SWC MidBand, Leading

[phigaro4570]

Recently I lapped my .44-250-K rear driving band to try to remedy the leading I was getting in the cylinder and forcing cone. I have never heard the middle and front bands mentioned much, but I have come to believe that, before the rear band makes it to the cylinder throat to seal there, gasses shoot past the mid-band before it gets to the throat. So, I lapped the mid-band out another .001" and, now paranoia is creeping in and I really wish the front band were .432" as well. At least it would be doable on the RCBS, but my Lyman 358429 has a front band that is around .004" small. I haven't yet tried shooting since the mid-band is larger, and don't know if I will end up wanting the front one larger, too. (That one would really caulk the hole quickly.)

Perhaps I don't see these bands mentioned specifically because people are enlarging or beagling the whole cavity uniformly. I drove a 5/32" Allen wrench in the same sized hole and got enlargement only on the rear most piece of linotype bullet I was using. Has anyone else pursued this same trail with a SWC and leading? I guess you'd encounter this same problem relying on obduration since it would presumably affect only the rear band.

Thanks,
Phigaro4570

[btroj]

Front band matters. It isn't just to prevent leading. The front band is the first to engage the rifling. It needs to be full diameter to properly grab and hold the rifling, failure to do so can tend to allow stripping and skidding.