For non magnum or midrange loads, you want your bullets relatively soft. I like 50% WW / 50% lead alloy. You should to try and match your bullet diameter to the cylinder throat size if possible. When cast bullets lead the cylinder throats, forcing cone and first inch or so of the barrel, it is because the base of the bullet is not sealing the cylinder throat. Vaporized lead from the bullet base is leaking by, etching the sides of the bullet and condensing and being ironed into the metal by the passing bullet. A lot of the older S&W's, especially in 44 and 45 caliber have grossly oversize cylinder throats, so bullets have to upset upon firing to seal. Lower pressure loads need soft bullets to accomplish this, while high pressure loads work OK with harder bullets. It's a matter of matching the bullet alloy to the pressure.