I still want to know why McNamara closed it down.
Robert McNamara came from Ford Motor Company, where he was one of the original "Whiz Kids". They were a group of former U.S. Air Force officers who were instrumental in putting reliance on statistical data into the new Air Forces systems and overall structure.
When Henry Ford, II, took over Ford, they were nearly bankrupt, and he hired these Air Force Officers to bring systemic thinking and order to Ford. A number of them remained at Ford, and some left to create their own companies. Among them was "Tex" Thornton, who founded what was to become Litton Industries. J. Edward Lundy remained at Ford, and became the most powerful CFO, and some say most powerful executive ever, at Ford.
McNamara rose to the position of president in 1961, but left shortly thereafter, to serve as John F. Kennedy's Secretary of Defense.
McNamara did not like the way that small arms were designed and developed using the armory system. He made it his task to shut it down, and find outside suppliers to get in on the firearms development and procurement processes.
So, after Curtis LeMay had contacted Armalite and contracted for a number of AR15's, McNamara decided to expand the procurement and the saga of the AR15/M16 began.