AR 15 Twist Rates

[WOLFIE]

I don't post often but enjoy reading pistol forum and learning. I am trying to decide between a 1 in 9" twist rate or a 1 in 8" twist rate for a new AR 15 : 5.56. The barrel length will be the standard 16 inch legal length so the rifling will be close to 14.5 inches due to the muzzle device. Regarding this type of barrel, what bullet weights will 1 in 8" twist rates stabilize well with no problem and the same question for the 1 in 9" twist rate ? Is the weight of the bullet important or is the length of the bullet what really matters ? If it is the length of the bullet that matters, is it the length of the bullet that contacts the rifling ?

[SamuelBLong]

1:7 and 1:8 will stabilize everything up to 77gr

1:9 - you're looking at 55gr - 69gr. Depending on load, sometimes it will stabilize the 75gr loads, but it's gun / altitude / velocity dependent.

The bullet length is what matters most when it comes to stability. The longer the bullet, the faster it must be spun to stabilize.

Err on the side of the faster twist - 1:7 or 1:8. Better to be more stable than less. There's almost no reason to pick the slower twist rate these days.

[LittleLebowski]

Honestly, it's easier to get a 1/7 over a 1/8. Get a 1/7 in case you ever want to use heavier bullets.

[RoyGBiv]

Consider ammo cost & availability....
Low-cost plinking ammo is more frequently found in lighter weight configurations around here. YMMV.
I find I have to search a bit farther to feed my 1:7, but not inconveniently so.

I've had luck finding 62gr American Eagle at Wally World the past few months and it runs through 1:7 well enough for my (modest) capabilities.

[orionz06]

Low cost ammo shoots fine out of 1:7 barrels.

[LittleLebowski]

Low cost ammo shoots fine out of 1:7 barrels.

Yup.

[WOLFIE]

I would like to thank everyone (thank you).
Will 1:8 produce good accuracy with 55 g bullets when using a 16" barrel?

[LittleLebowski]

I would like to thank everyone (thank you).
Will 1:8 produce good accuracy with 55 g bullets when using a 16" barrel?

Yes. So will 1/7 if you can't find 1/8 or if 1/7 is cheaper.

[WOLFIE]

Yes. So will 1/7 if you can't find 1/8 or if 1/7 is cheaper.

I will keep 1:7 in mind then. I am currently leaning toward a Rock River Arms rifle with a 16 " stainless 1:8 barrel. It has a mid length gas system and two stage trigger.

[orionz06]

Why RRA? Their two stage triggers, the national match ones, fail like clockwork to the point where a local guy has two so he's not without one when it gets warrantied.

There is generally much better out there for the asking price of RRA, as well as other reasons that may or may not matter to you.

What's the end configuration looking like?