AR-15 DISCUSSION: M855 AMMO AND 1:9 TWIST RATE

M855 ammo is stabilized very well in 1:9 barrels.

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Education

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[HunterKiller308]

1;9 is great for heavier loads but 1;7 is better for lighter loads

[millerusaf]

@HunterKiller308 If the load is too light, the 1:7 will do more damage than good.

[b2flyer1]

Miller in keeping with the subject or the .223/5.56 what's Your opinion of the Ruger Mini-14,and it's use of the 5.56 ss-109

[millerusaf]

@b2flyer1 What is the rifle rated at? If it's stamped .223, don't fire 5.56mm in the rifle. If your chamber is rated 5.56mm, then it should be fine.

[Everett07630]

Hey Miller, just changing the subject a bit, but what's your opinion on the new 7.62x35mm (.300 Blackout) for the AR15 / M4 carbine?

[millerusaf]

@Everett07630 Haven't looked at that round yet. Sounds interesting.

[40DegreeShoulder]

anybody who says that 1:9 won't stabilise a 62gr is fucking stupid

[MrSurgicalPrecision]

You should match your twist rate to your bullet length. LONGER bullets need faster twist rates. Weight is only a product of the length of the bullet. A 75 grain A Max will stabilize in a 1-10" twist and it's much longer and heavier than the 62 grain FMJ. I'll look around and see what bullets I have lying around and possibly do a response video explaining this further.

[zakelsey11]

very helpful thank you!!! i just bought the rock river ar-15 a2 and i haven't shot it yet but i am itching to do so and i was wondering about the 1:9 compaired to the 1:7 ratio. i am also in the air force and shoot guns all the time and your information was very educational. thanks again!!!

[greatwhitejake]

is the 1:9 twist barrels good for all 5.56 rounds including the heavy grain rounds? i had a ar15 with a 1:9 twist barrel and i bought some M855 ammunition, i started hearing people say it wasnt safe to shoot out of a 1:9 barrel so i just put them away.

[DrDaveArson]

Hey millerusaf, would it be possible for you to make a video or add photos to this video of group of the m855 through a 1:7, and a 1:9 to show the difference between the two. There are so many different answers for this question from these so called internet "experts", whether a 1:9 is best for the m193, not the m855 and vise versa. Really i just need some clarity. How well will each twist rate shoot these two popular available 5.56 ammunitions. I just want to get to the bottom of this nonsense.

[ajbrown0117]

So will a 1:9 twist 16 inch barrel stabilize a 62 grain 5.56 round? And if so what is the highest bullet weight a 16 inch barrel with a 1:9 twist stabilize?

[elox02]

By higher I meant the number (1:9-1:12) to cut someone off at the pass. I do know 1:7 has "higher" twist rate.

[elox02]

Heavy bullets through high twist rate may keyhole 77gr out of 1:9 or 1:12. But will be fairly accurate and cause massive wounds. the problem is with really light bullets 45 gr out of the 1:7 can break apart. The real factor is how it acts against soft targets not paper. I've had 1:7,1:8,1:9 twist barrels and fired 55-79 gr out to 200yds 14.5"-20" barrels. The quality of the ammo is the only real deviation in accuracy I've found not 1:7-1:9 twist although I prefer 1:7.

[elox02]

1:7 and 1:9 are fine for 62 gr. steel is lighter then lead so m855 is actually a long bullet that's what the 1:7 Is for longer bullets. Heavier lead core bullets are long as well, the twist isn't so much for the weight as it is for bullet length. The more twists the more velocity you actually lose to friction. I personally like mk318 mod 0 bullets and Seirra match king or black hills 75-77 gr they have a slower fragmentation threshold good out of a 14.4" BCM.

[CJRKENT7697]

This was very helpful information. I actually called DPMS about the availability of the 1:7 barrel and they assured me that there is a myth about that.

[paschallhouston]

What is the difference between 556/223 rem? I was told the 1:7 twist was used in Vietnam in the m16a1 and caused more damage because the bullet tumbled on impact.