12” 308 chamber & twist recommendations

[The Knuckle]

I’ve got a SBR’d CDG & a Nighstalker waiting on a barrel. I think I’ve settled on a 12” 308 and will primarily shoot 110-125s but would also like to shoot some subs.
Was thinking a 1-10 should be fine but why not go 1-8 twist and would you pick a different chamber for shorter bullets since subs can be loaded deeper in the case?

Thanks for the help

 

[The Knuckle]

Bumping this again.
Anyone mess around with 308 subs and still get decent accuracy with a short 1-10 twist barrel?. Maybe over thinking this but a custom barrels aren’t cheap so want to get it right.
I think most of the time I’ll be shooting 110s and 125s but definitely want to shoot some heavy subs.
Messing with a twist calculator I at least need a 1-8 twist for marginal stability using heavy subs out of a 12” barrel.

 

[NHPiper]

I found that even a 1:10 twist on an 18" barrel didn't stabilize boat tail subs. Shot the flat base sierra round nose 180-200+ grain bullets.

My guess is that if you shoot those you will be fine regardless.

A 1:8 may have more wind drift between supers/subs to account for. Similar to the issue with a 1:5 300Blk vs a 1:7. That being said, a 1:7 twist 300Blk doesn't have wind "spin" drift so you may be fine with a 1:8.

Not much of an answer, but bullet selection may be your friend.

 

[SkyScrapin]

I’ve got a SBR’d CDG & a Nighstalker waiting on a barrel. I think I’ve settled on a 12” 308 and will primarily shoot 110-125s but would also like to shoot some subs.
Was thinking a 1-10 should be fine but why not go 1-8 twist and would you pick a different chamber for shorter bullets since subs can be loaded deeper in the case?

Thanks for the help

10 Twist and shoot 155 supers and 185 Jug subs.

If you go lighter on the supers you will be extra loud, no meaningful increase to velocity and expect to hit transonic 20% faster.

 

[fast freddy]

Ive got a sub load that uses a 180 grn interlock round nose flat base and trailboss that shoots great in my guns 10 twist and 11.25, dont have any 8 or 7 twist 308 guns.

 

[The Knuckle]

10 Twist and shoot 155 supers and 185 Jug subs.

If you go lighter on the supers you will be extra loud, no meaningful increase to velocity and expect to hit transonic 20% faster.

Mind elaborating on it being extra loud with lighter supers? I’m reloading these with a faster powder and running suppressed
And you’re seeing no real benefit going lighter than 155. I was thinking that inside 600 yards velocity was more important. In reality, probably would be inside 300 since I probably wouldn’t shoot any game beyond that.

 

[SkyScrapin]

Mind elaborating on it being extra loud with lighter supers? I’m reloading these with a faster powder and running suppressed
And you’re seeing no real benefit going lighter than 155. I was thinking that inside 600 yards velocity was more important. In reality, probably would be inside 300 since I probably wouldn’t shoot any game beyond that.

I’m using H322 for reference.

125s and 135s peaked at 2700fps IIRC with no change in pressure signs, I kept adding powder but never got increased speed. It was blowing all the excess out of the suppressor and it was loud as hell with a can. Every charge was. The projectile wasn’t heavy enough to support great burn %.

As soon as I switched to a 155 hybrid, sound significantly decreased, speed barely decreased, transonic range dramatically increased, energy increased. Overall, the longer bearing and heavier projectile was the catalyst to a more efficient burn rate with the exact same powder.

I’m transonic with a 155 to 787y at 400ft ASL and 80F. Same load with a 125-135, eve tho faster, was transonic to like 650y.

The 155 has much better killing energy. The 125-135 wasn’t great on fur. Lots of runners at 300y+.

 

[SkyScrapin]

 

[The Knuckle]

I’m using H322 for reference.

125s and 135s peaked at 2700fps IIRC with no change in pressure signs, I kept adding powder but never got increased speed. It was blowing all the excess out of the suppressor and it was loud as hell with a can. Every charge was. The projectile wasn’t heavy enough to support great burn %.

As soon as I switched to a 155 hybrid, sound significantly decreased, speed barely decreased, transonic range dramatically increased, energy increased. Overall, the longer bearing and heavier projectile was the catalyst to a more efficient burn rate with the exact same powder.

I’m transonic with a 155 to 787y at 400ft ASL and 80F. Same load with a 125-135, eve tho faster, was transonic to like 650y.

The 155 has much better killing energy. The 125-135 wasn’t great on fur. Lots of runners at 300y+.

Interesting, exactly why I asked. Thanks for the explanation!

 

[Bearcatrp]

My 300 BO has a 1:8 twist that I shoot 190 Hornady subs. Sub MOA @100 yards. 1:10 for 308 should be fine for subs. Just have to find the right heavy bullet that works for your barrel. My 12.5 inch barreled 308 shoots 168 Amax ok. Been experimenting with lighter pills. Good luck.

 

[waveslayer]

My 17" MRAD loves the 220 and 190 for subs, but it has a 1/7 twist