I agree with karsten. And unfortunatly it is because the way they are built that there is slight inaccuracy. It has to do with the way the gas block and side block strike. read below for better explanation.
I have trouble getting any accuracy using the peepsights at 100 yards.After i whip on a 3x9x40 i get much better results.Wish they made see thru rings though.
I agree with the rest of the folks. The Mini 14 was never really known for super accuracy in its factory configuration.
If you got one of the new custom bull barrels installed on your Mini 14 it would definitely be worth the time. Otherwise I would expect good service grade accuracy and nothing more.
Another thing to remember is that if you fire lap with the Tubb kit it will help in the clean up too. It makes the barrel alot smoother so that it won't pick up as much copper. It can't hurt the accuracy either. For 28.95+shipping it's worth a shot. I'm going to try it on my 300WM and have read multiple articles about how good it works.