I am told that IMR 7383 is very similar in burning rate to 4350 but much bulkier. I am tempted to apply this by using a case full of 7383 anywhere the weight of such charge is the same or reasonably less than 4350 charges for the same case and bullet.

If anyone has actual data or a better approach, please let me know. I'm planning to start with 120 grain bullets in a .25-06, but I'll wait a week or two for answers to come in first.

Do you mean IMR 7828???

I did some checking. It seems to be a bit faster than I was told and a bit less bulky than I feared. I think I have a handle on what I am dealing with, but all info would be much appreciated.

I'm not clear on the relative speed (was under the impression that it was on the slow side) or bulk of 7383, but I was told by a surplus powder merchandiser who sells it that it burns very dirty and he implied that it is not particularly suitable for serious shooting.

Well, the .50 spotting rifle round is much shorter with less capacity than the .50 BMG round. It also fires a phosphorus "shell", probably lighter than the .50 BMG projectile, which bursts on impact, and at a much lower muzzle velocity (+ - 1600FPS), to match the 106mm RR main gun trajectory. So it is likely that that powder is faster than regular .50 BMG propellants.

Leftoverj, I posted this on the Shooters' Talk Cast Bullet Bd. about 2 weeks ago, but in using 7383 in my .243Win with jacketed bullets, I found it to be slower than 4064. Having read (on the CB Bd.) that it was similar to 4064, I used the Lyman Reloading Handbk.'s suggestion of ~34gr. with an 85gr. Sierra SP, but I actually used 36gr. The upshot was that 7383 was slower than 4064...in that cartridge. Next time I'll try 37gr., 38gr. and maybe 40gr. Btw, accuracy was only fair with 36gr. and the extreme spread was higher than I wanted. Hope this helps, ... Maven

Helps a lot, Paul.

I'm still thinking and gathering info, but I think my approach is going to to find a cartridge and bullet combination in which a case full to the base of the neck has a weight within the range for 4064. I'll chrony that to see how close the results are for what I would expect for 4064 and work from there. When I get a better feel for the burning rate, I may be willing to allow a little more airspace in the case.

.257 Roberts and .308 Win look like my best candidates for the early stages. I'm pretty sure I can't get enough in the .308 case to do myself any damage with 150 grain bullets.