1/7 vs 1/8 barrel twist

[cropsey]

Hi,

I want to put together a mk 12 spr rifle. I know that the 1/7 is the correct mil spec twist rate, but the uppers with that rate are currently backordered. As a practical matter, how much of a difference would it make to go with a 1/8 twist Douglas barrel? To be honest, I don't know how much mk 262 77 grain ammo I'll be shooting due to cost. I'll probably be using a fair amount of 55 grain range ammo. How much worse would the performance be?

thanks.

[T2C]

1/8 twist is a good all round twist rate. I've fired some decent scores at 200 yards with a 1/8 twist barrel and PMC 55g FMJ. The Junior High Power Team in our area shoots with 1/8 twist barrels at Camp Perry every year and they do quite well.

[17K]

If it'll fit in a magazine, 1/8 will stabilize it.

[T2C]

If it'll fit in a magazine, 1/8 will stabilize it.

And then some. 1/8 barrels stabilize my 600 yard loads, which are too long for a magazine and have to be loaded one at a time.

[vicious_cb]

As a practical matter, how much of a difference would it make to go with a 1/8 twist Douglas barrel?

Not a damn thing, worry more about the reputation of the barrel maker than the twist rate.

[lordmorgul]

1:8 works fine with my 20” SPR build and 75gr OTM, 70gr GMX, and 73gr ELD bullets loaded to magazine length.


Andrew - Lancaster, CA
NRA Life Member, CRPA member, Calguns.net contributor, CGF / SAF / FPC / CCRKBA / GOA / NAGR / NRA-ILA contributor, USCCA member - Support your defenders!

[FightinQ]

And then some. 1/8 barrels stabilize my 600 yard loads, which are too long for a magazine and have to be loaded one at a time.

80 SMK or 75 ELD? I'm curious. What barrel length also?

[T2C]

80 SMK or 75 ELD? I'm curious. What barrel length also?

80g SMK shot out of a 20" barrel.

[1168]

If it'll fit in a magazine, 1/8 will stabilize it.

This has been my experience, as well. However, given the choice, I prefer 1/7. I launch long bullets through short barrels and suppressors, so it just makes me feel better. But, I’ve had no issues with 1/8, even with long copper bullets.

[markm]

80g SMK shot out of a 20" barrel.

We run those on occasion out of a 1/9 nominal, 20" barrel with no issues. Unless the OP is shooting M856 tracer in a short barrel, 1/8 is plenty of twist.