The faster you push LSWC the more lead you leave in the barrel.
Not true at all. That's a myth. I've pushed lead SWC bullets in my .44Mag from 700-1300fps with no leading what-so-ever. I am sure I could push even higher (just haven't found the need to do so). BTW, all I shoot is lead in .357, 44Spec/.44Mag, and .45ACP, and .45 Colt. If throats are wrong size... you will lead. If you have barrel constrictions you will lead. If you have wrong hardness of bullet you will lead. There are many reasons for leading.... But velocity isn't one of them