Thanks for bearing with me; I am understanding a bit more now.

One thing I do remember from that period was Stoner trying to interest the US military in the new rifle, which he said was sort of a product-improved M-16. One of the big selling-points was the interchangeability of the magazines. It was mentioned prominently in several articles in the gun mags of the time... but evidently they are not strictly interchangeable.

I hope the above tidbit excuses my treading upon thin ice.