In 1963, the Army initiated a program to weld selected M14 rifles to a permanent semi-auto configuration and sell them through the DCM to civilian high power competitors. They even produced an Army Regulation* as to how this was to be done once the program was approved.
There was no problem with (then) ATTD. The United States was the legal manufacturer and owner of the rifle, and the manufacturer would simply have been issuing a new model, to be designated the M14M. The second "M" would be marked on the receiver once the conversion had been done. Some rifles were converted, but NONE were ever sold.
Well, on November 22, 1963, an event occurred that had many consequences. One was that the Secretary of the Army cancelled the M14M program, ordered that NO M14Ms were to be sold, and that while the sale of M1903A4 rifles could continue, the scopes were to be taken off and broken up with the lenses used for "educational purposes." The whole thing was CYA politics by the Army and the Johnson administration. (For those who aren't old enough to remember, there was legislation introduced to ban all hunting, ban all guns, ban all rifles, ban all scope sights, round up NRA members and hunters to be put in "re-education" camps, etc. It was sheer insanity and there was no way the Army was going to sell "machineguns" and scope sighted rifles in that political atmosphere.)
M14Ms and M14NMs were in fact later loaned to state associations for use by their teams, but none were ever sold; they remained the property of the U.S., the same as those M14s loaned to police departments.
Just as a tickler, there is NO legal reason the M14M program could not be revived today. It is not likely it will be. The 1986 ban on machinegun registration would not apply, as the M14M would not be a machinegun.
*That AR crops up every once in a while, and some folks say it requires the Army to release M14s for sale; it does no such thing and an AR does NOT over-ride Army policy or federal law.