depends on how your rifle is setup and what you use for ammo.
as rip van winkle said, start with a free-float tube and good barrel combo.
A nice fixed stock will do wonders for check weld as well. It's about repeatability. Even with junk 3 shot burst triggers, I have seen guys do amazing things with a stock M4 or M16 series service rifle with no modifications to it. All the way to 800 meters with it too. Easily staying in the X and 10 rings. These guys wear the President's 100 patch for a reason too.