The reality is, unless you go to the trouble of getting cast bullets of appropriate size and hardness for your gun and powder, you'll get leading. Even a good combo will lead a little.
I recently went to coated cast (MBC HiTek, Bayou, Blue Bullets) and will likely never buy plain cast bullets again, and have cut way down on what I buy for plated. No leading, no copper fouling, and the reduced powder charge that goes with shooting cast lead. Best of all worlds.
I do like the MBC cast 185 SWCs in .45 and have a great bullseye load for them that I haven't yet been able to replicate with the Coated bullets I've tried yet, but I'm more likely to continue trying than I am to buy another box of plain cast lead bullets.