. The gist of what I am saying is that people who shoot 6.8 a lot, handload ect. get a lot more out of the cartridge than what is published. When using SSA brass, modern powders from st marks, and longer COAL mags that get to 2.32 you are closer to comparing oranges to oranges. I think that building a whole new gun around the cartridge designed for a purpose is a better way to go in the long run instead of trying to supercharge existing cartridges and cram them into existing platforms. The 5.8 is an example of that. But in an ar15 with a 14.5 inch barrel I would choose the 6.8 over the 5.56 any day saying this as some one who has shot thousands of both rounds at living things. My 120 grain SST load goes 2585 at 2.32 oal from my custom DI Six8 16″ without signs of pressure or any other concerns. Just throwing it out there. If I have to shoot something past 600 yards I am not using a 6.8 or a 5.56 for that matter.

          • Hotrodding handloaders will almost always get way better than factory performance out of a cartridge. One of the several reasons for this is that high pressure signs may not occur until 75,000 PSI or higher pressure. It’s disingenuous to compare factory ammo to handloads, in the same way it would be if you compared a stock Mustang to one with a Coyote under the hood.

          • toms

            The Wilson combat 110 gr tsx tac load, which is actually not on sale right now, but was a couple of months ago IS a factory load. The pressure on it was measured by constructor on 6.8 forums and got no where near 75k pressure. I think it was 61K or so. The numbers don’t lie the 6.8 is not as “Ballistically inferior” as you claim. With half of the money big army threw at developing loads like 855a1 or 262 the 6.8 could see a huge performance gain and may be the best compromise available without significant platform changes. No doubt better packages could be designed but 6.8 is making a comeback. So many of the factory loads are loaded weak because of the Remington chamber fiasco early on especially those from hornady. Bottom line, it is an efficient cartridge that has significantly more powder capacity, significantly more energy at most if not all combat distances, performs well from shorter length barrels, and has a similar trajectory to 5.56.

          • Yes, it’s a factory load advertised as 110gr at 2,600 ft/s out of a 16″ barrel. Where are you getting this extra 100 ft/s from?

            A 6.8 SPC rifle running 61KPSI is probably unsafe with a standard AR-15 bolt. That is the equivalent of a 77,000 PSI 5.56mm cartridge.

            6.8 SPC is just not a very good cartridge. At least 6.5 Grendel was a good effort at meeting the wrong requirements; 6.8 has nothing going for it: Not velocity, not form factor, nothing.

          • Also, you are kidding yourself if you seriously think it has a similar trajectory to 5.56mm (which has almost the same BC and much better velocity). Maybe do some ballistic calculations and find out for yourself, eh?

          • n0truscotsman

            holy crap. I’ve had a small arms repairman from an ODA back in 2011 explain this to me about the 6.8 SPC, and in my infinite stupidity, I never took notes and picked for more information. Thanks for refreshing a point that I have long lost the specifics to.

      • toms

        2700 from a factory 110 load in a 16 inch barrel is plenty of power. Not true on the bolt thrust issue as this has been discussed many times on 6.8 forum by engineers who specialize in cartridge development and test pressure ect. Hot 6.8 loads come under the specs on M855A1, never powders have helped this problem. Barrel wear is also were the m855a1 looses ground. HK engineers among others have noted that the m855a1 is not a safe round as currently loaded especially when temps climb. 63,000+K is not safe in a spec M4. The new 6.8 pmags (what I use) allow for some serious improvements, with 130’s and it rivals the range of the grendel from a shorter barrel. The 6.8 got a bad rap early on due to remingtons mistakes. I still don’t think its the best round for the military but it is better than 5.56 imho especially in an unmoded AR.

        • I’m not sure how I should respond to this. 6.8mm produces more bolt thrust than 5.56 at a given pressure. That’s how bolt thrust works.

          M855A1 is a perfectly safe round. So is 6.8 SPC, but you can’t run it as hot as 5.56 in an M4. “Newer powders” don’t have anything to do with this, it’s just physics.

          The new 6.8mm PMags are not M4-compatible, and frankly, I don’t see a point in the whole exercise if you’re going to invent a completely new rifle, anyway.

          The 6.8mm is an entirely unremarkable cartridge, possessing low velocity, poor bullet form factor, and being heavier, wider, and hard on guns to boot.

          • Uniform223

            From my understanding and reading the of M855A1, its no free lunch. The US Army had to work within the constraints of the bullet, casing, and the platform it was to be primarily used in ( M4 and later the M4A1 ). In doing so the US Army reached their goal of a better performing all purpose round for the troops.
            There is no doubt that in order to increase the muzzle velocity out of a 14.5inch barrel they had to use a faster hotter burning powder to reach that goal. In doing so they have created a cartridge that is just as the very edge of what the M4A1 can mechanically handle. Also the whole, “it wears down the barrel faster” went right out the window as the US Army upgraded the M4 to the A1 version with a heavier and thicker barrel profile ( I suspect the EPR is the reason behind upgrade. Also an added benefit is that the new barrel profile offers less muzzle whip thus resulting in better accuracy ).

            It is worth mentioning that is has been 4 years since the US Army starting issuing the M855A1 to the troops. If increased wear on parts is a real concern, surely an incident of the sorts would have been mentioned by now.

          • M855A1 is not a free lunch. It is however, much better optimized for the M4, and incorporates a significant body of ballistics research that M855 does not, so I’d go ahead and say it’s a lot better than M855, or any conventional alternative cartridge, for that matter.

  • dave

    6,5 Creedmoor is pretty close to Ideal in my opinion.

    • It is very large. It’s difficult to imagine that weapons chambered for 6.5 Creedmore would enjoy any advantage over 7.62mm weapons in most instances, and it’s been thoroughly established that “full-caliber” rifle-armed infantry are at a serious disadvantage vs. ones armed with intermediate caliber rifles.

  • Lance

    If you wont goto a all 3006 set of arms then no theirs no universal caliber they’ll do the job. In my opinion 7.62×51 or 308 is the only caliber that be for a take in a post apocalyptic world. Can fight hostels and hunt with that caliber. .223/5.56mm and 5.45mm is nice but too small for most game. 7.62×39 is too small for game as well and is a inaccurate caliber.

    • 5.56mm will kill anything up to and including whitetail without problem.

      • Anonymoose

        Maybe in the South. Whitetails here are pretty darn big.

        • Whitetails in Northern New Mexico aren’t that small, either. There’s a prejudice against 5.56 for larger game that my experience doesn’t bear out. With proper bullet selection and shot placement, it is quite effective against medium sized game.

          Here’s a Georgian who’s had luck similar to mine with Mk. 318 against whitetail. I’ve never taken a buck with it, though.

          • Pilgrim Farmer

            Hey… Dats my video… I’ve actually shot 4 deer with the .223/5.56. As long as you wait for the deer to position itself perpendicular to your rifles bore axis, and hit something soft that contains blood, and use a modern expanding bullet, the deer will never know what hit it. These are things we should be doing anyways regardless of caliber.

            This deer season i’ll be using a BCM Recce with Federal Fusion 62gr MSR, and no reservations.

          • Great to have you commenting! I agree with you completely.

          • phale

            Doesn’t BEAR out? Hahaha…

          • Beaumont

            Yep. Shot placement rules. The 5.56 will take all the deer one can find to shoot at, if the hunter does his part.

            It’s also worth noting that the 5.56 is popular with hog hunters.

        • Aaron E

          There are some interesting 5.56mm/.223 caliber bullet selections, that if placed properly will definitely get the job done. In addition to the ballistic tips that can do well, DRT Ammo has a jacketed frangible round that has proven to be very deadly on large deer.

          http://www.drtammo.com/DRT-Technology


          Video shows the shot on the buck, and subsequent field dressing to show organ damage!

    • Dracon1201

      7.62×39 is not inaccurate. Current ammo is just cheap and inconsistently loaded. If you load them with as much care as your 5.56, it will be as accurate.

      • iksnilol

        7.62×39 is not inaccurate if you use decent ammo (not the cheapest but not expensive either) + use a decent barrel.

        + how can 7.62×39 be too small when it is the same caliber as .308? IMO from what I have seen 7.62×39 can be used for pretty much everything, even moose if you are careful and get close.

  • ColaBox

    .300BLK is as close as it gets, but lets be frank here, its not possible. Nobody can agree on what makes a good cartridge, and even if there was an agreement in the general scope, then you have arguments in the sub categories.

    • 5.56×45 enjoys about 140m overmatch space against comparable rifles chambered in .300 Blackout. Since the PEO Soldier Office considers having overmatch against 7.62x39mm armed enemies to be very important, I don’t think the .300 Blackout can be seriously considered as an infantry cartridge.

      • ColaBox

        I gotta disagree, the article you provided was excellent, however it does make note of the fact that though the 5.56 does have about a 100 yard advantage over the 7.62, it also takes into account the human factor, as well as the fact that most engagements don’t take place that far out. It has a lot of potential when you consider the 7.62×39 history alone. A .30 caliber compatible with the AR platform and high performance with a suppressor seems like a good choice, it can even be cost effective with you only needing to clip the brass.

        • Please tell me what is this “human factor” that gives 7.62 such an advantage over 5.56mm.

          You’re right; most engagements do not take place that far out, and in fact the use of effective rifle fire beyond 200m is extremely scarce. Because of this, I think one could get away with using the .300 Blackout (while annoying the PEO Soldier Office), though I’m not sure why one would want to, since it’s heavier and less effective than 5.56mm.

          There’s nothing magical about .30 caliber. Nothing.

          • ColaBox

            Human factor, at least in this case refers to ones ability to actually hit accurately. The biggest complain soldiers/people have about 5.56 is its lack of penetration with body armor, or its over penetration with soft targets. Iv heard and read articles from soldiers coming from Afghanistan stating that 5.56 would have little to hit due to the enemy’s low muscle and fat concentration, requiring multiple shots to bring down. Now a lot of it has been picked at until they declare it to be shot placement. However, 7.62 being a heaver bullet goes slower, but its increased size means it hits harder. Higher penetration against hard targets and higher trauma to soft targets due to the lower velocity, correct me if im wrong, but that’s the result iv seen from gel tests and ballistic charts. Heavier in what regard, carry wise or mass? Can you explain how its less effective in your opinion then 5.56?

          • I recommend you read a few articles on my blog. Virtually everything you’ve said here is dissonant with real data and the current understanding of ballistics.

          • Mark N.

            An article posted here suggests that the issue was the M185 round and its inconsistency in yawing after striking a target. Since yaw/tumbling is the major factor in the .223s ability to wound, this inconsistency resulted in widely disparate effectiveness of the round in combat. The M185A1 was designed to rectify this problem, and from what I’ve read, has done so quite well.

          • Correct, though I have one nit to pick: The designation is “M855”.

  • Anonymoose

    No one said 7mm-08? Really? It’s perfect for reaching out there and “touching” people with plenty of power, and all it requires is a simple barrel swap to change from 7.62×51/.308.

    • I don’t see how it’s materially different than 7.62x51mm.

      • Paladin

        Better BC, it retains velocity further than .308

        • Yes, it does, but the advantage is pretty minor, to be honest. I mean, I agree it’s technically better than the 7.62mm, but it’s almost the exact same cartridge, so I feel one might as well argue .30 T/C is the superior round.

  • James Kachman

    .280 British, hands down.

    Oh, what’s that?

    Yeah, it’s pretty underground.
    *adjusts glasses*
    You’ve probably never heard of it.

    • .280 or .280/30?

      Doesn’t matter; either one isn’t any different than 7.62. >:)

      • James Kachman

        .280/30, since it’s the one that had the closest bet. Suddler, you ignorant jackwagon…..

        • James Kachman

          *Studler. I cannot spell.

        • However enthusiastic the Brits were about the “two eight oh”, I don’t really see the attraction. It’s not really any more suitable for light automatic rifles than 7.62mm, and it doesn’t provide a ballistic advantage over it, either.

          • iksnilol

            Isn’t it lighter and less affected by wind?

            .280 brit is similar to .260 Remington, right?

          • Mostly, the trajectory is pretty uninspiring and it’s not much lighter.

          • James Kachman

            As far as I recall, it had a lighter recoil and lower weight per cartridge than the 7.62×51, both of which are common complaints about the 7.62 round. That being said, the FAL in 7.62 went on to prolific success. I’d be very interested to see if the Rhodesian Fireforce concept would work as well with the troopies using a lighter round; although the majority of causalities were caused by air assets, supposedly the greater penetrative power of the 7.62x51mm was useful in the bush.

          • Yes, it did, though not by as much as is often claimed. .280/30 is much closer in weight to 7.62×51 than it is to 5.56mm, for instance, which makes sense because it uses the same case head and almost has the same bullet weight as the former cartridge.

            If the .280 British had been adopted, I certainly wouldn’t be complaining right now about the missed opportunity that was the T65 Light Rifle cartridge, but at this point its time is well past.

    • Beaumont

      And for handguns, .475 Achilles.

      What? You’re not familiar with it? *strokes beard*

      • Isn’t that supposed to be .480 Achilles?

        • iksnilol

          Pfft, .224 Boz is way better.

      • Blake

        Methinks heeled bullet production couldn’t keep up with the demand…

  • joshv06

    I still think that there is a void to be filled. In my eyes, an ultimate cartridge needs:

    High BC
    Good taper for extraction (more than the .223 taper, less than x39)
    Not too high pressure
    Fast powder burn – Bigger bore diameter helps
    Low cost to make
    Flat trajectory
    Tumble ability (or not, depending on POU)

    I think the ultimate cartridge will use a .223 casing due to all the parts in use. I think it will be something along the lines of a 6.5/6.8 wildcat round.

  • TFB Reader

    “From historical observations, most encounters happen at 100m or less. The ammunition expenditure per casualty ratio for these conflicts is usually hundreds or thousands to one.”

    Are we debating the right question?

    • That squares pretty well with my premises, actually.

    • wetcorps

      This.
      Which small arms and calibers you use isn’t as relevant as we like to think just because small arms are our hobby.
      You can’t fight a war without “boots on the ground”, but most of the killing will be done with explosives, artillery and planes.

  • Blake

    lol: “reducing “unknown unknowns” perhaps to “known unknowns””

  • Blake

    From yesterday: 6.5×55 Swede, by virtue of incumbency 🙂

  • Grindstone50k

    F*ck it. 11x60mm Mauser is the best!

    • iksnilol

      14.5x114mm is best!

      Now to make a rifle that weighs less than 20kg for it.

  • The ultimate rifle? I dunno… I’m tied between the M41A Pulse Rifle and the Westinghouse M95A1 Phased Plasma Rifle.

    But the 9.2mm Podbyrin pistol is still the most powerful handgun in the world. 😉

    • iksnilol

      I don’t think that laser or plasma weapons are the future. Hear me out, bullets kill by causing bleeding and tearing stuff up and breaking bones (usually by bullets fragmenting or yawing). While laser or plasma weapons would cauterize the wound and shoot trough without tearing something up.

      • Hanover Fiste

        Actually, the rapid vaporisation of the material the directed energy beam hits acts like an explosive. Sorta like you hit the target with a stick of dynamite. Of course “stick of dynamite” is a turn of phrase, but with sufficient energy density, DE weapons can be devastating. However, I think we are a loooong way off from such weapons being fielded by infantry.

        • iksnilol

          Wouldn’t that require even more energy than just getting the ray to pierce the target?

  • Hanover Fiste

    With the maturation of 3D printing moving along may I humbly suggest:

    Every infantryman should carry a custom gun made to shoot bullets cast from molds of his own teeth.

  • DetroitMan

    It depends on what you want your rifle / cartridge system to do. Currently there is a cult of thinking that the system needs to be as light and handy as possible while offering the largest possible ammunition load out. It’s rooted in the idea that troops will expend most of their ammunition on suppressing fire or otherwise missing their targets, while artillery, airstrikes, and other heavy weapons will do most of the killing. To achieve that we have opted for the M4 / 5.56mm system, which is limited to 200 meters and has questionable stopping power. In short, the system is not an “all around” system. It is optimized for CQB and fire suppression, at the cost of range and stopping power. The Army has chosen this compromise and seems satisfied with it. The Marines have mostly followed suit (while keeping their M16’s), as have special forces. As long as the operational requirements remain the same, it’s doubtful that a better cartridge will be found. The 5.56mm is very well suited to these requirements.

    A true all around system would require a compromise between the desire for light weight and short weapon length against the reality that extending range and increasing stopping power require a larger caliber, which likely means a longer, heavier weapon as well. (A bullpup configuration could mitigate the weapon length and weight increase.) As many have said here, something in the 6.5mm range seems optimal for a cartridge that is asked to do everything on the modern battlefield. 6.5mm sits at the intersection of high ballistic coefficient and penetration capability with moderate projectile weights. Unfortunately, to truly make use of these capabilities, you need more cartridge length than the AR-15 platform will accommodate. The weight of the ammunition will also increase. In any case, it all comes back to what the Army decides it wants the capabilities of the standard infantryman to be. If they want them to be able to deliver effective fire at 400 meters or more, then we need a more capable cartridge. If they are content to limit them to 200 meters and let Designated Marksmen with specialized rifles handle the longer range work, then there is little reason to change from the current 5.56mm / 7.62mm combination that we field today.

    • What limits the 5.56mm/M4 system to 200m? Certainly not its trajectory of accuracy, according to my experience.

      • Uniform223

        Agreed. When I was younger and in the service we zeroed our weapons out to 300 meters and during the qualification we had to engage targets at 300 meters. My buddy who was a Marine ( I don’t hold that against him 😀 ) always bragged how he had to qualify at 500 meters. So obviously the platform is capable at engaging at ranges further then popular myth says. Though it should be said that those ranges are pretty much determined by how good and proficient the user is.

        I am tired of hearing and reading people saying that the military has handicapped its soldiers and marines by giving us “ineffective” rounds and weapons. I guarantee that a PORTION of people who always makes those remarks have either not served in the suck or just stuck in the old thinking of, “its a full rifle caliber or nothing!”.

        • I’ve been able to push my 6920 to 900m before I really started to struggle. It doesn’t have much gas out that far, but it’s still lethal.

      • DetroitMan

        “Limit” is too strong a word, but I used it for lack of a better one. The ability to hit the target and the ability to incapacitate the target are two different things. Once the 5.56mm round drops below 2700 FPS, it will not tumble or fragment reliably on impact. When launched from a 14 inch barrel, it drops below that threshold somewhere beyond 200 meters, but before 300 meters. There is also the issue of the projectile’s ability to deal with wind, brush, and barriers. Larger projectiles are provably better at defeating these and reaching the target.

        Stopping power is most certainly not a myth. Ask any hunter. Look at police studies of which handgun rounds are most effective. Look at Black Hawk Down. Ask the Army why they found it necessary to bring back 7.62mm rifles for limited issue in the infantry. Check the Army’s own study of battlefield wounds in Iraq. The fact is that the 5.56mm round provides the minimum wounding ability needed to take out a human target. It is also proven that its wounding power is greatly decreased once the bullet will no longer tumble and fragment.

        I think the better statement that I made is that the 5.56mm is optimized for fire suppression and CQB. It performs adequately in these roles and allows them to maximize the amount of ammunition carried for the weight. They have prioritized this over the better long range capabilities of a larger round. The Army has accepted the compromise of the 5.56mm in a carbine length barrel on the theory that infantry will seldom engage with their rifles beyond 200 meters. The Marines have opted for slightly longer range by sticking with a rifle length barrel. Both continue to deploy 7.62mm rifles in limited numbers to deal with targets at long range, behind barriers, etc. I’m not knocking the 5.56mm or M4, per se. They are adequate for the role assigned to them. However, they are not a true “all around” cartridge and rifle. If they were, there would be no need for the 7.62mm rifles and machine guns that we continue to deploy.

        • 1. Spitzer bullets are inherently unstable, and tumble at all velocities when they hit tissue. I do not know where this rumor that it does not tumble under 2700 ft/s comes from, but it’s not true.
          2. “Fragmentation” is often portrayed as being either nonexistent or catastrophic. The reality is that fragmentation increases in severity with velocity. M855 begins to fragment at about 2,100 ft/s, with fragmentation becoming most severe over 2,800 ft/s.

          3. M855 from an M4 Carbine produces around 1,000 J at 200m, which is more than an 8″ .44 Magnum revolver at the muzzle. The buck taken in that video I linked above would contest your idea that 5.56mm is at “the edge of its lethality” at 200m.

          4. Stopping power is a term that’s all but meaningless, because it attempts to distill a complex and nuanced subject into a linear scale. The truth is that any discussion of “stopping power” that relies on absolute statements such as “5.56mm is ineffective past 200m” is a poor one.

          I explore these topics in greater detail in the following posts:

          • DetroitMan

            I concede that I may have been wrong in some of the details about the wounding and fragmentation characteristics of the 5.56. However, the fact remains that fragmentation is the primary wounding mechanism of the round, and the severity of the fragmentation decreases proportional to velocity. The fact also remains that the 5.56 is poor at barrier penetration. It is also poor at resisting wind drift and cutting through brush to reach its target. If we are talking about a universal cartridge to serve all roles in long arms and machine guns – which is what I believe the linked PowerPoint presentation in the article was talking about – then the 5.56 clearly cannot fill that role. So my basic points remain:

            1) The 5.56 and M4 are optimized for CQB and fire suppression. The Army freely admits this. They believe engagement ranges will be relatively short and have elected to trade real long range capability for lighter weight, greater ammo load out, and less recoil.

            2) The Army believes that the 5.56 and M4 are inadequate for long range engagements. They rushed 7.62 rifles to Iraq and Afghanistan when it became clear that the enemy was going to consistently engage our troops from beyond what the Army considers to be the effective range of the 5.56/M4 system. They have never given up the 7.62 for sniper rifles or machine guns.

            3) A cartridge that can remove the need for the 7.62 must be larger than the 5.56. You can’t fit a gallon in a pint pot. Even with all the advances in bullet technology, you can’t make a 72 grain projectile penetrate barriers or resist wind as well as a 168 grain projectile. A larger projectile simply has more energy, at all ranges, when launched at comparable velocity.

            4) For all of these reasons, the 5.56 is not an “all around” cartridge. It is optimized to the needs of the Infantry, as their role is defined at present. It is inadequate for the needs of snipers and machine guns. The Army has further found a need to deploy designated marksmen with the infantry. The DM carries a 7.62 rifle for longer range and barrier penetration so that the infantry are not lacking these capabilities.

          • DetroitMan

            Addendum: I read your blog posts. Clearly you have done extensive research on the subject. I found your discussions on the design of a general purpose caliber to be very interesting. On the capabilities of the 5.56, I remain unconvinced. You cite studies that show its wounding properties are satisfactory. Other studies I have seen say it is not. Where I will agree with you is that as long as we continue to define the role of the infantry as we do today, there probably is not a better cartridge. The 5.56 is pretty much unbeatable in the weight category. If the infantry’s main need is to provide maximum volume of fire for suppression, then weight of ammo is the primary consideration. We can’t seriously consider adopting a general purpose caliber unless we are willing to challenge some of our assumptions about what the infantry need from their rifles, or how the weight in their combat load is allocated.

          • Uniform223

            M855A1 EPR, remedied a majority of the inefficiencies found in the original M855. If you are to look up the M855A1 EPR do NOT look up or read the article on the guns & ammo. That article was very premature and not well researched IMO and has unfortunately its disingenuous remarks spread like wild fire leading many to believe it before anything could really be said or researched to the contrary. It should be noted that the M855A1 is no free lunch though. Also in 4 years after adoption, there have been no recorded or publicly released incidents about excessive wear and catastrophic failures regarding the EPR.

          • Thank you. I’ve been railing against that article basically since it came out.

          • DetroitMan

            I wasn’t impressed by that Guns & Ammo article either.

          • Cite your studies, then. I cite mine.

          • DetroitMan

            I can’t. I read a lot over the years, but I don’t keep a list of links.

          • DetroitMan

            Ok, here is a new article that was posted recently. I admit it’s not a scientific study, but I take battlefield accounts seriously. The fact that this author is a medic who examined the wounds in detail lends weight, in my opinion. Some in the comments rightly point out that there is bias since a doctor only sees surviving victims. However, his medical opinion of the severity of 5.56 wounds verses 7.62 wounds makes a point. I would say this reinforces the notion that larger rounds are better at putting a target out of action.

            http://www.thetruthaboutguns.com/2014/10/daniel-zimmerman/medics-advice-shoot-heaviest-rifle-round-shoot-can-hit-shoot/

          • “Poor at barrier penetration” is far too general a statement. Yes, 5.56mm leaves something to be desired when used against some barriers. Those barriers typically also pose a significant obstacle to other small arms calibers as well. Is 5.56mm ideal in this respect? No, but I challenge you to find me one that is, while retaining all the positive characteristics of that caliber.

            5.56mm could be a general purpose cartridge, sort-of-kind-of, if you squint. However, the military has 7.62mm, so that point is moot.

            It’s misleading to say that 5.56mm is optimized for CQB, since by “CQB” you mean “a very generous definition of ‘the normal rifleman’s effective range'”. However, yes, 5.56mm is clearly not optimized as a kilometer cartridge.

            What do you mean by “real long range capability”? That capability exists (or doesn’t) in the soldier, not the round he’s shooting. Once it’s demonstrated to me that our soldiers are routinely effective against point targets to beyond 200m, I’ll start thinking about what sorts of rifle rounds would be best suited to 500m+ combat (5.56mm being explicitly designed for half-kilometer use; it’s in the original Air Force penetration requirement that gave birth to the .222 Remington Special, subsequently redesignated .223 Remington).

            2). Rifles are inadequate for long range engagements. The Army’s solution to this has been to issue Carl Gustav recoilless rifles, which I think is a far better solution than any GPC.

            3). Yes, but why bother with a GPC at all? What’s the need, especially when 7.62mm exists almost entirely in either belted or special ball form?

            4). The PEO Soldier Office disagrees (linked previously in one of my infodumps). They consider M855A1 to be a general purpose cartridge, explicitly. The only reason they don’t replace 7.62mm with it is because they’re getting even better capability out of that cartridge using the same technology in M80A1.

          • DetroitMan

            ” Is 5.56mm ideal in this respect? No, but I challenge you to find me one that is, while retaining all the positive characteristics of that caliber.”

            Can’t be done. If your position is that all of the positive characteristics of the 5.56 must be maintained in any replacement cartridge, then there is no reason to replace the 5.56. If we are going to seriously consider adopting a general purpose cartridge, then we have to be able to challenge our assumptions about what capabilities our troops need. Selecting different cartridges always involves trade offs, whether we are talking military, law enforcement, hunting, or target shooting. If you think that the 5.56’s characteristics are exactly what our troops need, then there is no room to discuss a replacement.

            “It’s misleading to say that 5.56mm is optimized for CQB, since by “CQB” you mean “a very generous definition of ‘the normal rifleman’s effective range'”.”

            Most of the praise / justification I hear for the 5.56/M4 is centered on its performance at close quarters. Iraq / Afghanistan involved a lot of door kicking and transport inside armored vehicles. A short, light weapon is ideal for those situations. As for the cartridge, there is a very real link between velocity and wounding, and therefore range. Yes, I am using a generous definition. Let’s face it though: the other big justification I hear of the 5.56 is the ease of controlling it in rapid fire. We don’t really use full auto outside of CQB, except to suppress. If you’re suppressing, a little muzzle climb isn’t going to defeat the purpose.

            “What do you mean by “real long range capability”? That capability exists (or doesn’t) in the soldier, not the round he’s shooting.”
            I agree that the capability exists within the soldier, or doesn’t. However, the cartridge and rifle support that capability, or they don’t. Snipers don’t use the 5.56 for a reason. It doesn’t resist the wind well. It is also easily deflected by obstacles as minor as tall grass. These things make a huge difference at 1 km, but they also make a difference at 500 meters. With a heavier projectile, the shooter does not have to adjust their point of aim as much to compensate for wind, so it’s easier to make the shot. There is also the issue of remaining energy and wounding properties as range increases. Now, as you have pointed out, the 5.56 is capable of reaching out to those ranges. Bigger cartridges do it better. Again, this goes back to a discussion of tradeoffs and assumptions of what our soldiers need.

    • n0truscotsman

      “It is optimized for CQB and fire suppression, at the cost of range and stopping power.”

      The M4 is capable of hitting human sized targets at 500 meters, and arguably, 700 meters with the proper ammunition (although in combat conditions such long ranged shots are very unlikely to impossible), so the M4 doesn’t compromise with range like many think it does.

      As far as “stopping power” goes, ignoring the obsolescence of that term, 5.56 produces similar to 44 magnum levels of muzzle energy given similar length of barrel (comparing apples to apples the best you can). Nobody in their right mind whines about the “stopping power” of 44 unless they’re 500S&W fans. 😉

      • DetroitMan

        Muzzle energy is meaningless in this discussion because we are not talking about shooting something at point blank range. The farther a bullet travels, the more energy it loses. Heavier bullets retain more energy at range. A 55 grain round from the .223 leaves the muzzle with 1282 ft-lbs of energy, but only has 581 ft-lbs remaining at 300 yards. A 150 grain round from the .308 leaves the muzzle with 2648 ft-lbs of energy, and has 1193 ft-lbs remaining at 300 yards.

        • n0truscotsman

          Muzzle energy is NOT meaningless by any stretch of the imagination, nor is it the decisive primary means to measure cartridge effectiveness.

          And yet you are comparing muzzle energies to try and argue favorable towards 7.62 vs 5.56, even though it is an apples and walnuts comparison…curious.

          My point is that nobody whines about 44 magnum’s “stopping power”, but will whine (its usually the same people) that 5.56 is lacking in that department. It makes no logical sense whatsoever.

          That was my point. 7.62 is great for machine guns and sniper rifles for very good reasons. Those reasons make it mediocre, if not undesirable outright, for general infantry rifle calibers.

          • DetroitMan

            Actually, I was comparing the remaining energy at 300 yards for both cartridges, because my original post was largely a discussion of long range capabilities. You seem to have missed that point. I don’t question the capability of the 5.56 to kill within its intended engagement range.

            The point of my original post is that a true all around cartridge needs to be able to do everything that we ask of long arms and machine guns. The 5.56 is not good at long range or barrier penetration, which is why we continue to deploy 7.62 platforms. If we want one cartridge to do all jobs, then we need to find a compromise between the 5.56 and the 7.62. One cartridge to do all jobs is a very tall order and it may not be possible to develop one. But our choices are either to try or to keep our current system of two cartridges. If we decide to try, then we will have decide which capabilities of the two cartridges we are willing to compromise on, because it is likely impossible to develop a cartridge that has 100% of the capabilities of both.

          • n0truscotsman

            I understand now, and your argument is fair.
            Im just skeptical of multi-purpose ANYTHING, to include cartridges and I used to be a proponent of such a thing.

          • I don’t think it would be a tragedy if what we had now was replaced by a GPC. GPC advocates would just sit back in their chairs feeling very smug, and our infantry would become slightly less effective. And, of course, pork would be doled out.

          • What more good can come of a cartridge that exceeds the capabilities of its users?

            How many requirements shall we lay at the feet of each cartridge design and why? What makes sense? I argue that it makes sense to delineate cartridges along production and logistical lines, and since military 7.62mm exists almost exclusively in belted and special ball form, why try to unify it with a cartridge that mostly comes on stripper clips? I do not see the sense in this; it seems like giving up the best aspects of each cartridge for some sort of theoretical advantage that doesn’t really bear out, an argument which itself neglects the cost of a caliber change-over!

          • DetroitMan

            The advantage to a general purpose cartridge is in logistics. Theoretically, if you could supply every long arm and machine gun with the same cartridge, your manufacturing and supply line are simplified. It has been said that is logistics that ultimately win wars. The question is whether the logistical advantage is worth it. We would have to trade two cartridges that are adapted to different needs for a single one. The new single cartridge would likely not fulfill the role of the 5.56 or the 7.62 completely. Most likely the big sacrifice would fall on the infantry, since the new cartridge would need to be larger than 5.56. They would either have to accept less ammo load out, carry more weight, or find other ways to save weight in their gear. However, they would also get increased range and barrier penetration. Of course they would have to be trained to take advantage of those. All of this would cost us. So the ultimate question is whether the end result is worth the price of admission. The military spends billions on weapons programs every year. We have the money, it’s just a question of what we spend it on. If a new cartridge was judged worthwhile, we could afford it.

          • The GPC crowd has yet to explain to me how a cartridge that is heavier and bulkier than the by-far most-used ammunition in the US military, which it would theoretically replace, is better for logistics.

          • DetroitMan

            According to theory, there are two advantages. First you only have to manufacture one cartridge. All of your ammunition plants can just crank out one round. The second is that everyone’s weapon can use the same ammo, so you reduce the chance for errors in supply or one weapon system having insufficient ammo on hand. You take what you have and load it into rifle magazines or belt links. Obviously there will be some nuance. For example, it’s likely that there will be one load tailored for rifles and another for machine guns. In a pinch, one weapon can use the other’s tailored ammo with a marginal reduction in effectiveness. Of course the theory needs to be subjected to some studies and tests to see if the advantages are real and worthwhile.

          • 1. GPC advocates like to make it seem like the split between 5.56 and 7.62 is about 50/50; it’s not, it’s far more lopsided towards 5.56. Sacrificing the characteristics of the much much more common round to achieve commonality with a much less common round seems silly to me.

            2. Everyone’s weapon CANNOT use the same ammunition under a GPC scheme. Today we have three basic kinds of small arms ammunition, 5.56mm loose (on clips), 5.56mm belted, and 7.62mm belted. Under the GPC scheme, you’d have GPC loose and GPC belted. Given that it’s not really lighter to issue a GPC than to replace M249s with 7.62mm machine guns – which would result in having two basic kinds of ammunition as well, 5.56mm loose and 7.62mm belted – I don’t really see the point.

  • Y-man

    Must have missed it, but what does DTIC mean?

    • Y-Man, good to have you commenting. “DTIC” is the Defense Technical Information Center, a repository of military technology documents.

      • Y-man

        Many thanks Nathaniel F.! I will definitely follow the DTIC series more going forward…

        • Absolutely no problem at all, Y-Man, it’s good to have you on!

  • Diver6106

    THAT is a firearm with multiple barrels/ part kits for changing out rounds in the same weapon.

  • john huscio

    .300 blackout. Yes, everybodys head over heels about its suppressed performance, but it could be a hell of an all around caliber as well if its use becomes more widespread…

    • As I mentioned elsewhere in these comments, the 5.56×45 enjoys a 140m overmatch distance versus the .300 AAC Blackout, so the latter is unlikely to catch on outside of specialized roles.

  • JSmath

    Fantastic article, Nathaniel. Thank you for sharing/writing the various parts of it.

    I can imagine, but am curious with your particularly high expertise, what do you think of adopting a 5.7mm-like cartridge for use in pistols and SMGs (, PDWs, Carbines), then floating the 5.56mm replacement cartridge to a larger diameter, something closer towards 7.62mm (7mm)?

    • For all but personal defense weapons, 5.7mm really doesn’t meet the requirements. I think 5.56mm is a very good infantry rifle cartridge, and 7.62mm is pretty good but not perfect.

      People love to chase caliber, there’s a whole industry based on convincing people that they need a whole new gun in a hot new caliber. In reality, 5.56mm is very good and 7.62mm bridges the gap between it and .50 neatly. Breaking the caliber demarcations along different lines doesn’t make a lot of sense to me.

  • ChaosbreedX

    http://www.quarryhs.co.uk/miltech.htm
    Scroll down for articles. Most authoritative I’ve read on the net.

  • Giolli Joker
  • gunslinger

    wait
    those rounds from the guns out of judge dread seem to be the “ultimate round”

    you can fire exactly what you want with each shot

  • supergun

    I would take the 308 all day long.

  • Spork Star

    ** General Purpose Rounds – I can give ya an excellent round but you’re not going to like what it does to your magazine capacity. The 6.5mm Grendel. But youll need a custom slug type for it tailored for military use – armor piercing boat tail which tumbles on impact (like the 7N6). That IS The Perfect combination. Anything else is going to compromise mass, velocity, or diameter, which translates to dampened performance or stopping power. The only hit that 6.5mmG takes is on magazine capacity (but NOT bullet weight).

    With a 40 round PMAG you’re still going to get 30 rounds comfortably seated anyway, and curved magazines can be made which U-bend, and even a small bend (J shaped) is going to save enough vertical space to make it comfortable. As for magazine capacity you have to go up to 40-60 rounds to keep up with the Chinese and Russians (all of their magazines are going to casket quad stack mags with 50 or 60 capacity, and they dont malfunction like these half baked Surefire magazines do).

    The 6.5mm caliber size and the length of the slug allows it to be tricked out to the point where it will outperform a standard .308 in every category (though a tricked out .308 would still be a little better).

    ** Handgun Rounds – Large brass case such as a .50 AE, high pressure (30-40Kpsi), necked down to 9mm and shortened (I suggest 28mm so shave off 7mm). Use a heavier spring and put a mandatory muzzlebreak on the gun to maintain it long term. Using a long, heavy armor piercing slug similar to the VSS round (~250 grain) its going to hit like a .44mag and being a 9mm armor piercer its going to blast through armor better than a .223. More effective length economy on the pistol bullets means its going to be easier to hold, for it being a hand cannon.

    But your pistol will only hold 8 rounds. . . maybe 6 for a compact version. But seriously, how many shots does a last ditch “omg” weapon really need to have? The whole point of a soldier carrying a pistol is portable utility, and backup, and thats it. The M1911 served over 70 years and its only got 7 or 8 shots. If 6 or 8 shots isnt good enough for you then that’s why they should all be carrying 2 extra magazines. And point of fact, this is a hell of alot more effective than a .45acp for the same size gun as an M1911.

    ** Intermediate Rounds – General Dynamics has this nailed with their .338 Norma Magnum medium machinegun design. The bullets weigh more to carry but its so accurate you need alot less of them, and its even more accurate out at extreme range than an M2 (.50) because of lighter recoil. And an 8.6mm rifle round is no laughing matter no matter what range youre at.