The Firing Line Forums - View Single Post - Concerned about some extra copper on the rifling near the crown

Bart B. · January 5, 2013, 09:10 AM

Regarding copper wash at the muzzle, either on the lands or in the grooves, that happens 'cause the bullet's jacket touches that area when they go out the barrel. It's common with most factory rifles. It builds up from any bore surface that's rough enough to scrape jacket material off bullets, but usually is not a problem

If there's no copper wash seen at the muzzle, it's due to at least one of two reasons. First, the bore's been intentionally lapped smooth and dimensionally uniform to .0001" or less by its maker so no bullet jacket material gets rubbed off; typical of best quality match barrels. Second, the muzzle area's bore and groove diameters have been accidently lapped to bigger numbers if there is copper wash visible back a ways in the barrel from cleaning with a rod without a bore guide. Rough steel rods and all aluminum or brass cleaning rods especially.

Having worn out 4 Garand barrels made at Springfield Armory in MA, they all started out with a bit of copper wash in the grooves and on the lands at the muzzle when new. After a thousand rounds and frequent cleaning with a solid, one-piece military steel cleaning rod polished very smooth, those surfaces were worn down (diameters enlarged) a bit so no more copper wash was seen the last 1/8th inch of the barrel. I never used a bore guide on the muzzle to protect the rifling. The worn area increased about 1/8 inch or more for every thousand rounds and at 5000 rounds, there was no copper wash for the last 5/8 to 3/4 inch or more. Others on military rifle teams report the same findings. It's normal and does not seem to effect accuracy.

January 5, 2013, 09:10 AM	#22
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Regarding copper wash at the muzzle, either on the lands or in the grooves, that happens 'cause the bullet's jacket touches that area when they go out the barrel. It's common with most factory rifles. It builds up from any bore surface that's rough enough to scrape jacket material off bullets, but usually is not a problem If there's no copper wash seen at the muzzle, it's due to at least one of two reasons. First, the bore's been intentionally lapped smooth and dimensionally uniform to .0001" or less by its maker so no bullet jacket material gets rubbed off; typical of best quality match barrels. Second, the muzzle area's bore and groove diameters have been accidently lapped to bigger numbers if there is copper wash visible back a ways in the barrel from cleaning with a rod without a bore guide. Rough steel rods and all aluminum or brass cleaning rods especially. Having worn out 4 Garand barrels made at Springfield Armory in MA, they all started out with a bit of copper wash in the grooves and on the lands at the muzzle when new. After a thousand rounds and frequent cleaning with a solid, one-piece military steel cleaning rod polished very smooth, those surfaces were worn down (diameters enlarged) a bit so no more copper wash was seen the last 1/8th inch of the barrel. I never used a bore guide on the muzzle to protect the rifling. The worn area increased about 1/8 inch or more for every thousand rounds and at 5000 rounds, there was no copper wash for the last 5/8 to 3/4 inch or more. Others on military rifle teams report the same findings. It's normal and does not seem to effect accuracy. Last edited by Bart B.; January 5, 2013 at 09:20 AM.