Damaged pistol crown question?

Eric Larsen · October 26, 2002, 02:05 PM

Ive run across a gun that has a damaged crown. It looks like it fell on a tiny flat blade screwdriver just as the crown ends and the bore is. It made a protrusion on a rifling and the edge of the bore, forcing the steel inside of the bore line. Its not very big..the protrusion is about .025-.030" inside of the bore line.
What will this do to accuracy and what if someone tried to fix it..taking out not enough metal or possibly too much.
I understand it will effect accuracy but in what way?
The gun would have to be recrowned. What would a target crown do vs a standard crown? Thanks for you replies!

John Lawson · October 26, 2002, 02:40 PM

We can only guess what kind of a gun it is. In any event, don't try to re-crown it freehand; use the proper crowning tool with a true bore sized pilot or in a lathe using the proper crowning toolbit.
An upset concentricity (such as will happen if you try to even out only the damaged area) will result in unequal forces on the base of the bullet, gyration in flight and an increased shot group. Too light a cut will result in a continuation of the upsetting action of the protrusion. Too much (too deep) a cut will result in unequal pressure on the bullet's base and (depending upon the bullet design) boat tail, also causing accuracy problems. A crown must be very precisely cut with a cutter equipped with a proper size pilot.
OK, people on safari have re-crowned a barrel with a pocket knife and saved the hunting trip, but the end result depands on what kind of accuracy you must absolutely have and the kind of tooling used...and perhaps the skill of the gunsmith.
If you are up against it and absolutely have to use an expedient, place a piece of 320 grit Wetordry abrasive paper over the muzzle, press a suitably sized ball bearing (approximately the size of the muzzle) into the end and twist paper and bearing uniformly with moderate but constant inward pressure. Finish with 600 grit and perhaps a different size of bearing ball. It should restore accuracy until you can obtain proper tooling.

ACTIONS BY R.A.K. · October 27, 2002, 01:00 PM

Eric,
your local smith should beable to take care of this, it a fairly common job, should run you approx $30.00 to $40.00, depending .

RON KONTOWSKY
ACTIONS BY R.A.K.

October 26, 2002, 02:05 PM	#1
Eric Larsen Senior Member Join Date: December 5, 2001 Location: Bountiful....Ut. Posts: 3,226	Damaged pistol crown question? Ive run across a gun that has a damaged crown. It looks like it fell on a tiny flat blade screwdriver just as the crown ends and the bore is. It made a protrusion on a rifling and the edge of the bore, forcing the steel inside of the bore line. Its not very big..the protrusion is about .025-.030" inside of the bore line. What will this do to accuracy and what if someone tried to fix it..taking out not enough metal or possibly too much. I understand it will effect accuracy but in what way? The gun would have to be recrowned. What would a target crown do vs a standard crown? Thanks for you replies! __________________ If they dont know you have a gun.....then I did alright! If you choose not to decide, you still have made a choice......Rush

October 26, 2002, 02:40 PM	#2
John Lawson Senior Member Join Date: August 28, 1999 Posts: 281	We can only guess what kind of a gun it is. In any event, don't try to re-crown it freehand; use the proper crowning tool with a true bore sized pilot or in a lathe using the proper crowning toolbit. An upset concentricity (such as will happen if you try to even out only the damaged area) will result in unequal forces on the base of the bullet, gyration in flight and an increased shot group. Too light a cut will result in a continuation of the upsetting action of the protrusion. Too much (too deep) a cut will result in unequal pressure on the bullet's base and (depending upon the bullet design) boat tail, also causing accuracy problems. A crown must be very precisely cut with a cutter equipped with a proper size pilot. OK, people on safari have re-crowned a barrel with a pocket knife and saved the hunting trip, but the end result depands on what kind of accuracy you must absolutely have and the kind of tooling used...and perhaps the skill of the gunsmith. If you are up against it and absolutely have to use an expedient, place a piece of 320 grit Wetordry abrasive paper over the muzzle, press a suitably sized ball bearing (approximately the size of the muzzle) into the end and twist paper and bearing uniformly with moderate but constant inward pressure. Finish with 600 grit and perhaps a different size of bearing ball. It should restore accuracy until you can obtain proper tooling. __________________ "Politicians are bilgewater in the ship of state."

October 27, 2002, 01:00 PM	#3
ACTIONS BY R.A.K. Junior Member Join Date: October 19, 2002 Location: MACOMB, MICHIGAN Posts: 11	Eric, your local smith should beable to take care of this, it a fairly common job, should run you approx $30.00 to $40.00, depending . RON KONTOWSKY ACTIONS BY R.A.K. __________________ ACTIONS BY R.A.K. CUSTOM PISTOLSMITHING CUSTOM GUNSMITHING DEANS GUNSHOP 2 1-586-716-3460