5.56mm twist rates?

[Goat]

I am in the market for an AR and have pretty much settled on the Rock River Predator Pursuit 16"Carbine or the Coyote Carbine also in16". The Predator has a 1:8" and the Coyote a 1:9". What weight bullets can be expected to stabilize in the different twist rates? Goat

[josiah712]

The 1 in 9 can handle up to 75 in some cases if they are not too long.  It for sure can handle Hornady 68s and Sierra 69s.  But if your interest is this weight range or higher, then get the 1 in 8.  If you mainly want to shoot less than 65s, get the 1 in 9.

[josiah712]

Some other things to consider:
 
1 in 9 is about the end of the versatility (do it all twist rates), while 1 in 8 is the beginning of the extreme rates.  These rates are designed to increase the long range penetration of the 5.56 round.  I have heard of thin skinned varmint bullets failing (or shearing out) from 1 in 8, or 1 in 7 twist barrels.  But I can't attest to this.
 
I am very happy with my 1 in 9 twist.  It shoots 55s and 69s with equal aplomb; and my favorite bullet is the Hornady 60 grain V-max, it holds energy well enough downrange, and it's accurate and explosive.

[sk330lc]

my RRA Coyote 16" Carbine with a 1-9" has handled everything I've fed it . from a 40gr V-max to the 75gr bthp match bullets.  I have yet to shoot any bullet in this weight range that I couldn't find a load that would shoot under 1" groups at 100 yards.  saying that it Loves 60gr V-maxs I have shot several 1/4" groups with this bullet.

[helotaxi]

The 1:9 will stabilize just about anything that will load to mag length in an AR.  Modrn varmint bullets, except those designed specifically for the Hornet, will hold together just fine in the 1:7 twist barrels at .223 velocities.  I've shot 75gn Hornady HPBT in my 1:9 AR and 36gn Varmint Grenades in my 1:7s each without any trouble.  The 1:8 barrels are really only needed with the super long match bullets that are single loaded (75 & 80gn Amax and 80 & 90gn MatchKings need 1:8 or faster), otherwise 1:9 works just fine.

[cjclemens]

I have a 1:9 twist in the AR I coyote hunt with.  It handles 60-68 grain bullets really well, but it doesnt like 55's for some reason (I normally shoot 62's).  I would expect the 1:8 to handle a similar range (60-75 grain).  Its likely to handle the 68's and 75's a little better and it may be a little more finicky about the 55's and 60's.  You will, however, have to check overall length on 75 grain bullets - some wont load to AR magazine length.

[oldandslow]

I too have an AR with a 1:9 twist but it is finicky as all getout. It loves 60 gr. bullets over H4895. 55 gr. bullets not so much and 50s and under are just a waste of time. Same way with 63 gr. bullets, not so great. I have no idea why but it shoots 60 grain ones so well I'll just stick with those. I think they will kill a coyote (haven't been hunting this year) and that's all I want from it. No prairie dogs left around here.

[helotaxi]

You will, however, have to check overall length on 75 grain bullets - some wont load to AR magazine length.

The Hornady HPBT is pretty much the only one that will load to mag length. The Amax will not.  The 77gn SMK will as well but it isn't 75gn

[JeffG]

The 9 twist is reliable with a wide range of bullets. The increased rate of spin is great for reducing deflection on intermediate barriers like window glass. Certainly
not a hunting concern. My 8 twist AR gives explosive expansion, and great accuracy with 60 gr. Hornadys or better.