1/7 Twist vs 1/9 vs 1/12 for 5.56

[YeeHaa]

The USAF testers that blew the whistle on cold weather stability noted that the 1:14″ twist would likely be adequate if they switched to a 55 grain flat-base bullet. However, this would reduce the effective range of the cartridge.


but the military sometimes has fairly loose standards of accuracy; the M16A1 couldn’t be sent to depot as long as it was accurate within 7 MOA.

http://weaponsman.com/?p=7291

 

[georgel]

Eh, it's Air Force.

The comments section was very interesting, with some very well read people.

I really like the 75gr OTM bullets. I need to do some cold air testing.

 

[AR10ShooterinNC]

I have an AR with a 20" 1/9 and it will put 69gr SMK's into 1/2 inch at 100 yards.

 

[Ghost1]

Isn’t 1:8 the best of all?

 

[AR10ShooterinNC]

Isn’t 1:8 the best of all?

For a general use AR in 223, yes I would say the 1/8 is best. 1/8 will cover all bullet weights up to the 77 SMK. If you wanted to shoot the 80+ gr bullets, I would look at a 1/6.5 twist.

 

[11B CIB]

Isn’t 1:8 the best of all?

I am really liking the 1:7.5 twist with Intermediate gas I have. Stabilizes extra long bullets (70gr TTSX,73/75gr ELDM, 77gr TMK) and is the softest shooting AR I’ve ever been behind

 

[WadeWatts]

My 1/9 seemed to work fine with some loads I did up with some Hornady 75gr. No accuracy or keyholing issues out to 100m. Maybe long range accuracy would be very poor.

I think the 1/7 vs 1/9 issue is a little overblown, especially since most people are shooting 55gr anyway.