I load for a Ruger Mini-30 and have tried just about every powder you can think of. First let me say that only your rifle can tell you what powder will produce the best accuracy. IMO it is best to pick up a few different one pounders of powder and run some tests to see what your rifle likes. Nothing worse than having an 8 pounder gathering dust because your rifle doesn't like it.
If you want ball powder your looking at AA1680, H335, Ramshot X-Terminator, BLC-2 and AA 2230. AA 1680 is on the fast side of the burn chart and works very well with bullets 125gr and under. The others are slower burning and work better with heavier bullets 130gr and up. For the light bullets my choice is AA 1680 for the heavies I like X-T.
There is a lot more extruded powders to choose from for the 7.62x39. Most of these are very fine and relatively short cut so they meter with ease, the exception being IMR4198. For the lighter bullets 125gr and under I have a fondness for R-7, H 4198 and AA 2015. H 4198 and R-7 run neck and neck in the accuracy dept, but H4198 has a slight edge in velocity. AA 2015 takes top honors in accuracy, but is a bit slower in fps. For bullets 130gr and up I have two favorites, H322 and VV N-130. Outstanding accuracy and velocity. If I had to pick just one I would go with N-130, great stuff.
Don't limit your loads by sticking with the .310-.311 bullets. There is a whole host of handloaders out there that are getting excellent accuracy with .308 bullets in the larger bores. 125gr Ballistic tip comes to mind.
Do you plan on hunting with this round? If so, it's important that you choose a bullet that will perform and the reduced velocities of the 7.62x39. Many of the 150gr bullets in .310-.311 are pretty tough skinned and will not perform well on deer sized game, they may just just pencil through. Bullet selection is key in a tiny round like the 7.62x39.
After hunting season I will be experimenting with VV N-120 and Norma N 200. I have high hopes for these two powders and I'll let you know how they perform.