I have used 21 grains of Trail boss with a 405 gas checked bullet which is quite accurate but I have not crono it. I am not fond of that blue wax lube Blackhawk cast bullets have on them. I have found that the conventionally lubed bullet to be more accurate. With a gas check I have used 51 grains of 2207 with a 405 grn bullet without a problem. Reasonably good accuracy.