I shoot a couple of 30-shot bullseye scores approximately twice a month & keep track of my scores. I shoot one round with a S&W Mod 41 & another with a Colt national Match 1911. At first my shots are inside the 9-10 rings but as I begin to tire with the S&W Mod 41 my shots drift to the right of the bullseye and with the 1911 my shots drift to the left. Is this a grip issue? .