Who did you serve with?
That looks like a brand new M16A1!
My dad was with Kilo 3/9 near the DMZ from June 1967- July 1968 and he told me a while back that around the December 1967- January 1968 time frame they had to all line up next to a truck full of brand new M16A1s. As they made it through the line, an armouror looked down the barrels (or chambers) of the XM16E1s they all had with an expensive looking piece of equipment and about 1/2 the guys got new rifles. My dad wanted an new one so after he was told his rifle was OK on the first passing, he rubbed dirt all over it and went through the line again. Declined. Before his third pass through the line, he took a coat hanger and tried to scratch the chamber all up so he could get a new rifle. Declined again.
After messing the rifle up with the coat hanger, he was worried he ruined it, but it turned out OK.
He remembers the new M16s had the birdcage FH and his had the three prong.
Did you ever go around on the trucks looking down Marines' rifles like the story above?
Thanks for your service and welcome home!