What we currently call the “M4″ has been, in various forms, our standard Infantry rifle since the 1960s.
As with any new piece of critical equipment that is haphazardly rushed into service in the middle of a war (Vietnam), testing was inadequate (much of it glossed-over), and there were thus a number of “start-up problems” when this new rifle hit the field, some of which proved fatal to more than one young soldier!
The episode represents an unsavory chapter in our military history, and many in my generation have not forgotten, and never will!
Over the next sixty years, the rifle and caliber (5.56×45) stuck around. In fact, we still have it. To their credit, the Pentagon has since made many improvements, addressing specific issues. And, our industrial sector, producing M4s for the consuming public, also made changes. Some good; some silly!