Slow twist Blackout project thoughts?

[2bad4u2]

I've got a Broughton .308" 1:11" twist barrel that can be finished to a 22" barrel length. For shits & giggles, I was thinking of chamberring it in 300 blackout to see how fast I can push 110gr.-125gr. bullets with decent accuracy. This is going to be a bolt gun project so no worries about being over gassed.

Any ideas to what I could expect for velocities over a 1:8" twist 16" barrel? Sorry, I don't have Quick Load.

Thoughts?

[300Blk]

You know twist has no effect on velocity, right?

It may have better accuracy, but probably not. The govt testing I know of compared 1:8 to 1:12 in 308 an accuracy was the same.

[2bad4u2]

Hi Robert,

Yes, I was aware twist has little affect on velocity. I simply posted what I had for informational purposes. With the slower twists, I know it limits my bullet selection to the lighter weights which is fine because the whole intent of the exercise is to see how fast I can drive the smaller bullets with a moderately long (for a 300 BLK) barrel.

[300Blk]

I will say that twist has no effect on velocity (unless you are talking 1:3 twist or something).

So I claim that 1:4 twist and 1:12 twist will be the same velocity.

[2bad4u2]

Yup, that's fine. Any idea what a person could expect for velocities going from 16" to 22" with 110-125gr. bullets?

[300Blk]

130 fps with a 110 grain.
115 fps with a 125 grain.

Not all that much, which is why virtually no one does it, except for him:

http://bulletin.accurateshooter.com/201 ... nationals/

[2bad4u2]

Thanks for the info Robert. I would have to agree that for the minimal gains it's not worth the effort. I'll shelve the idea and use the barrel for another cartridge.

[advntrjnky]

Sounds like a project for the 7.62x40WT, 30hrt, or a .30cal TCU cartridge if it is a small action you want to play with. I know my 30hrt got 2550 easy out of a 20" barrel AR and 125gr Sierra Pro-Hunter. A little more barrel, QuickLoad, and choosing a good powder should get you quite a bit more....I never pushed it, just wanted it to work with moderate pressure and hit 30-30 velocity. I have always wanted to play with the 7.62x40 to see what it can do by maximizing its expanding chamber phenomenon.

advntrjnky

[sherpa]

I have a bolt gun with a 1-10 22" barrel. My results are basically what Robert states. For a 110, 130-150 fps gain over advertised velocity from a 16". I also think it will stabilize heavy slugs as long as its supersonic. But I havnt tried it yet with anything over 168's. Im going to try some 220's eventually.

[robrob]

I'd chamber that barrel for 308 Win or 300 Win Mag. There's no need for a long barreled 300 BLK.