Google Search: lapping group:alt.sport.air-guns group:alt.sport.air-guns: "Mitch wrote

>How bad is the crown now? Do you need to cut the barrel back a bit, or can

>you just lap

>the existing crown?

>You may be able to recrown without pulling the sight, get some fine lapping

>compound such

>as JB Bore Paste, and a brass round-head screw with a head a

>bit bigger than the bore. Chuck the screw in a hand held drill, goop it up

>with Bore Paste, and rock the drill back and forth as it turns, frequently

>stopping to turn the barrel a bit. When you've polished an even margin all

>around, clean the barrel and test-fire. Most of the plastic sights are

>pressed

>on, you can usually heat them and tap them off. The trick with cutting back

>the barrel is

>to get the face square to the bore, not an easy task with hand tools.

>A good machinist can probably file it square after cutting, but I can't."