The Firing Line Forums - View Single Post - Re-crowning a cut barrel?

wpsdlrg · February 22, 2013, 07:05 PM

I've used a round ball (or similar shape) stone to rough in a crown on many cut barrels, over the years. After that, a round head brass bolt, of the appropriate size and contour, with valve grinding paste, to final contour and polish the crown.

This works very well, if a few rules are followed :

1) Make sure the stone used is concentric (doesn't wobble when spun in a drill). That is easy to check visually, of course. Buy a GOOD quality stone - it will be worth it. A medium to fine grit stone will do - skip the really rough grade stones.

2) The brass bolt WILL be concentric, in all cases, if it is of good quality. Again, check this visually, before use - don't use a non-concentric bolt. Also, size the bolt head to the barrel/ bore size. You really want a true half-round bolt head, in order to do a nice recessed crown, but that is up to you.

3) BE SURE to plug the barrel tightly, right up to the muzzle, to keep the valve grinding paste OUT of the barrel (and away from the rifling).

4) If the bore of the barrel is centred (concentric in the barrel), then the crown you create will automatically be concentric. Even if not, the crown WILL be concentric to the bore, which is what's most important.

5) BE SURE that the cut end of the barrel is SQUARE. USE an engineer's square, or other ACCURATE tool, to determine this. "Eyeballing it" is NOT good enough. If you start with a slanted cut, then the crown will be slanted - and the barrel won't shoot properly. THIS IS CRITICAL. If you screw this up - the rest is wasted effort !

6) GO SLOW. Take your time and be careful. If you take care to cut a good, clean rough crown with the stone, then the finished crown will almost certainly be good. If you scar the cr#p out of the end of your barrel, via ham-handed technique with the drill, then the end result will look like cr#p. Do a good job....and it will look "professional".

7) Polish the crown, using the bolt and grinding paste, thoroughly. The smoother, the better. Polish it until it shines like a mirror. That will eliminate almost all chance of leaving a small nick, which would affect accuracy.

February 22, 2013, 07:05 PM	#7
wpsdlrg Senior Member Join Date: August 18, 2009 Posts: 826	I've used a round ball (or similar shape) stone to rough in a crown on many cut barrels, over the years. After that, a round head brass bolt, of the appropriate size and contour, with valve grinding paste, to final contour and polish the crown. This works very well, if a few rules are followed : 1) Make sure the stone used is concentric (doesn't wobble when spun in a drill). That is easy to check visually, of course. Buy a GOOD quality stone - it will be worth it. A medium to fine grit stone will do - skip the really rough grade stones. 2) The brass bolt WILL be concentric, in all cases, if it is of good quality. Again, check this visually, before use - don't use a non-concentric bolt. Also, size the bolt head to the barrel/ bore size. You really want a true half-round bolt head, in order to do a nice recessed crown, but that is up to you. 3) BE SURE to plug the barrel tightly, right up to the muzzle, to keep the valve grinding paste OUT of the barrel (and away from the rifling). 4) If the bore of the barrel is centred (concentric in the barrel), then the crown you create will automatically be concentric. Even if not, the crown WILL be concentric to the bore, which is what's most important. 5) BE SURE that the cut end of the barrel is SQUARE. USE an engineer's square, or other ACCURATE tool, to determine this. "Eyeballing it" is NOT good enough. If you start with a slanted cut, then the crown will be slanted - and the barrel won't shoot properly. THIS IS CRITICAL. If you screw this up - the rest is wasted effort ! 6) GO SLOW. Take your time and be careful. If you take care to cut a good, clean rough crown with the stone, then the finished crown will almost certainly be good. If you scar the cr#p out of the end of your barrel, via ham-handed technique with the drill, then the end result will look like cr#p. Do a good job....and it will look "professional". 7) Polish the crown, using the bolt and grinding paste, thoroughly. The smoother, the better. Polish it until it shines like a mirror. That will eliminate almost all chance of leaving a small nick, which would affect accuracy.