I used to shoot the RCBS 255 grain SWC. With my alloy, lubed and sized they came out at 270 grains. I used 25 grains of Win 296 and Winchester std large pistol primers. That's a real wide, flat nosed SWC, almost as wide as the LBT designs. That's way more "thump" than you need for deer, but I never was able to get good accuracy out of my particular Blackhawk with lighter loads.
