View Full Version : .30 Sub Sonic
02-24-2009, 09:21 PM
Does anybody shoot .308 subsonic cast boolits? I'm trying to get a 200 gr. RCBS Silhouette to shoot out of a 1 in 10 twist Encore barrel, but have not had much luck yet. I'm getting 4-inch groups at best when it stays below 1,050fps. If the velocity creeps above the speed of sound, the groups really blow up. If anyone knows of a good cast boolit design that will stabilize in that twist rate, and stay near 200 grains I'm interested in learning about it.
02-25-2009, 01:08 AM
My fast twist .32-20 (1 - 10 SMLE barrel) stabilises 100-240gr all at subsonic. You may need to tinker some more.
02-25-2009, 05:49 AM
I have shot some subsonic loads with 200 gr. + bullets from a 788 .30-30 (10" twist) in the past. Groups were in the 1 1/2" range @ 100 and 3-4" @ 200.
311299 (208 grs.)
- 7.0/231/WLP - 1,115 f.p.s.
- 7.8/4756/WLR - 1,100 f.p.s.
- 8.5/Blue Dot/WLR - 1,100 f.p.s.
I positioned the powder to the back of the case for the best results.
A friend has the Rcbs 200 mold and there is no nose support since it starts at .296" dia and tapers back to .300" at the start of the driving band. It doesn't shoot very well for him either.
02-25-2009, 08:31 AM
You should get much better than that. Cast them soft (plain WWs is fine). Minimally size them when seating the Gas jech. Use a soft lube like Javelina, BAC or LLA. I prefer deadicated cases for these loads that are well fire formed and have the flash holes drilled out with a #30-28 drill. This aleeviates the shoulder setting back from the primer explosion. It all gets the primer flame out into the case quicker resulting in less "position sensitivity" of the powder. I'd suggest working with 5.5 gr to 7 gr of Bullseye of 7 to 9 gr of Unique.
02-25-2009, 02:09 PM
I'm getting good results with a 170gr GC bullet over 16grs of 2400 and a large pistol primer. A very small dacron filler over powder helps too.
02-25-2009, 04:01 PM
I use a Lyman 200 gr. silhouette bullet w/ gc - the 311299. Fired from either of of two .308 bolt guns, a 1 in 10 and a 1 in 12, I know the bullet will fall within a 2" bullseye at 100 yds. The gc probably isn't necessary, but I size and check them a quart jar at the time for all kinds of loads. In these rifles, with 5.0 gr of Bullseye, I get 871-903 fps. No fillers and it doesn't matter whether you're pointing up or down.
4.4 gr Unique works as well with the 1 in 10. The 1 in 12 not so much. Haven't chronographed this load but it's got to be slower.
David - Welcome to the site. That was a great first post. Good info.
02-26-2009, 10:20 AM
FWIW a very good cast bullet shooter told me several years ago that cast bullets generally don't like fast twist barrels in 30 cal like 10". He recommended 12, 13 or maybe 14 twist for bullets to about 170 grains.
I have a friend who just pulled a 13 twist Pacnor off his match rifle and he is passing it to me to play with cast bullets from it. I will set it back at least one set of threads and give it a go.
Right now I am playing with 358 Win in subsonic with 16 twist barrel and it is looking promising.
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