I have an older Mini-30, and I've tried a few load workups with it. It is not a tack driver, I can tell you that much.
So far the only powder I have tried is H335. I have assumed it is .308 since it is an older gun (which I have since discovered may not be the case) all I have tried thus far are .308 bullets. Hornady 130SP, Speer 125 TNT, and Sierra 125 SP. The best I have gotten so far is about 2.5 MOA.
I really need to slug the barrel to find out just what I have. I suggest you do the same. Some people use .308 bullets in .310 barrels with some success.
Some interesting things I have noticed:
I have to crimp. If not, the bullet will jump when chambered. I determined this by manually chambering rounds until I determined just how much was needed. Apparently the bolt slams the round into the chamber fast enough for it to act like a kinetic bullet puller.
The ramp and chamber opening have very sharp edges. With soft nose bullets, I was getting some shaving of the exposed lead unless I seated the bullet deeper than mag length.
For some reason, the first round tended to hit slightly high and right compared to subsequent rounds. The only thing I could figure is that a manually loaded 1st round for some reason doesn't chamber the same as subsequent rounds. It wasn't much, but it was noticeable and repeatable.
I believe the gun is way over-gassed. The spent casings will go into the next county, even at the min powder charges. Maybe this would change if I used a faster burning powder (I intend to try H4198 sometime).
There is a company that specializes in upgrades for the Ruger Minis -
http://www.accuracysystemsinc.com/index.php# They have adjustable gas blocks and gas reduction bushings that I intend to try out.
Here is a good link as well:
https://loaddata.com/articles/PDF/BenchTopics 47 LR.pdf