Actually, gun barrels will last much longer shooting cast bullets. Bevel based bullets were designed to drop from the mold easier with the advantage of being inserted into the case easier than flat base. As you mentioned, leading is caused by hot gasses getting past the base of the bullet and depositin melted lead in the barrel. Bevel based bullets don't seal the bore as good as flat based bullets and allow easier leading the barrel. Most commercial cast bullets are too hard and many too small and it's a good idea to measure, with a micrometer, any bullets you buy just to make sure what size they really are. Fit is key to shooting cast lead bullets so you gotta know the dimensions of your gun (slug the barrel to find groove diameter and slug the cylinder throats). Good fitting lead bullets can reach magnum velocities without leading; I've shot slightly over max loads of True Blue under a 358" cast SWC, wheel weight alloy, in my Taurus 357 Mag. with no leading and often shoot 245 gr SWC plain base in my .44 Magnums at over 1200 fps with no leading.).

I cast, but when I want some bullets that I don't have a mold for I buy from Beartooth Bullets Beartooth Bullets > Home. Beartooth makes sever different diameters for each caliber so you can buy bullets that will fit your gun (they supply .357" bullets from .356" to .358" and some rifle .357" bullets to .360").