Lyman has a book dedicated to casting, and their regular re-loading book has a chapter that is very helpful.
Originally Posted by carver
It's been my experience that any lead bullet moving at over 750 fps will lead the heck out of the barrel. All that powder burning behind that lead bullet will melt it and leave horrible deposits of lead in the lands and groves.
I regularly shoot plain based lead bullets over 1200 fps in a handgun, and gas checked bullets over 2700 fps in a rifle.
Lead is only deposited in the bore for two reasons.
1. improper lubrication. The lube needs to be soft enough to lubricate, if it looks like crayon wax, all it's good for is coloring pictures.
2. undersized bullets. If the bullet is too small to swage into the the lands and grooves of your barrel, the gasses behind the bullet will leak past the bullet, and "cut/melt" the lead like and acetylene torch cuts steel.
Shotgun loads are shot in excess of 1200 fps, and if the powders/gasses don't melt the PLASTIC wads and hulls, how can it melt lead?