Would 45 acp have a low enough pressure to fire pure lead without problems? I couldn't imagine doing so in 9mm.
Back about 30 years ago I shot some combat type of shooting at an indoor range with my 45. The ammo I was loading was zero bullets that were 200 grain swaged lead. Back then, zero only made pure lead swaged bullets. They had a funky dry wax coating that worked for about 200 rounds, starting with a clean barrel. After 200, the barrel would start building leading.
I once took a bunch of those swaged lead bullets, spread them on a newspaper, sprayed them with pure silicone. They were so slippery, I could barely pick them up. BUT they stopped leading!
A cast lead pure boolit, should be lubed with a good quality boolit lube. Then, if they fit your bore, you should be able to shoot quite a few before leading begins.