Here's the thing...
If you want to shoot accurately at 200-300 yards, a semiauto just means extra cleaning, and a LOT of extra money to get the same accuracy as with a bolt action. You won't be shooting rapid fire at 300 yards.
Perhaps consider a smaller-caliber semiauto and a larger-caliber bolt action.
Mini-14 is a fun gun in a great package. But a 300 yard target rifle it's not. Hell, it's not much fun to punch paper at 100 yards with it, but reactive targets are always fun. And it's flat-out not worth the money Ruger now charges for it. I have one in stainless and xytel, and it's well worth keeping since I have it. But I wouldn't walk out and buy one again for $600+.
For that money, you can get a decent bolt action to shoot stuff 300 yards away, and an SKS or something to play with. Or, the newest version of the Kel-Tec SU-16 is nice, and it folds up for convenient storage.
Or, you can go with an AR, and have a gun that you can build out with several calibers, barrel lengths, etc., for little more than the price of a Mini these days.