Hard cast bullets will help unless you are really, really pushing them fast. Then, you may be actually melting the base of the bullet as it is going down the barrel. If that's the case, you need to go to a gas checked bullet.
For normal lead build up, get a Lewis Lead Remover. It will clean normal build up out fast. Every CAS shooter that uses them swears by them (and CAS shooters MUST use only lead bullets in competition, so they shoot a lot of them).
For a heavily leaded barrel (like a S&W 1917 I bought once), the Outter's Foul Out system works wonders. I think it's up to the 4th incarnation now, but my Foul Out III cleaned the bore down to bare steel in about 3 sessions. It kinda works like electroplating- but in reverse. It draws the lead (or copper, depending on the solution you use) to the electrode you put in the barrel. It ain't cheap but you don't have to worry about scrubbing lead build up.