Thank you for the education. The point of a purpose-built semi-automatic rifle is at least in part to avoid the NFA. If the Army built a semi-auto rifle and called it, lets say, an "M1". Could the Army sell it to civilians? Most likely. Could the Army build a semi-auto rilfe 7.62mm M14NM and sell it to civilians? Most likely. Mind you the conversation is all about purpose built semi-auto M14's, again, mind you these were not converted machine guns. Got it? And, yes , the Army did build a very, very few such rifles. (Mind you these few rifles looked exactly like an M1A, a highly sucessful civilian rifle. These rifles were NEVER made with the selector switch or the switch cut-out. Therefore, no switch was welded shut and none existed on these rifles. Therefore, they were purpose-built semi-auto rifles.)