The bullets are chubby so size a case , slit it with a dremmel cut off wheel and insert a bullet into the brass and push it into your chamber. Push it hard so the rim is up against the barrel hood and then take a pencil and push it out gently from the muzzel end. Measure the OAL and you have your max OAL before it hits the rifling. In my barrel ( short chamber ) it measures 1.070, so I set my OAL to 1.050.