lead chucker if your bullets are .357 and you are using virtually any commercial or home made lube and your velocities are around 1,100 fps. then there is no reason for your guns to be leading unless you are using pure lead. That would seem to be the only variable. It isn't the barrels because you are getting leading in all your pistols not just one.
Casting God is not the type to pick on just one of us. Usually it is all of us or nobody. Your situation defies logic. I am out of answers.
Take Care
Bob