Subsonic 30 cal cast boolit

[singleshot]

So I'm now looking for a subsonic cast boolit for my 7.62x54r (3 different rifles). I tried to design a 240 grain on mountainmolds.com and any block I chose it said it was too long a boolit for the block. Is 240 grain too much to ask from a 30 cal mold? Any suggestions?

[scb]

Group buy ending in 2 or 3 days if your interested.

http://castboolits.gunloads.com/showthread.php?t=102895

[leadman]

Don't know exactly what the twist is in your rifles, but a Contender with a 1 in 10 twist 300 Whisper is marginal with a 206gr boolit.

My 1 in 8 twist custom barrel does fine with 206gr. They still go straight thru the paper at 300 yards.

Looked up the twist for 7.62X54r in Cartridges of the World and they list 1 in 9.5. It may work, but I favor it not working or you will need more than sub-sonic velocity.

Guess all you can do is try it and let us know.

[singleshot]

scb, great looking boolit, but I'll need a slightly larger mold, .313...

Leadman, what's the boolit design? I'm shocked 1:10 wouldn't stabilize a 206gr. I'll have to test, but depending on the actual shape, I should be able to stabilize almost 250gr+...

[no34570]

Singleshot
I ran a twist calculator http://kwk.us/twist.html and it said that a 1-10 twist would stabilize the .311 247gr bullet if you are doing a muzzle velocity of 1505fps ,you put the length 1.335,then you put in the diameter of the bullet .311,then muzzle velocity 1505 and the bullet SG values,which is lead 11.3 and it is spot on,you can go lower velocity,it then changes the twist requirement,but only a little,if it is still on 1-10.2,it should be ok,but others might want to chime in here. I'm getting this bullet for my .308Win and I have not got the gun yet :)

[Artful]

Remember it's the length of bullet not weight that counts, have you checked with several of the stability programs that are on the web, remembering they are approximations and your barrel may act differently than the calculations predict.

[no34570]

You bet me too it Artful ;)

[singleshot]

I've got 1:9.5 just as stated by leadman. Yes, most of the calculators agree with the numbers cited above.

If you don't pass through trans-sonic velocity, stability improves vs. starting super and ending sub.

My goal is to keep the boolit at or below 1050 fps.

[Artful]

for a fatter heavy bullet you might like to look at this one
http://castboolits.gunloads.com/showthread.php?t=107545

[afrance]

Singleshot,

Not sure which profiles you tried but here is a 240gr, .314, bore-riding truncated cone that is 1.243" long. Says it will fit in the 2XL blocks and at that length should be stable down to 850 fps.

http://castboolits.gunloads.com/imagehosting/thum_23654e19a27db358e.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1432)

[leadman]

The boolit I shot in the 1 in10 twist was 314299. It was marginally stable at 1,050 fps muzzle velocity when it got to 200 yards. This was out of a 10" Contender barrel with a .3085" bore, so the boolit was a little longer than if it was going thru a .312" bore. The nose on this is a long bore-rider that is a semi-spitzer design.
I use the same boolit in my 18" 1 in 8 twist Contender barrel with no problems at 300 yards. I haven't tried shooting paper beyond that yet.