it because you book has loads only for the single action army and it replicas(around 15,000 cup) the blackhawk,vaquero,bisley,freedomarms,or tc contender can run at 30,000 cup at that level you can push a 300 grain xtp at 1290 fps to put it in persepective a 44 can push a 300 grain xtp at 1310 fps the colt passes the 44 once you get lead bullet weights of 330,340,360----------------- i personaly use a load of 22.0 grains of h110 and a 300 grain xtp (the max is 22.2 according to hodgodon) it was the most accurate and according to the chrono it comes out my barrel 1195 fps 5.5" barrel