I recently acquired a used S&W HB M10, like new. It was one of them made by Bangor Punta. Its only defects are that the hammer drags on one side, which is fixable, and the barrel is constricted at the point where it goes through the frame. The barrel constriction results from over tightening the barrel, of course.

Most dyed-in-the-wool pistolsmith recommendations are to replace the barrel. My question is: Would lapping the constriction out be satisfactory? I am not familiar with anyone who has done that, and what kind of results they got.
TIA.

I'll bite. My 44 mag was like this. Wouldn't shoot lead worth a hoot, and fouled badly with lead.



I lapped the bore with a poured lead lap, as described by many sources. Started with 220 grit. The lap would not last long due to the swaged section making it smaller, so I had to "bump" it often. Stay with 220 grit until the swaged section is out of it. Only work the swaged section, coming out the cylinder end of the barrel to load the lap.



I think this is described well in the LBT handbook, IIRC. Maybe check the Beartooth bullets site for more lead bullet shooters.



Mine got a bit better. I think (at least my) lead bullets are just not as accurate as jacketed factory rounds. Fun to shoot, though. The fouling did stop.

I did this by fire-lapping with a LBT kit on a S&W M25-5. It was noticably tight under the threads and groups were poor. Groups improved by about 1/3.

Just remember that for fire-lapping you want to use pure lead bullets (normally you have alloy bullets) The pure lead bullets are soft and won't "spring back" after they pass the bulge, thus they wear only where you want it.



LBT and Beartooth books both get into this subject. I think Beartooth sells the soft lead bullets for measuring barrel dimensions. I seem to remember that one thing to avoid is using carbide grits as they can embed into the bore walls. You need to use a non-embedding abrasive. I'm not sure, but I think garnet might be the right stuff.



LBT was out of business except for books. Anybody know if they're back in business?

Just ordered a Clark slab-sided barrel from Brownell's and will fit it asap. Not enuff info to trust a second-rate barrel, I guess. Thanks to all.

Pure lead works fine for lapping bullets but takes a very long time. IIRC Veral Smith recommends bullets of about 12 BHN to be about right.

I bought one of the LBT lapping kits and have successfully lapped about 4-5 revolvers and ruined one.

The one I ruined was the first I tried because I overdid it - you know, if a little is good, a lot is better... Turned a decent shooting Ruger .357 Blackhawk into a short barreled scattergun

But once that lesson was learned every single one of the others showed a very noticable gain in accuracy (with cast bullets) and a lesser tendency to lead.

LBT is indeed back in business - you can order a catalog or whatever else you need here:
http://www.leverguns.com/lbt/index.htm

I hold the opinion that all of this concern about constrictions caused by screwing the barrel into the frame is very over rated. I have never seen a revolver that didn't have some level of constriction and most shoot very, very well. In most cases you can't see it. Chronic leading problems caused by a rough forcing cone or a rough barrel can be cured without lapping. The forcing cone can be recut to removed the "wash board" tool marks. Barrels can be polished to remove the roughtness there. A sixgun with a smooth forcing cone and polished bore will not lead and be very easy to clean. I have a K-38 that was a chronic leader, but after polishing the bore, does not lead a spec. With a high polish bore, the constrictions at the breech end are highly visable, but they do not degrade the accuracy or cause leading by themselves. Here is how I polish:

I fire 200 rounds of jacketed ammo as fast as I can load and fire. I then open the cylinder and with a new bronze brush and solvent scrub the bore with 200 fore and aft passes. You will need to wear gloves as the pistol will be very hot. These 200 rounds will take out any small burrs or wire edges.

At home, I clamp the pistol in a vise and with tight fitting patches and a metal polish like Semi-chrome, polish the bore for a full hour or until my arms feel like they will fall off.

At the end of this process you will have a smooth mirror bore that will not lead and cleans very easy. No significant amount of metal is removed and none of the dimensions are changed.

If you are going to recut the forcing cone, do it before the firing and polishing.