Fire-lapping--or not...
I once bought a new Taurus .357 magnum revolver. The bbl leaded like crazy--after a shooting session I'd take it home and actually pick hunks of lead out of the rifling, and the ports, as a start on cleaning it. Was using it as a target pistol, and shooting nothing through it but lead wadcutter bullets.
This annoying tendency continued for some time--Until I got quite a few rounds through the revolver. Say 1500 rounds as a guess. Anyhow, at one point, the dreadful leading simply stopped, like closing a door. It never came back.
My surmise is that I had lapped the bbl, and removed the rough machining that was catching all that lead, only with lead bullets it took quite a few to do it.
Sure was nice to have it happen, though!
I suspect that that particular firearm would have benefitted from a Tubb Final Finish job.
I buy very few brand-new firearms, so most of what I have has been pre-broken in for me. This one revolver was an exception.