My new Winchester Model 70 .375 tends to copper foul a lot, so I asked Mark Penrod what to do (he's the one who got it to feed correctly after the factory ****-ups).



He said to shoot one or two shots, clean thoroughly with Sweets until the copper is gone, then use a tight jag with JB Bore Cleaning Paste and and a bore guide; run the patch breech to muzzle just a few times. Repeat shooting as necessary (about 60 times!).



If you don't like cleaning the gun after every shot, you can fire more for practice, sighting, etc but they won't be polishing the bore because the rough spots are already coated with copper after the first shot.

Any ideas? Thanx

I have done it, and got bad reults.
I prefer to buy them handlapped at the factory.

This isn't something the average person can do.

It requires removing the barrel, using a lead lap impregnated with abrasive, and time and muscle.

Fire-lapping is a possiblity, but it will erode the throat somewhat.

Worried about your new rifle?

George

Yup. I wanted a smooth barrel for TSX and other Barnes bullets use.

Buy a cheap barrel blank. I have done several Numrich 45-70 barrels. Cast your laps on long machine screws that are centered in the bore with a rubber grommit or string windings. Use a guide at the breach end so the rod does not rub. I cast my laps from alloyed lead, they seem to last longer. Oil the bore and work the clean lap to be sure it moves all the way back and forth. At this point add a small amount to valve grinding compound. I start with "coarse" clover compound. I know some will advocate the kind that breaks down. I am removing some significant steel and it takes too long as is. OK, keep it very oily and work it full length. The Numrich barrels are garbage quality so you can't hurt much. Once the lap gets pretty free add some more grit. It will be tight again, work it some more. Once it won't tighten up from more grit clean the bore and take a look. It will still have the toolmarks. Cast another lap and repeat. Once it is uniform and the toolmarks are gone, or you get tired and fed up, go ahead with putting a choke in it. Do not lap the muzzle anymore and concentrate on the main part of the tube. I prefer a little choke in muzzleloader and cast bullet barrels, which is what I am talking about. Once you can feel the choke go ahead and make another lap and lap with 220. Make another lap and use 320. When the finer laps are "worn out" give the muzzle section some working over. You may want to drill a hole down the center of the lap and insert a tapered wood screw to expand it and make it tight in the section behind the ckoke. This will save casting so many laps. Anyway, when you are done, polish with semichrome or flitz and steel wool as a final step. This whole project will take several hours.

I know many are going to say I have ruined the barrel. I have not found this to be true. In larger bores and with cast bullets this produces a straight shooting rifle that cleans up very quickly. I would not do this with a good quality barrel or a a small bore. I have only done 45 caliber barrels. The lapping rod is large and does not tend to bend and rub. My last one was a numrich barrel with a nasty gouge out of one of the lands and a very rough finish. It shoots really well, about 2" at 100 yards with black powder and pure lead bullets. It is on a rolling block carbine.

I have never attemped to lap a chambered barrel. I think you would just make a mess of things if you did.

"Yup. I wanted a smooth barrel for TSX and other Barnes bullets use."

If I could afford to buy a decent barrel I would do that. Trying to make a rough barrel into a good one is going to be an uphill battle. As far as lapping for a hunting rifle, I would forget it. Maybe shoot some of those NECO or other grit bullets down it, like others suggested, but, that is about all I would do. I know others will scream bloody murder at this.........I have shot cast bullets that were rolled in valve grinding compound. Did it many years ago before anyone knew what NECO was. It works. Make sure the bullets are larger than bore siameter and preferable throat diameter. Roll the lubed cast bullet on steel plates with the grit. I have used two old files. Breech seat the bullet. Use a case less the neck potion loaded with a minimal charge of shotgun or pistol powder. Shoot several. The barrel will smooth up and develop a taper. We made some pretty trashy barrels shoot cast bullet very well. The only one I ever shot after with jacketed bullets was a M-1894 Winchester rifle in 30-30. It was badly pitted, still is. It shoots far better than it had any right to with jacketed. Can't say it is proof of the process. It did work for me.

This home lapping thing I described is more because I enjoy doing such work. The last rolling block was a $45 Ejyptian and a cheapo barrel blank. I made all new wood and furniture, the barrel was a blank I lapped, turned, threaded and chambered. The action was so bad that initial trueing and pit removal was done on a belt sander. Sights are period from a Springfield, I think. Made it like the baby carbines. I probably have about $120 in the whole thing. It is a cutie and shoots great.

I've hand lapped a sack full of revolvers with excellent results, every time.
I learned how to do it reading LBT's little blue book on cast bullets. The book costs $10.00 $12.00.
Read this technique and see if you wish to pursue the project.
Jim

I suspect from his posts that Bill Leeper is a great professional gunsmith.

If you are like me, an amateur who screws up everything, lapping is not easy.

At least with glass bedding, after I got it all over me and the floor, I could chisel out the stock and try again. But the bores I wreck are not going to get another chance.