There were semi-auto M3A1 "Grease Guns" made by Valkerie Arms as well as the M60 H&R Reising. I've had a couple of M50's and have to agree with Jim that they don't compare to the M1/M1A1TSMG. They run just as fast and are hard to hold on to in F/A fire. The weight and balance of the M1A1 is perfect once you know how to use it.