As I have posted many times, it is easy to fix the problems with the Mini-14s accuracy. It just takes some nerve to be willing to disassemble the gas block.
Just get a RCBS hex wrench set. The largest wrench fits the gas block. Disassemble the rifle as per the Ruger instructions. Unscrew all the screws on the gas block (don't be supprised if several of them are not tight). Clean off the gas block with a good gun scrubber. Look for any burrs. Take them off with some light file or cauccus cloth.
When reassembleing, just hand tighten all the 4 screws (clean them off first and put a little lock-tite in them). Get a car feeler guage (for spark plugs). Now, just like a car tire, jump around tightning the screws just a bit. Check the gap between the high and low gas block plates that fit on the barrel. Make sure they stay even all the way around (this IS the problem, uneven pressure). After all the screws are tightened and the plates are even, let the lock-tite set for 24 hours.
If you want to go further, get some Acra-glass and glass bed the two metal reinforcements INTO the stock. Yep, that makes a real stiff stock.
Then, the last minimum thing I can think of doing is getting rid of the wiggleing rear sight. That sight is worthless. Eagle makes a polyimer rear peep that replaces the metal 'L'. Get it, and fit it to the slot (might need just a bit of filing). I drilled the apendature just a bit larger myself.
Ok, then get some good 64 grain ammo and try from a bench. I got 1 inch groups at 50 yards (NO cooling of the barrel, just 3 good shots). That gun can stay in a 4 inch group at 100 yards, 10 shots strait, no cooling of the barrel. Good enough!
Now, if you do this yourself, very little cost. If you have a gunsmith, go get a AR... you will be spending 200 bucks, hell, get the AR (I have both!!).
Deaf