Looking for bullet for my AR15

[Tuna]

The lighter the bullet the slower the twist rate. For a 52 gr. bullet a 1 in 12 twist or 1 in 14 twist is best right up to 60 gr. The heavier the bullet the fast twist is needed like a 1 in 7 for 62 gr. and up. A 1 in 9 twist is an all around rate that will work with most bullet weights but favors a heavier bullet a bit better.

[wildbill1]

This is certainly true although one is not as likely to overstabilize a bullet with a fast twist as understabilize a bullet with a slow twist. In other words, a light bullet will likly stabilize fine in a fast twist, but a heavy bullet will likely not stabilize at all with a slow twist.

I'll agree that the 1/9 works for a wide range of bullet weights, but it's been proven that even the 1/7's work fine with light bullet loads. The exception is thin jacketed varmint bullets which can self-destruct if driven too fast due to excessive spin.

I have a 1/8 stainless steel Rock River 16" mid-length barrel that I shoot more than any other and I shoot everything from 52 to 75 grain bullets with great success.

[snakehunter]

The lighter the bullet the slower the twist rate. For a 52 gr. bullet a 1 in 12 twist or 1 in 14 twist is best right up to 60 gr. The heavier the bullet the fast twist is needed like a 1 in 7 for 62 gr. and up. A 1 in 9 twist is an all around rate that will work with most bullet weights but favors a heavier bullet a bit better.

Actually, it is not the weight of the projectile but the length of it that is important in determining the twist rate needed to stabilize it. Longer bullets require a faster twist rate.

[Former Cav]

I was shooting NRA highpower "AR-15 service rifle" and had a 1 in 9 twist upper.
It would shoot 68/69 grain bullets accurately. (never tried the 55's in this barrel)
75 grain hornadys would ONLY WORK sometimes.... and 77 or 80 Sierra match kings would NOT group at all.
I got rid of the 1 in 9 upper and bought a 1 in 8 (and a 1 in 7.75 for the "space gun)
It would shoot the 77's and 80's great (both the 1 in 8 and 1 in 7.75).
I tried the 55's (which shoots real well in a prairie dog rifle that is 1 in 12) and it was a shotGUN pattern.
I've been using 24.5 grains of Varget with the standard small rifle winchester brand primers.
the 1 in 8 barrel is a DPMS brand (service rifle)
the 1 in 7.75 is a Krieger SS barrel in a Rock River ARms flat top (space gun or target rifle)