I just bought one and am waiting for it to arrive. I must admit I have only heard about their accuracy but I think the OP must have a very good version of the gun. I am expecting 3 - 5 inches and hoping for better with handloads.
If anyone has a good load and doesn't mind sharing I would like to have a starting point for my testing.
Please note, the OP said his was an older version of the Mini 30. Newer ones have better barrels. Not saying his isn't a good rifle, just saying newer ones have better accuracy potential.
123 gr. VMax bullet; WW case; LR Federal Match primer; 24.5 grs. of H4198
(Note: Start at 22.5 grs. H4198. While not max loadings these aren't starting loads either. These loads are safe in my rifle. Check carefully that they are also in yours!)
Reloader 7 is a good powder for this round.
There are a lot of negative opinions floating around about the Mini 30 and accuracy. Most aren't substantiated. You will find at least one in this thread already. The Mini 30 is good at what it was intended for. A quick to grab, quick to acquire a target, sturdy, dependable rifle that goes anywhere easily. You can achieve acceptable hunting accuracy or better with this round. The 7.62 x 39 has good knock down power for medium sized game, an improvement over the Mini 14. As it is, it will never be a tack driver however the stories and second hand opinions about it's poor accuracy are usually exaggerated- especially regarding the newer versions.
This is a 10 shot group shot at 110 yds with the Mini 30. Group size: 2.044 inches. This was prior to the trigger job and it shoots better now. I just don't have any pics of the new groups yet. 5 shot groups now are, on average, just over an inch.
Please note: This was a 10 shot group not a 3 or 5 shot group. 3 shot groups are a waste of time IMO, as you can get real lucky and think you have something going when you don't. 5 shot groups are a good indicator, 10 shot groups give you a real world idea of what your rifle is doing. Once again, my opinion, not necessarily everyone else's.
You can get Lapua brass for this cartridge if you are wiling to spend the extra $$. It really helps.
Hunting loads are averaging 2157 fps at the muzzle with the 123 gr. Hornady SP. These are not max loads.
Finally, I don't recommend shooting corrosive surplus through the Mini 30. I know that lots of guys do. Just not worth it to me. Components are cheap and easy to come by.