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Originally posted by H&K-Guy:

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Originally posted by mark_a:
Apparently this is a good learning opportunity for me. How serious is the concern for stabilizing a 220 gr sub in a 5.5" barrel?

When I talk to people about my 300 blk pistol I describe it as a really accurate 1911.

Your standard 1911 seems to fire a 230 grn ball bullet in a five inch barrel with a twist rate of 1:16. The Virtus, by example, has a 1:5 twist rate. So, even with slow burning powder (if that even matters at this point), it is not going to have the same characteristics as your average 1911. They will behave completely different.

Then there is the bullet's composition. As you said, it is a different length, in a 7.62 style (or, 30 cal.), instead of a .45 caliber style (11.43 mm) bullet.

The slower twist rate in a 5.5 inch package, even with the smaller diameter, is going to require a longer barrel to stabilize, especially traveling at sub 1125 FPS (sub-sonic). And at that, I would only try to suppress 1050 FPS, or less, in that round.

I have a Wilson Combat 300blk upper -- 11.3" barrel with a 1/7 twist. I don't find blackout ammo to be as accurate as its 223 counterparts. Of course I've only shot supersonic ammo in my 223s. Buddies I compete with who have 300blk ARs also find accuracy challenging. The best accuracy appears to be with match-grade supersonic ammo in the 110 grain (like Hornady Vmax) to 125 grain (HPBT match) ballpark.

I've tried only a couple of subsonic loads in my upper. Ball ammo only -- not the match loads that use the heavy AMax and SMK bullets. For ball subsonic ammo out to maybe 25 yards, the blackout isn't all that more accurate than my match-grade 45s (Ed Brown, Kimber, Sig) with ball ammo. Further our, the optics on the blackout upper from prone position produce noticeably better results than iron sights on a handgun held off-hand. No surprises here.

In theory, my Wilson's 1/7 twist rate allows the use of a wide variety of bullet weights and types, both subs and supers. The Virtus' 1/5 twist rate is really fast. I didn't realize any company produced such a fast twist blackout barrel. The Virtus has to be designed with subs in mind -- the twist rate may be too fast for many supersonic bullets.

I use a can for all my 300blk shooting. For me, any AR being suppressed makes sense.