When I was shooting cast bullet comp in the 80's with Elmer Shook, we used pure linotype, water quenched, heat treated, with gas checks. 308 Winchester caliber and Hart SS Barrels we shot cast bullets in never saw a copper jacket bullet...never.
Undersize bullets will deposit a lot of lead vapor in the barrel, and a .0005-.0015 is a very good thing on the bullet dia.over size...know the bore dia of your barrel.
Cleaning with bronze bristle brushes with FINE Bronze wool wound in the bristles is needed from time to time to remove the lead.
For commercial vendor, check out GT bullets in Ga. George is an avid cast bullet shooter in pistols and rilfes and will alter his mix and sizing Dia for your needs.
I ordered George's HP with a soft alloy mix in the
9mm 130g hp- expanded to 69 caliber
40g-180g HP expanded to 85 caliber
45 200g hp expanded to 95 caliber
http://www.gtbullets.com/
