I just loaded some 405 grain with Trail Boss. I am Curious to see what the leading does also
Trail Boss is an odd powder, fairly fast burning among other oddities. It has relatively high chamber pressures (fast burn) and also manages to achieve very low velocities! The high pressure expands the bullets (if not terribly hard) and the low velocity provides low recoil, low noise, no sonic crack and I have not noticed any leading. My bullets are the MBC 405 with .459 diameter though. Kind of like a giant .22 Short . They zoom out of my Marlin at about 900 FPS and I swear I can see them in flight with decent light! Good accuracy at 50 yards also.