I have shot a ton of lead out of original Sharps and Trapdoors. I cast bullets at 20-1 and have tried 40-1. 40-1 is harder to get good full bullet mold fill-out. Trick is a soft lube. I am about out of a home-brew mix that my friend made. Bees wax, Murphy's oil soap, and a touch of graphite. After sizing and lubing, I set the bullets in the plastic pistol ammo trays to give the lube a chance to crust on the outside to make handling easier. I also prep barrels after cleaning with a couple of patches lubed with T/C 1000+. I find it also helps keep shotgun barrels free and clear of wad plastic. Especially true in my smooth bore Ithaca Deerslayer and Forster slugs.
Lead attracts more lead. Same for copper fouling. So best to start with a really clean bore. I have used this with good results, then clean bore with alcohol, then T/C 1000+. https://www.midwayusa.com/product/1014882435?pid=398676