DON'T TRY THIS AT HOME...but in this case I thought it couldn't hurt.
A friend of mine bought a Huntsman 2 years ago. We shoot and hunt together. It got 2"+ groups for him at 50 yards. This fall he told me that another friend never cleaned his MLs after he fouled them, until the end of the hunting season. He decided to try it...except he cheated part way though - once. I told him that that was bad advice, and cleaned mine every day. At the end of the season he told me that he was having a hard time 'getting his barrel clean.' Uh-oh. He showed me and upon using a magnifying glass and getting the light right you could see pin-head sized dimples. He was so disgusted that he sold me the gun - which I bought for the receiver, etc.. Two days ago I thought, why not lap the barrel to death and see what happens? If I couldn't get it cleaned maybe I could ream it into a ML shotgun? Rubbing compound with a bore brush cleaned the barrel, but didn't touch the pits. So I went to my rock tumbling compounds and started adding 200-300 silica carbide grit to my 'loaded' brush. Did that for 1/2 hour. Kept cleaning and checking, expecting to see the lands worn or not as crisp. But slowly the pits were becoming not as apparent...back and forth, back and forth and the lands not so bad. Switched to 400/600 silica carbide and went with this for almost 2 hours - slowly - carefully - from the breach end. Kept checking. Felt like sand-paper going through the bore. I was like a demon adding more and more grit! Then I switched to aluminum oxide pre-polish, and finally the rubbing compound. About 4 hours of work. The brush was able to rotate with the rifling. And it does look like some of the rifling at the breech was worn. But 1/2 way up the barrel to the muzzel it was hardly worn at all. Wish I could send you a pic of the inside of that bore! SHINY!!!
Went and shot it yesterday. Put 30 rounds through it. It cleaned up brand new with water and soap. Here's the proof of what it's doing at 50 yards - 2, 3-shot groups. Haven't told my friend yet, but I think I now have a mighty fine little gun...bit o muscle was all it cost.
Hey, now don't go doin' nuthin stupid like wrapping sandpaper around your cleaning jag to accurize your ML - I just figured that I had nothin' to loose.
Last nite I machined a set of iron sights onto it from a .45-70 Handi that were laying around - put a peep in the rear Williams sight - and does it point nice! Shoots as good as any other ML I have - maybe better?
Time will tell.
All the best -
doc