Repairing muzzle crown
- Thread starter cwalker3
- Start date
Precision Shooting has a book "Accurizing the Factory Rifle" that has quite a bit of home gunsmithing information including re-cutting and repairing a crown. One method they showed used a marble and 600 grit lapping compound. You put the lapping compound on the muzzle place the marble on top and roll it with your hand. Finish with cold blue.Obviously, the size of the marble should be carefully chosen.
The book also shows a method using a brass tool that chucks up in a drill to do the same thing. It also shows using a cutting tool with a pilot bit to completely recut the crown. Both of the following cost enough for the tools that if you only have one rifle to do, it would likely be cheaper to go to a professional gunsmith.
The "Accurizing the Factory Rifle" book can be ordered from Amazon. I recommend it highly if you like to tinker with your guns.
One thing about buggered up crowns on old military rifles: the damage is often done by cleaning the rifle from the muzzle without a guide and the wear can extend down into the barrel past the crown. Fixing this may require cutting a short bit off the barrel to get down to the good rifling then recutting the crown. Old Garands are famous for this.
The book also shows a method using a brass tool that chucks up in a drill to do the same thing. It also shows using a cutting tool with a pilot bit to completely recut the crown. Both of the following cost enough for the tools that if you only have one rifle to do, it would likely be cheaper to go to a professional gunsmith.
The "Accurizing the Factory Rifle" book can be ordered from Amazon. I recommend it highly if you like to tinker with your guns.
One thing about buggered up crowns on old military rifles: the damage is often done by cleaning the rifle from the muzzle without a guide and the wear can extend down into the barrel past the crown. Fixing this may require cutting a short bit off the barrel to get down to the good rifling then recutting the crown. Old Garands are famous for this.
I do it this way-
Use a round headed brass machine screw, 22's use about a #10 screw, 30 cal try a #12 or 1/4". Jam a tight oiled patch about 1/2" down the bore from the muzzle.
Get some fine valve lapping or rock polishing compound. It should be carborundum (sp?), and almost a fine as flour. Mine is 'fine' rock polishing stuff, it doesn't have a grit number. Get an eyedropper and a glass of water.
Hold the barrel vertical and fill the crown with compound. Use the eyedropper with water and add water until you get a 'slurry'. The patch should keep the slurry at the crown, you may have to keep adding water with the dropper.
Chuck the threaded part of the screw in a drill, and lightly spin the head of the screw against the crown of the barrel. The end of the screw should be in the slurry. Keep the drill pointing as straight down the barrel as you can. Check the crown every few seconds and note the progress. I think the best cutting action is with a light to moderate pressure on the screw. Keep the screw in the wet slurry when cutting. It may help to turn the rifle a bit everytime when you stop the drill for a more even cut.
Use a round headed brass machine screw, 22's use about a #10 screw, 30 cal try a #12 or 1/4". Jam a tight oiled patch about 1/2" down the bore from the muzzle.
Get some fine valve lapping or rock polishing compound. It should be carborundum (sp?), and almost a fine as flour. Mine is 'fine' rock polishing stuff, it doesn't have a grit number. Get an eyedropper and a glass of water.
Hold the barrel vertical and fill the crown with compound. Use the eyedropper with water and add water until you get a 'slurry'. The patch should keep the slurry at the crown, you may have to keep adding water with the dropper.
Chuck the threaded part of the screw in a drill, and lightly spin the head of the screw against the crown of the barrel. The end of the screw should be in the slurry. Keep the drill pointing as straight down the barrel as you can. Check the crown every few seconds and note the progress. I think the best cutting action is with a light to moderate pressure on the screw. Keep the screw in the wet slurry when cutting. It may help to turn the rifle a bit everytime when you stop the drill for a more even cut.
Hi, folks,
Proximo, cutting off the end of the M1 rifle barrel or counterboring it will usually result in malfunctions. The reason is that the gun must have gas pressure maintained for a minimum period to operate the piston, and cutting the barrel or counterboring will allow the gas to escape too soon. The rifle, as made, is very close to the minimum barrel length for reliable operation.
Jim
Proximo, cutting off the end of the M1 rifle barrel or counterboring it will usually result in malfunctions. The reason is that the gun must have gas pressure maintained for a minimum period to operate the piston, and cutting the barrel or counterboring will allow the gas to escape too soon. The rifle, as made, is very close to the minimum barrel length for reliable operation.
Jim
The method advise by ViKing is very simular to what I would suggest but the drill worries me. Power tools and guns don't usually mix. The patch, lapping compound and all is a good idea however. I would buy a steel ball bearing and do it by hand (steel bearing should fit the crown), spin the ball over the crown using a course lapping compound to a lighter grit. The Ball Bearing will fit the crown and spin to even the entire surface out evenly. Maybe more work but with a drill and a slight slip you will have a parts gun.
Hey, I do need a an operating rod
Karsten
Hey, I do need a an operating rod
Karsten
Yea, I should have said the drill goes pretty slow, maybe 200 rpm's or less. A fine grit, light pressure and slow speed won't cut much in a few seconds.
Every one I've done looked like it had been cut on a lathe and the corners and edges of the rifling were perfect.
When you said SKS I assumed it wasn't an heirloom quality collectable. If I had a custom stocked '47 model 70 .270 I wouldn't be doing this. I learned to do this after paying a 'gunsmith' to cut off a barrel crooked and screw up the crown.
Every one I've done looked like it had been cut on a lathe and the corners and edges of the rifling were perfect.
When you said SKS I assumed it wasn't an heirloom quality collectable. If I had a custom stocked '47 model 70 .270 I wouldn't be doing this. I learned to do this after paying a 'gunsmith' to cut off a barrel crooked and screw up the crown.
Please, ViKing.
No disrespect was intended. I for one couldn't do it your way without a lot of practice, meaning I would mess up at least once. The ball Bearing is just a safe, slower way with a bit more work. Then again I am sort of from the old school like hand rubbing 12 coats of tongue oil into a Norinco stock. It is very nice but it is still a Norinco wood stock.
No disrespect was intended. I for one couldn't do it your way without a lot of practice, meaning I would mess up at least once. The ball Bearing is just a safe, slower way with a bit more work. Then again I am sort of from the old school like hand rubbing 12 coats of tongue oil into a Norinco stock. It is very nice but it is still a Norinco wood stock.
I'll jump in late. I've used both the drill and marble approach. I preffer the drill if it's variable speed and you have the patients to go slow, otherwise use the elbow grease method. Phillips head screw works better for me than the slotted, more uniform contact with the crown. Good luck and don't get in a hurry, most of my home smith screwups are from getting rushed.
I've never seen a phillips, round head, brass machine screw. I never thought of that, I just assumed they were all slotted.
You can spin the screw in the drill against some SiC autobody paper to true up the screw head before you start.
I use a drill because I'm too lazy to do it by hand power, not because the drill is better.
You can spin the screw in the drill against some SiC autobody paper to true up the screw head before you start.
I use a drill because I'm too lazy to do it by hand power, not because the drill is better.
ViKing,
When you said round headed screw, I immediately thought "slotted." I thought the slot would also be effective in grabbing more compound. When you said electric drill, I'll bet you meant battery powered. It's surprising what delicate work can be done with a variable speed battery drill.
As you're stressing, it doesn't go all that fast. I'd certainly try it. For people wanting to use a steel ball, I'd suggest epoxying it to a stick and twirling it between thumb and forefinger. It seems to me that rolling it with your fingers or on your palm could lead to an elliptical crown.
When you said round headed screw, I immediately thought "slotted." I thought the slot would also be effective in grabbing more compound. When you said electric drill, I'll bet you meant battery powered. It's surprising what delicate work can be done with a variable speed battery drill.
As you're stressing, it doesn't go all that fast. I'd certainly try it. For people wanting to use a steel ball, I'd suggest epoxying it to a stick and twirling it between thumb and forefinger. It seems to me that rolling it with your fingers or on your palm could lead to an elliptical crown.
Karsten,
We're the same on refinishing cheap stocks. I sanded a stock Ruger 10/22 "hardwood" stock so that every nook and cranny is furniture quality. The wood is so hard it wouldn't take any stain I tried. I finally had to make my own by soaking walnuts in ammonia for a month. Finished in tung oil and got a metal buttplate for it. Are we nuts or what?
We're the same on refinishing cheap stocks. I sanded a stock Ruger 10/22 "hardwood" stock so that every nook and cranny is furniture quality. The wood is so hard it wouldn't take any stain I tried. I finally had to make my own by soaking walnuts in ammonia for a month. Finished in tung oil and got a metal buttplate for it. Are we nuts or what?