Twist Rate for AR15

[Alex45ACP]

What is the best twist rate for a fun/SHTF AR w/ 16" barrel.

From what I've read 1:7 works with heavier bullets than 1:9 but may not work as well as 1:9 with lighter bullets. This makes me lean toward the 1:7 because I won't be hunting prairie dogs or anything like that, but the ability to use heavier bullets might come in handy. Is there anything else I need to consider?

What would YOU get?

 

[1911user]

1:7 is the easy answer. It will work for anything but the thinnest jacketed varmint rounds. The latest popular ammo is heavy (75-77 grain) match-grade hollowpoint ammo loaded to NATO pressure and 1:9 twist is generally not fast enough to stabilize it. The old 1:12 (vietnam era) doesn't have a prayer of stabilizing anything much over 60 grain ammo. 55 and 62 grain FMJ will shoot just fine from a 1:7 or 1:9 barrel. 1:8 is also fine, but 1:7 is much more common since most military barrels are 1:7 twist. 1:8 tends to be used for long range target barrels especially by Hi-Power Rifle shooters.

1:9 isn't a horrible twist rate and 69 grain match hollow-point ammo is nothing to sneeze at. It's great for everything except the 75-77 grain match ammo.

 

[vanfunk]

1/7" for the reasons stated in the above post.

HTH,
vanfunk

 

[Bartholomew Roberts]

I would go 1:7 or 1:8. Both will handle a wide range of ammo with no problems. However, a new 1:9 will usually do well with heavier ammo initially; but you will be right on the borderline. Weather, barrel length, and round count will all affect how well 1:9s handle the heavier ammo.

 

[BIGPHIL]

If you are going to shoot 55gr - 62gr ammo, go with the 1 in 9. If you think you will ever want to shoot some 69gr or heavier, go with the 1 in 7".

I think the 1 in 9 barrels are a lot more common. I shoot 77's out of my 1 in 8 competition rifle. I have shot 69's out of a 1 in 9, 16" barrel before. Ok on accuracy, but not as accurate as with 55 grain bullets.

 

[Dr_Pain]

Isn't 1:7 what they use in the millitary??

 

[Alex45ACP]

Isn't 1:7 what they use in the millitary??

Yes.