I regularly shoot PB boolits out of my 45-70 revolver at over 1600 fps with great accuracy and no leading.
All of my .475 and .500 boolits are PB. some of my .45 Colt boolits are PB.
I just water drop WW boolits, 20 to 22 BHN. They do not slump in the guns and do not deform after going through 16" of seasoned oak.
I have shot PB from a .454 to 55,000 psi with very good accuracy.
The gas check is to stop skid at the base band so you don't lose the gas seal. Make the boolits hard enough to do the same and they are good.
I quit making my molds for gas checks since it is cheaper to use gold leaf at those stupid prices.