The M-14 is a difficult weapon to produce. McNamara went to M-16 in large part due to numerous delays in M-14 production by Springfield Armory and other producers. M-16 family was easier to produce in quantity.
Look at current semi-auto M14 production - costs as much to by a forged M-14 receiver as a entire AR-15. The supply of M-14 parts is running out and the cast copies have a poor rep.
Bummer, that.