PDA

View Full Version : Polishing a Chamber



Poygan
10-26-2010, 08:38 PM
I put some scratches in the chamber of my M-1 carbine while removing a case when the head separated. More cosmetic than anything but I'd like to clean it up without doing more damage. The damaged area is about 1/4" into the chamber. Appreciate any suggestions, especially if they are feasible for the mechanically challenged.

looseprojectile
10-27-2010, 04:53 AM
I believe you are since you scratched the chamber to start with.

Enough of that.:redneck:

Find someone to drill and tap a fired case from your rifle. It would have to have the same thread as the male thread on a cleaning rod. With the primer pocket so drilled and tapped thread the case on the rod after inserting the rod in the muzzel end and add a very little fine valve grinding compound to the back half of the case and turn it with a drill motor and pull toward the muzzle a little.
Shouldn't take much. Unless you really get carried away it would be hard to screw it up. And back off of your loads. I have never seen a carbine bust a case.
Those are tough little suckers.

Life is good

Mk42gunner
10-27-2010, 04:14 PM
Looseprojectile has the right idea, but.. I would use something a lot finer than valve grinding compound.

Roy Dunlap recommended using jeweler's rouge, I believe. You really don't want anything course enough to put grooves around the chamber.

Robert

Poygan
10-27-2010, 08:06 PM
I have some 600 grit for fire lapping. Is that fine enough?

Mk42gunner
10-28-2010, 12:32 AM
Poygan,

I'd really like to give you a definitive answer; but it would be a case of the blind leading the blind, since I haven't had to polish a chamber before.

That said, 600 grit still sounds awful rough to me, I have some 800 grit to lap scope rings with and it will remove a lot of steel from a set of Leupold rings very quickly. The block of jeweler's rouge that I have almost feels smooth when you runyour finger across it. (I use it for the final honing of a knife blade, on a piece of leather).

You said it was cosmetic mainly, will fired cases extract now? If so, I might be tempted to try spinning a bare case first.

Another thought. Instead of trying to find a tap to match the thread of a cleaning rod, what about cutting some 1/4-28 threads on a piece of 1/4" drill rod then chucking that in your drill?

Robert

looseprojectile
10-28-2010, 03:30 AM
600 grit would be fine, finer than I have ever used and I have done fine. Use just a touch. An application of a very thin coat of some kind of grease will hold the grit on the brass.
Most any grinding compound is self reducing. That means that as you use it it breaks down to finer particles. Be careful as you first introduce the gritty case, you can't expect it to fully enter the chamber. It will tend to stick if you are not on the ball.
In this instance the grit will embed itself in the brass and nearly quit cutting after a short time due to breaking down to smaller particles and filling with the steel it is cutting out of the barrel.
Probably won't take ten or fifteen seconds of turning the case in the chamber.
A little compound spun in the chamber wont make grooves in a chamber it removes them. The technique would be to keep the spinning case moving in and out a little as you turn it. Good luck!

Life is good

Poygan
11-02-2010, 12:23 PM
I appreciate the ideas guys. Here is what I did. I took a fired case and cleaned the inside. Next I filled it with JB Weld and put in a .22 bronze brush. After a day or two of curing, I put the case and brush combo into the chamber and put an aluminum cleaning rod through the muzzle and threaded it into the cleaning brush male end. Applied a bit of the 600 grit (which is already in a grease type base) onto the case and spun it carefully in the chamber with a variable speed drill.

At the range i blackened several cases to see the scratch marks or the lack thereof more easily. Seems to have worked to at least minimizing the scratching of the cases. Yes, it did eject reliably before but I didn't like the damage however minor to the cases.

Just1Mor
12-10-2010, 03:24 PM
i have read several of the old gunsmithing books and they all talk about using fine emery cloth to finish a chamber. I have a grand/bm59 that was pretty rough and that is what i used and worked like a charm. But the action was hardend by a pro and is tougher than the older garand so it will take more of a pounding if the case does not grab the chamber walls good.

Just1Mor
12-10-2010, 03:25 PM
sorry, i think i used 1200 grit.