300 Blackout Optimal Twist Rate

[IslandTime]

I'm working on a 300 Blackout build with a 16 inch barrel. Most of the the industry seems to be moving to 1:7 for the barrel twist as a compromise. However, I don't plan to use the rifle for subsonic suppressed. I just plan to use it for supersonic commercial type loads for hunting and plinking, not suppressed. This being the case, would I not be better using a 1:10 twist barrel?

I emailed AAC and all they said is the industry is moving to 1:7 and I could use what ever I wanted for twist. Did not really answer the question of what twist would be optimal considering my usage. Any input appreciated. Would like to get the barrel on order

 

[ksthomas]

Re: 300 Blackout Optimal Twist Rate

IslandTime,

The heaviest (longest) bullet you'll ever use is the determining factor in selecting a twist rate. Since the 300 BlkOut is intended to be used with a 220 or so grain bullet for subsonic loads, that's where the fast twist suggestions come from. If you're going to be using 125-135 grain bullets as the heaviest in your rifle, then yes, you can certainly go with a slower twist. A 1x12, or even a 1x14" would be no problem at all here, but will limit you to the lighter bullets. With the faster twists, you have the option of the entire range of bullets at no real penalty.

 

[IslandTime]

Re: 300 Blackout Optimal Twist Rate

Kevin thanks for the information. I only plan to use the lighter bullets and was wondering what one gives up in performance if you go with say 1:7 16 inch instead of a 1:10. I assumed there was some loss of optimum performance with lighter bullets by using say a 1:7, but perhaps that's not an issue...

 

[ksthomas]

Re: 300 Blackout Optimal Twist Rate

IslandTime,

In this venue, you give up absolutely nothing by going with a faster twist. It has no real impact on pressures, accuracy or performance. Benchresters generally want a very low stability factor (on the order of SG 1.3-1.4 at most) as a higher SG magnifies any jacket concentricity problems in the bullets. We're talking differences in group sizes measured in the thousdandths, which isn't normally what we do. By the time you're looking at 1/2 MOA, the twist issue becomes meaningless. The flip side, should you go with a slower twist, is that it really does preclude you from ever using those long, heavy bullets that the cartridge was designed for. That's a call you need to make for yourself, but I just don't really see that much of a positive upside to that position. Hope that helps!

 

[IslandTime]

Re: 300 Blackout Optimal Twist Rate

Thank you sir! Appreciate the input.