or true lapping you have basically two alternatives: hand lapping and firelapping. The first normally uses a lapping slug on the end of a cleaning rod that is cast into the muzzle of the bore by plugging the bore back an inch or two with patches or paper and pouring molten lead into it. Grooves similar to lead bullet lube grooves are cut into the cast slug with a knife or a gouge to hold abrasive compound. The lap is loaded (the grooves filled) with abrasive and run back and forth in the bore by hand. It's s common to use something like 320 grit silicone carbide lapping compound (Clover compound, for example). The slug is usually pure lead so that when it encounters a constriction it is narrowed and does not spring back out after passing through it. In this way all abrading on subsequent strokes is only in the tight spots. When you feel it stop cutting tight spots, you can bump the lap back up with a brass rod and hammer, and go at it some
more. You keep repeating until the bore has no more tight spots and the lap feels smooth down the length of the bore.
"It is the soldier, not the reporter who has given us the freedom of the press. It is the soldier, not the poet, who has given us the freedom of speech. It is the soldier, not the campus organizer, who gives us the freedom to demonstrate. It is the soldier who salutes the flag, who serves beneath the flag, and whose coffin is draped by the flag, who allows the protester to burn the flag." -unknown-