1:10 vs 1:12 twist for cast loads in the 308 Win

T

theshootist

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Does anyone have any experience with or knowledge about whether the slower 1:12 twist really shows a noticeable advantage over the 1:10 twist for achieving higher velocities while maintaining accuracy? If there is an advantage, by how much? Would the potential advantage be marginal or significant enough to noticed in the field for longer distances?

I have 165, 180, and 200 grain bullet molds in .309 diameter. I'm using sorted clip on wheel weights water quenched, lubed and sized to .309, with gas checks.

I'm just wondering if it will be worth the trouble to sell my still new 1:10 twist 308 bolt gun and buy one with a 1:12 twist instead. The main purpose of this rifle would be for shooting steel plates at the furthest distance possible limited only by the accuracy achieved by the load.

Thanks for your help!
 
Im quoting a guy with lots of experience with cast
the fastest you can push it plus /minus is

10”………...1666…………..1944fps

11”………...1833…………..2139

12”…………2000………….2333 Fps
 
Wow, approximately 400 fps advantage. Seems like a fairly substantial gain in velocity. Perhaps it may indeed be worth having a 1:12 over a 1:10 for cast loads. Thanks for the input.
 
I'd try it first, before I traded off the barrel. I haven't made a huge effort to achieve high velocities, as it's usually at the expense of the best accuracy, but did do a work up in a
30 06 with a good smooth 1:10 barrel, the Lee 150gr flat nose design cast with ww + 2% tin water dropped and H4895 powder, hand lubricated with Canadian Tire Moly grease. If I remember right it got to 2540 fps before the accuracy disappeared, was still +/- 2 to 21/2" at 100yds for 5 shot groups. Maybe read "Jacketed Bullet Performance with Cast Bullets" by Veral Smith of Lead Bullet Technology.
Grouch
 
as a "general" rule the slower twist will allow a cast bullet to travel faster while maintaining acceptable accuracy. The cast bullet alloy can only take so much torque during the initial acceleration process before it strips lead off the bullet surface. Using slower burn rate powders (relative too cast bullet shooting) may help in this regard.

I posted an explanation of some of these effects on another thread here. Look up "Cast Bullet Shooting Has Taught me A Few Things Over The Years". I hope this may help.

I know some shooters shoot the 1:10 twist just fine, but normally not much past 2000fps. It boils down to what you have planned with the rifle in question.
 
Are you casting cause you like casting? saving money?

I just shoot the NORC stuff at 40c/round for fun/gong ringing.
Reloading with VARGET/H4895 is 24c powder/ 4c for primer, say 5c brass leaves 7c for bullet. Not much savings.

Get 1/2MOA from SMK reloads at 80c each.
Get 1MOA from NORC at 40c each.
 
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