Barrel twist for .300BLK

[Ryanxia]

Of course it's been so long since I first researched this I've forgotten most of what I learned.

Got my suppressor in for the .300BLK and going to order a barrel for a new build. I think I'm pretty set on the length of 8.5" for comfortable OAL even though I know it isn't the most optimum length.

The question is, what twist rate will be best? I will be shooting subsonic loads but also want to be able to do a mag change and send full power loads further down range. Any input is appreciated.

 

[Ryanxia]

I think I answered my own question, probably should have done a better search beforehand but still curious to see what others think.

http://www.thetruthaboutguns.com/2014/11/foghorn/ask-foghorn-questions-300-aac-blackout-rifle/
https://www.300blkparts.com/Content.aspx?PAGE=300BLK Barrel Twist Rates

 

[Elkins45]

My experience is from shooting cast lead subsonic primarily, so take it with a grain of salt. I have found there is a bit of a difference in accuracy between my 1-7 and 1-8 barrels, with the 1-7 being more accurate with the heavier bullets. I don't know if that's a general rule or if my 1-7 just happens to be a better barrel. Sample size of 1...

 

[Ryanxia]

Interesting. We shall see, I settled on a 1:7 for my initial barrel. Good place to start.

 

[vtsteve]

Palmetto State Armory has 8.5" 1:7 uppers on sale fairly often. I picked one up for $259 with free shipping a few weeks ago. Haven't had a chance to shoot it yet but it seems well built just from inspecting it.

 

[plodder]

In my questionable experience, you can't overspin a projectile coming out of a short barrel. You sure can underspin them though. I use 1/7 for a 7.5" SBR AR in .223, a 1/7 for a 10.5" SBR AR in .300BLK and a 1/7 for an 18" heavy barrel AR .223. Each of these shoot at least as well as I can.

I also have a 1/9 in a 16" barrel AR. It likes to launch knuckle ball key-holers if I try to shoot anything heavier than 69 grain projectiles.

JMHO & YMMV