BATF " once a machine gun, always a machine gun " 1969 small arms of the world lists M14m. The m stands for modified. The selector shaft had been welded so as to prevent the use of the full auto parts. These M14 ms were sold at Camp Perry in the 60's to CMP members and state rifle clubs. In the early 70's is when BATF came out with the rule once a machine gun always a machine gun and went out to collect the ones sold at Camp Perry. A few people Registered them during the 68 amnesty.