If your rifle is shooting good and the patches it throws are not torn up or damaged, I really think lapping the barrel would do you no good. Lapping is the removal of metal from inside the bore. It is not something you do unless you really have to.

Many new rifle barrels are ruff. A quick lapp job will often times bring them around. One way to lapp a rifle is to shoot the ruff spots out of the gun. Unless your rifle is pitted and rusted in the bore lapping is not the answer. It might even make the rifle less accurate. And once you remove the metal from the barrel you can not put it back......