Can someone explain a 1-7 twist barrel please?(ar-15 .223)

[Franky4Fingers]

Can someone explain what the hell this is for, I've been doing a lot of bullet research, manufacturing recommendations, mathematical equations and nothing warrants a 1-7 twist barrel. At most a 1-8. I think a 1-7 would be for a 80+ grain bullet...which from reloading experience is too damn long for a AR 15 with a magazine.

input?

[hare12y]

I have 1-7 in an lmt upper and it shoots 62 grain rounds really well, the lower twist will shoot a heavier grain bullet and I think lately many uppers are made in 1-7 twist...I love mine.

[Enfielder]

There's much on the web about this. 1:7 is supposed to be better for stabilizing heavy bullets. 1:9 stabilizes 55 gr and 62 gr bullets fine. 1:7 for greater than 70 gr bullets that long range match shooters use.

[harold63]

Can someone explain what the hell this is for, I've been doing a lot of bullet research, manufacturing recommendations, mathematical equations and nothing warrants a 1-7 twist barrel. At most a 1-8. I think a 1-7 would be for a 80+ grain bullet...which from reloading experience is too damn long for a AR 15 with a magazine.

input?

I do not disagree with you sir. I will not go into all of the logarithms, trigonometry, geometry, and algebraic equations that are involved in what you are asking, but simply say that my 1 in 9 twist barrel will put 72 gr. bullets in a one inch hole at 200 yards off of a rest. I think that the bullets are being stabilized. Never have I seen an oblong bullet hole in a target. I can't do tons of equations, but I can experiment with different weight bullets out of the same barrel and can say that from 55 to 72 gr, I do not see any difference in accuracy out to 200yds. That is good enough for me. I can see where a heavy bullet like an 80 grain would need to spin a little faster to go straight, but like you said, too, the bullet would start to get too long. I know guys at my range that shoot tons of 55gr out of a 1 in 7 barrel and never have problems. I believe certain types of fragmenting bullets may need to be more matched to a specific twist rate, but for general purpose bullets, I do not see hardly any difference in performance, and I am no guru, but I try to observe this as much as possible, with cold, warm, and hot barrels. I am not convinced, myself. Good question that I wish could answer better or had the knowledge to answer better.

[SCBaldr]

The short answer is that the 1 in 7 twist is the Military Specification. Why? I don't know. It could have just as easily been a 1 in 8.

[chp1911]

I dont know if this is what you are asking but 1in7 refers to to the rifling making one full twist in 7 inches.

[Tim Ault]

Your exactly spot on a 1:7 is more than needed in most situations and bullets fired most 1:9 will be fine with a 69 and even a 75/77 gr. Same situation occurs with most 30 cal rifles being made these days with a 1:10 twist who the heck is still shooting a 220 gr. RN bullet these days ? a 1:14 is fine for a 168 1:12 for the 175, if these fast twist rates are so great why are the BR guys using a slow as possible twist they can get away with! Why because thats where the accuracy is.

[knight0334]

Your exactly spot on a 1:7 is more than needed in most situations and bullets fired most 1:9 will be fine with a 69 and even a 75/77 gr. Same situation occurs with most 30 cal rifles being made these days with a 1:10 twist who the heck is still shooting a 220 gr. RN bullet these days ? a 1:14 is fine for a 168 1:12 for the 175, if these fast twist rates are so great why are the BR guys using a slow as possible twist they can get away with! Why because thats where the accuracy is.

Velocity and bullet length are the factors. The faster the twist, the more torque on the barrel and receiver. Faster twists also cause more resistance and friction.

With the longer barrels that bench rest folks use they can gain a few extra hundred feet per second. That added velocity means they may not need a faster twist with the same length of bullet shooting from a shorter barrel at lower velocities.

[cdi]

Velocity and bullet length are the factors. The faster the twist, the more torque on the barrel and receiver. Faster twists also cause more resistance and friction.

With the longer barrels that bench rest folks use they can gain a few extra hundred feet per second. That added velocity means they may not need a faster twist with the same length of bullet shooting from a shorter barrel at lower velocities.

That's pretty much it-
The tighter 1-7 twist is needed to stabilize LONGER, not heavier bullets. The military went to 1-7 to stabilize the longer nato tracer ammunition.

All things being equal, the tighter twist barrels do not appear to last as long as the slower twist barrels.

[animalmother85]

My SAM-R has a 1-8. My Noveske has a 1-7. My 700 SPS has a 1-9. I'm happy with all of them. They all shoot well.