After MANY years of purchasing a case of shells at the hardware store every September, I was gifted an MEC loader with all the hulls, primers, powder, shot, and wads as the result of a friend's passing. The loader is set up for 12ga, but I would like to scrounge up the conversion parts for other gauges. Do the conversion parts for the several gauges fit the 600 Jr and the 600Jr Mark V? I have reloaded for rifle and pistol calibers for years, but I am quite clueless about shotshells. Thanks