I have read about the total nightmare that was the XM16, the feud between MacNamara and Army Ordnance, the shenanigans, and the stupid orders that soldiers got, that did get many Americans killed. Criminal behavior, to say the least. There was even a congressional hearing in 1968, and heads should have rolled... but, of course, didn't.... It's pretty maddening, really, and I have no personal axe to grind in the situation.
They did, however, finally get the gun worked out. The M16 of 1967 is not quite the same thing as the AR today.
