10.5 inch, 1 in 7 inch barrel stabilize a 5.56 slug?

A .22 MAG has a 40 grain bullet with a 1:7 or so twist in a revolver or my Automag ll with a 4 inch barrel and it is plenty accurate. I was looking into this very thing and figure that they would only make the barrels with that advertised twist rate IF they were accurate to begin with. I would think that the same twist rates that stabilize in a rifle would do so in the shorter pistol barrel but produce less velocity. So the medium to long projectiles would be OK in that barrel offered. You could call or email and ask them on Tuesday.

I had a Sig Saur P556 pistol. It had a 10 inch barrel and I believe 1 in 7" twist. It stabilized 62 grain ammo with no problem, and I believe I tried a box of 77 gr Black Hills ammo. It shot fine. At least I think it was 77 grain.

Your results may carry of course.

I have a pistol that shoots 5.56/.223 that has a 10.9" barrel with 1 in 7 twist. I've only shot 62gr ammo through it.

Both XM855 and Federal Fusion rounds stabilized.

Unless it is gain twist rifling it takes very little barrel length to impart spin. The bullet does not somehow skip the groves the first several inches.

Mike

If you were going to have a problem it would be on the heavier side of the scale, but 77gr is some of the most popular defensive type ammo in short 1:7" barrels because it is more effective in that role at lower velocities than lighter bullets.

No worries, a 10" 1:7" should stabilize anything you can put through it.

My 7.5” 1/7 twist is stable with everything I have put through it. I run mine pretty hot to get reliable operation. Heavy and slow bullets (relative) cycles better.

The twist rate is more important than the barrel length. Some units in the military use 10" barrels for certain missions (often suppressed). With ours, we fired bullets in the following weights: 55, 62, 75, 77.

What actually matters for stability is the rotational speed (how fast it's spinning) of the bullet which is related to both the twist rate and the muzzle velocity. Barrel length matters as shorter barrels typically have less muzzle velocity than longer ones and the bullets won't be spinning as fast, and will have more tendency to de-stabilize. That said, muzzle velocities out of a 10" barrel should be fine for you.

Colt’s factory 11.5 is a 1/7.

I had a 10.5" 1:7 barreled 5.56. I never shot paper for groups, but it did stabilize 75gr pills good enough.

Group size was roughly the same as similar quality 55gr ammo and no signs of tumbling.

Tallbald said:

Thanks folks. After my purchase, I sometimes wonder if I should have saved my money and chosen the 300 Blackout, which is touted everywhere I read as a wonderful short barrel round. I appreciate everyone's thoughts. Don.

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Unless you're going to hunt with it, or want to shoot suppressed I'd stick with 5.56. Cheap practice ammo=more range time.

With good defense ammo I'd take a well placed shot with 5.56 over the wünder cartridge in a OK placed shot.

Being said, my only AR may soon be a 10.5" 300blk just because I have a barrel and a couple lowers laying around and no AR at all.

Tallbald said:

In another thread I posted my interest in a PSA AR kit. Now considering one of their pistol kits with the 10.5 inch barrel. Would the shorted barrel stabilize a 5.56 slug for good accuracy?

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Yes, I have a 10.5 in PSA 5.56 and that stabilizes everything from 55 to 77 grain. The farthest out I've managed to go with it was at a boulder to size of a 1978 Honda at 550 yards outside of Sierra Vista, AZ and a torso sized plate at Lone Star gun range in Mesquite Texas. I was kind of blown away that I could hit that far with a 10 and 1/2 inch barrel, but I could. That was with a mix of Honady 75 gr. steel BTHP and Federal 55 gr. bulk packed FMJ. I have to admit that the 'group' looked more like I took after it with a shotgun loaded with buckshot at 40 yards, but I could hit with it.

What weights would be a best choice? I just don't know, and do wonder these things. Thanks. Don.

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Heavier grain bullets (I mostly use that Hornady steel 75 gr. BTHP simply because it works well and it's cheap) seem to group a bit better at 15, 25, 50 and 100 yards (which is it's more usual range), but it mostly sees a steady diet of 55 and 62 gr. FMJ.