6x45mm makes a comeback

The 6x45mm SAW was an experimental round developed by the US Army in the 1970s.

Black Hills ammunition will be selling 6x45mm ammunition next month. Why is it being resurrected? It can be used in an AR-15 with no other changes than a new barrel and the round gives better ballistic performance than the 5.56mm NATO.

It uses standard .243 bullets (85 and 100 grain with 115 grain AP round being developed).

Sporting Products LLC will be distributing a range of uppers and compete rifles chambered in 6x45mm.

Pricing for the ammunition is not yet decided, but I was told it will cost around the same as match grade 5.56x45mm.

UPDATE: Commenters have pointed out that it cannot be the same case as the original 6x45mm SAW. They were not giving out ballistic info so I don’t know if it matches the original ballistic performance of the SAW. They certainty mentioned the SAW when I was talking with them.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Mouse

    Huh, I have never heard of this round… How is that I wonder? Oh well, looks like another round built by the highest bidder. 😐

  • Is anything known about the terminal ballistics? This is a new one to me too.

    The .243 is a deer round but not sure how this compares to it in terms of power. To fit the AR platform it’s going to have to lose some length so there’s going to be some drop off in performance.

    Looks like another attempt to fill the power gap between 5.56mm and 7.62 NATO. Interesting to see how it stacks up against the 6.5 Grendel and 6.8 SPC.

    Keep up the great work Steve!

    • Jay-Mac, I asked them about power. It is an intermediate cartridge, more powerful than the 5.56mm, but not in the same league as the .243 Win.

  • Vak

    How does it compare to, let’s say… 6.8MPC or 6.5 grendel ?

    • Vak, they did not have specs for me. When they are published I will blog.

  • R.A.W.

    I don’t think this is the same 6x45mm as the experimental SAW cartridge. Take a gander:


    The 6x45mm SAW had a significantly greater OAL than the 5.56 NATO and a larger case head too as per the wikipedia specs. IIRC the aluminum-cased version was larger still.

    I think this is just a 5.56×45 NATO necked up to 6mm.

    • R.A.W., I get that impression. They did not have specs, so hard to say if performance between this 6×45 and the 6mm SAW differs.

  • Bill Lester

    Nothing to see here folks. The 6mm SAW wasn’t a big enough ballistic jump from 5.56mm in the 70’s and is no more so today. It is a very accurate round however. (But so too is 5.56/.223.)

  • High Standard out of Houston has been selling 6x45mm ammo and uppers for a few years now.

  • The 6×45 and the 6×47 (built on the 222 Magnum) have been around for a long time. How, though, is this diferent from the 6.8 SPC or the 6.5 Grendel or whatever?

    Yes, this does look like yet another bureaucratic exercise.

  • Cat

    Actually it’s a .223 necked up to 6mm. Same bolt, same magazines, just a new barrel and you’re done.

  • Zach

    To me this looks VERY interesting and appealing. We know Black Hills can produce both quality and quantity, which is important, and one can try out this round with nothing but a barrel change (though for most of us a complete upper will be easier). I assume the same mags work? I would like to know ballistics. This sounds a lot more appealing than 6.5G and somewhat more appealing than 6.8 SPC in terms of practicality and cost of ownership.

  • Meltron

    hey does anyone know what kind of sights are on that AR?

  • R.A.W.

    Steve, the original 6x45mm SAW cartridge used really heavy bullets going not that quickly (105 grain @ 2400 FPS). This probably has to use lighter bullets because of overall length concerns re: ar15 receiver length. 6mm SAW was not loaded to particularly high pressures either IIRC, so this cartridge probably comes close in terms of overall power. I wouldn’t be surprised if it beats it for velocity at least.

    Interesting that they mentioned the SAW!

  • Vak

    @ Meltron :

    looks like aimpoint stuff to me.

  • How about bringing the .280 british back?

  • Bill Lester

    Re. Ballistics:

    Hodgdon’s handloading data derived from a 24″ test barrel (a lot longer than any “serious” AR) shows 60-grain bullets maxing out at 3160 fps, 70’s at 3066 fps, 75’s at 2952 fps, 80’s at 2904 fps, and 85’s at 2818 fps. I believe anything heavier won’t feed through the magazines, so I’m sure the interest in those is limited.

  • Whatever

    I am leery of owning firearms that use very similar yet incompatible ammunition.

    I was wondering why after WW2 that the US military didn’t adopt a cartridge that was about 20-30% more powerful than the 7.62x39mm cartridge. They must have known about it or had a good guess at its performance. Like with artillery, you just have to be able to shoot farther than your enemy.

    If it wasn’t a Japanese cartridge, the military might have taken notice of the 6.5x50mm Arisaka cartridge and saw that it was close to ideal for a military cartridge (except for the semi-rim on it).

  • Max

    Looks good to me, I think the 6.8 is too wide for the goals they had for it, they should have gone with at most a 6.5 and probably best would have been a 6mm to keep BC higher and velocity high as well. Super stubby bullets at low velocities for a rifle don’t really strike me as the best way to increase performance. Accept a slightly narrower bullet and don’t have to lose out on those things.

  • Larry

    Meltron –
    Looks like a compM4 aimpoint with a magnifier (the same flip magnifier that usually accompanies an eotech).

  • Vitor

    Well, 110 grain 6mm will have considerably better ballistics than a 110 grain 6.8mm, since it’s much slender.

  • Meltron

    @ Vak & Larry

    Thanks a lot playas, I thought they looked like Swedish glass, but the red dot looked alittle bigger then the Comp M2

  • I’ve got an AR I built in 6 x 45 as a dedicated predator hunting rifle. It’s a great caliber, as is the 6 x 47, and puts coyotes down with authority. Very interesting to hear commerial ammunition will be available for it!

  • Nathaniel

    This is not 6x45mm SAW. That was a steel cased round of 63.5mm OAL and 10.8mm case head designed for the M249 in the 70s, but having three rounds in the supply chain didn’t sit well with the military.

    6mm-.223, which is what this is, was probably the first .223 wildcat ever made.

    While they replicate the energy of the 6x45mm fairly well with this load, they can’t possibly match the awesome ballistic coefficient of the 6mm SAW’s bullet. It was something ridiculous, like .62, IIRC. The tracers also burned for some ridiculous distance, like 1200 yards.

  • Nathaniel

    Oops! You guys caught it already!
    The 6x45mm SAW shot a 105 grain streamlined bullet at 2520fps, but it was designed for low pressure. While the 6mm-.223 loadings shown here match that at the muzzle, it’s likely they fall much quicker than the bullets used in the SAW round.
    Tony Williams, a notable firearms expert, cites that the 6x45mm SAW was still producing 250 ft-lbs at 1000 yards; this figure is would put its BC in the range of .405, which is the BC of the Hornady JSPs I suspect those 6mm-.223s are using. Hornady’s reloading guide suggests that the 6mm-.223 is perfectly capable of 2550 fps in that bullet weight. However, I suspect Tony’s estimate is a bit more conservative than it should be, since the bullets for the 6mm-.223 are much shorter and less aerodynamic than those used for the 6x45mm SAW. I remember figures for the SAW’s BC in the .55 range, though it’s certainly possible I am mistaken.

  • iMick

    I’ve always wondered why they haven’t just necked the 5.56×45 up to 6mm/.243 projectiles as a better platform than the standard 5.56. Maybe it’s to obvious a solution. Won’t match 6.5 or 6.8 levels but will be close and only requires a barrel so for me is the better compromise.

  • Brian

    The 6×45 (6mm-.223) is NOT the same thing as the 6mm SAW; not even close, in fact. Black Hills is going to be making the 6mm-.223, not the experimental military cartridge.

  • I just checked Midway USA and they didn’t have this ammunition listed yet. Has anyone seen it for sale yet?

  • Gary

    I’ve owned a 6×45 since 1991…Stoner should have had Sierra or Hornady help him understand ballistics a little more and the grievous mistake called a 5.56 would have been avoided…The 6×45 is a great cartridge and you slide up the BC scale quite a bit with .244 bullets…It surpasses the 5.56 ballistics by a third maybe more…An 85-90 gr bullet make a big difference when conditions are working against you…You will enjoy shooting one…

  • James

    Yes, the 6X45 (aka 6mm/223Rem) is a great AR15 set-up and is easy to configure. I have one with a 22″ Lilja stainless barrel (HBAR weight), 1/9 twist, standard flash suppressor and love it. I have DCM type floated handguards. I shoot mostly 80 and 85 grain bullets. Mine was set-up with a ‘near’ match chamber (asked for a suitability for 90 grain maximum bullet weight) and required me to get a custom made SB (small base) sizer die from RCBS ($97). Use W748, H335, BC2, and RL15 powders in my loads, so far. I use mine for target shooting and hunting. Glad to hear that Black Hills is going to offer the ammo, even though it’s not that difficult to load your own.

  • Has anyone seen any of this ammunition on the market? Have you seen any consumer chronograph data?

  • John

    Dakota Ammunition (Cor-Bon) has a few different factory loads available. The 70gr is rated at 3000 fps from a 16″ barrel, 85gr is rated at 2800 fps.

  • We have been making 6×45, .257×45, and 7×45 uppers for quite some time now. All of them feed better than the .223, due a less aggressive shoulder.

  • This coming weekend I am going to get out after coyotes and will be carrying my 6 x 45. It’s an extremely accurate rifle and should be an exceptional coyote gun.

  • Jason

    I have been wanting a 6.8mm AR from DPMS (full 20 inch rifle) but as I am writing this; Hornady just released a 120 grain 6.8mm ammo with a B.C. of .400! Should get interesting in which caliber is the way to go. Wonder how high up in B.C. you can get with the 6 x 45 bullets? Can anyone let me know?

  • Grenadier

    Well, it’s been the better part of two years since this discussion. I stumbled on it looking for info on the 6x45mm. Ammo is available from several sources now, including (in response to a query above) Midway.

    The 6mm may not offer a lot over the 5.56x45mm in a military rifle it does have advantages in other roles. The 6x45mm has a good record in competition, outperforming the 5.56 at distances greater than 200m. Also, the 6x45mm is legal for deer hunting in most states whereas the 5.56 is not.

    My purpose is to build a small rifle on a mini-mauser action that can be used by my young son for coyotes and deer. The 6x45mm cartridge should work well for that. To convert to 6.8SPC the rails would need reworking to ensure reliable feeding. But, with the 6x45mm, I think I can get a way with just having the mini-mauser rebored to 6mm. I also plan to add a suppressor so my son csn preserve his hearing.

  • Hankmeister

    I’ve been loading for the 6x45mm since the U.S. military began experimenting with it in the late 70s and early 80s before the adoption of the 5.56 M249 SAW. I probably have burned through 4K rounds of the stuff just tinkering with it with another 4K loaded and sealed away in ammo cans for long term storage.

    Back in 1983 I bought one of the first 6x45mm stainless steel barrels (20″) that Olympic Arms produced and since I thought the reloading dies for the new caliber was outrageous at that time, I simply used a spare RCBS .223 die set and replaced the stock expander button with a 6mm/.243 RCBS neck expander. I had to drill out the neck in the seating die and everything worked pretty well.

    Over the years I used 85 grain 6mm soft-pointed/spire point bullets of either Sierra or Speer manufacture and I don’t remember any reasonably priced matchgrade bullets in 6mm being available at the time. I used military pull-down WC-846 and Winchester 748 powder. Depending on the lot # I was using between a 24.5 to 26 grain charge. I chronographed those loads which were between 2750 and 2825 fps. Fairly respectable. The primers were somewhat flattened but I could get another .5 to .7 grains of powder into the cases without blowing out pinholing the primers.

    The loading data for powder charges in the 6x45mm is almost identical to that of the 5.56x45mm powder for powder. Though the 6mm bullet is heavier, the bore is bigger and therefore once the bullet jumps the free bore into the rifling all other factors like chamber pressure and whatnot are pretty much the same. Anyway, that’s my theory. So if you’re loading your 55 grain 5.56 with 26.5 grains of BL/C2 or equivalent medium burning powder, then you can pretty much use the same powder charge for the 6mm loading. But you’d still have to tune the loading for greatest accuracy if you’re wanting to develop a match load, of course.

    I shot some sub-MOA 5-shot groups at 100 meters and a few 2.5 inch groups at 300 meters but overall group sizes were probably around 1.25 MOA. I’m sure there would have been some significant overall improvements in group sizes if I was shooting virgin brass (I was using Lake City once-fired brass), Remington 7 1/2 match primers and match bullets.

    By the charts, terminal ballistics is fairly impressive when comparing an 85/95 gr 6mm bullet to a 55/62 grain 5.56 bullet. I think the 85 gr. 6mm bullet at 2800 fps has more energy at 300 meters than a 55 grain 5.56 at 3135 fps (the real world velocity of most 5.56 loadings, btw) at half that distance.

    The U.S. military made a big mistake jumping on the 5.56 “micro-caliber” bandwagon (after making a big mistake of adopting the M-14 instead of the superior 7.62 FAL or AR-10) instead of developing something in the 6mm to 6.5mm range. An 85 to 100 grain bullet traveling 2900/3000 fps should have been within reach of the military firearm industry even in the late 1950s. I’ve never shot the 6mm in full-auto but the felt recoil of the hottest 6mm loading in my HB-AR 6mm is probably no more than 10% greater than that felt from my 5.56 20inch AR-15/A2.

    Just sayin’.