Tex- I think you may have a problem with very heavy bullets in the 7.62x39. The rifling pitch is probably too slow to stabilize a long bullet, so accuracy would most likely be non existant. I have loaded squib plinking loads for many rifles over the years, and I have always gotten best results with fast pistol or shotgun powders like Unique or Red Dot. Haven't loaded anything for this round though, so can't give you any data.
I don't know what application you have in mind for the low velocity load, but if you really want to try a heavy bullet, Midway sells Remington 180 gr .312" bullets for the .303 Brit. for $15.99 per hundred. If you want a full case of powder, Accurate # 5744 is made just for reduced loads with fairly full cases. It's very bulky, and medium-fast burning. Might make a decent load if you can find any data on powder charge weight. I doubt if there is much data on reduced loads for this round since it is almost always chambered in semi-autos and of course reduced loads won't cycle the action. Sounds like a fun project though, good luck, and be VERY careful.
