6x45mm makes a comeback

Steve Johnson
by Steve Johnson

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
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • Grenadier Grenadier on Nov 12, 2011

    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 Hankmeister on Nov 21, 2011

    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'.