Explaining to me about barrel twist rates on an AR

[Jose]

So I'm starting to look for an AR again after having sold mine a couple of years back. School me on the twist rates as I've seen Bushmaster, Colt, and S&W have different rates like 1:7, 1:8, and 1:9 and what they mean.

[Craizie]

No comment on the twist rate, but I have an LR308 I'll sell ya!

[Jose]

Not looking to purchase right away and I'm sure it's more than what I'm looking at spending.

[Denny]

It's the amount of spin from the grooves in the barrel as the round travels through it. It provides stability and increases accuracy, speed and distance.

[Moose242]

What weight bullets do you normally shoot?

[Denny]

My AR is 7:1 and my .308 is 11.25:1.

I've heard both sides say that a higher rate is either well worth it and I've heard that there isn't much difference. Who knows. I haven't played musical barrels to find out. I imagine that its value comes into play more with the distance you're looking to shoot.

[Vertnut]

So I'm starting to look for an AR again after having sold mine a couple of years back. School me on the twist rates as I've seen Bushmaster, Colt, and S&W have different rates like 1:7, 1:8, and 1:9 and what they mean.

The length in inches it takes for the bullet to make 1 revolution... 1:7 is 1 revolution every 7 inches. 1:8 is 1 revolution every 8 inches, etc.

[Denny]

I wonder how well this works

http://kwk.us/twist.html

[brandon01rt]

Are you wanting to just shoot 55gr FMJ or heavier rounds?
1 in 7" or 1 in 9" should cover you for the heavier ammo as well as some of the lighter.

[Sleeper]

Keep in mind brl length.

For 99% of the world 1 in 9 with a 16 inch brl is fine.

Ive never shot anything under 50gr and nothing over 64gr. All shot fine, but my gun is weird and really likes 55gr flat base projectiles.

[JP135]

Different twist accommodates different bullet weights. I can't remember the exact formula, (seems like lighter bullet = more twist to stabilize bullet) but go to ar15.com and search for twist rate and bullet weight.

[CJ]

Standard twist rate is 1:10 for an ar10. Its how many inches for a full rotation. 1:10 means 1 full revolution in 10", so 1:7 twists faster, 1:11 is slower. Heavier the bullet, more twist you need. Barrel length also has an effect, more time to twist, more stability. So longer barrels need less twist to achieve stability. For a match barrel you would want a 1:10 24-26" which is fine for 170gr projectiles. 26" is the sweet spot for velocity.

[dee]

Twist will determine how long of a bullet you can shoot. Other stability factors are altitude , the achievable velocity and temperature.

[Semper299]

So I'm starting to look for an AR again after having sold mine a couple of years back. School me on the twist rates as I've seen Bushmaster, Colt, and S&W have different rates like 1:7, 1:8, and 1:9 and what they mean.

Generally speaking, a 1:9 will shoot up to a 69 grain bullet accurately. Any heavier than that, you will want to drop to a 1:7.

The most common rounds are 55-62 grain, which will shoot just fine out of 1:7, 1:8, or 1:9.

You don't want to shoot 40 grainers out of a 1:7, just like you don't want to shoot 80 grainers out of a 1:9. If you are not going to extremes either way with bullet weight, it really does not matter which one you get, IMHO.

[CJ]

Ignore my post, I thought we were talking about AR-10's here.