So after alot of experimentation I have concluded the powder in Bulgarian silver tip is very similar to h4895, apparently from. 223 I have used it in. 308, 303 brit, and 45/70, and h4895 data works and the powder has same density having said that it's only true of the span can I pulled apart, but if anyone ever wants to try the same thing start with h4895 data and reduce an extra 10% just to be safe
Never had experience loading 300 blackout.. And guessing that the pulled powder from 7.62x39 might be a little faster than the stuff I pulled maybe something like a h4198 maybe.. Total guess.. You would have to pull some weigh the charges and do some research to try and figure out what the powder is similar to, but be safe if you go down this road