Please excuse my ignorance, but if I don't ask, then I won't learn. Many of the top gunsmiths state that most barrels have a "crooked" bore and they machine it so that the bore is at the 12 o'clock position when the chambering is completed. What is the best way to do this? Can one use a range rod in the muzzle and mark the barrel with a sharpie? Should one also check the breech end. Thanks in advance for any input. James