RE: mini 14/30
I'll now introduce you to the real meanings of accuracy and precision.
Check out a dictionary sometime....When we say "accurate", we typically mean "precise"--> look it up.
Accuracy is how close you are to the bullseye. Basically, if the center of your group is centered on the target, you're shooting "accurately".
Precision is how close your shots are to eachother. If your groups are very small, your rifle has high repeatability and is very "precise".
Any gun, given the proper amount of sight adjustment can be made to shoot "accurately". Accuracy has nothing to do with group size in it's raw definition. If the group is centered on the bullseye, your gun is accurate...move your sights far enough and shoot a big enough target and you'll be able to center a 10ft group on the bullseye.
Precision shooting, on the other hand, is shooting small groups. I can make ANY gun accurate just with sight adjustments, I cannot, make a gun more precise by adjusting the sights (sighting in).
It's kind of a misnomer when people say they have an "accurate" rifle. Like I said, I can make any gun accurate, they have a "precise" rifle that they've sighted in, making it both accurate and precise.
When your rifle was off by a few inches, it was inaccurate, it deviated from the "true" value, it deviated from the bullseye...But, sighting it in only moved your point of aim. It changed nothing about where the bullet is headed after it leaves the muzzle.
Mini-14's can be made to shoot their big groups centered on the bullseye-any gun can be made accurate by sighting it in.
However, they're still going to shoot big "Imprecise" groups...fixing this takes a bit of money. Like others have mentioned, it's usually better to just buy an AR-15 than to try your luck with a Mini (and I'm one of the biggest Ruger fans you'll meet!)
If you're looking for a 30cal, then an SKS can be had for about 1/3 the cost of a mini-30, and like briman mentioned, it'll do everything the mini-30 can do just as "inaccurately".
Some SKS's are quite accurate though. I'd also venture that you could find a CETME .308win (7.62NATO) for cheaper than a Mini-30 that would have a lot more power and be more accurate...I bought my current CETME for $250, it shoots very well, I just wish I could find a good scope mount for it.