I trained with the M16A1 in boot camp and got the M16A2 when I got to ITS-San Onofre...they were new to the Corps at that time.
The 16 is lightweight, holds lots of ammo, and in the A2 version..a very accurate rifle even out to 500 meters. It has a ton of stuff you can hang on it, if one has the desire to do that.
Sir, we must have been in at the same time. I had the 'A1 in boot camp and the 'A2 in ITS at Camp Geiger (Lejeune). The '16s we had then were remarkably accurate and very reliable. The only failures I personally saw with live ammo (blanks are a whole 'nuther thing) were magazine related. The guns always ran fine: rain, snow, mud, sand, bitter cold to scorching hot, whatever.
I never had to shoot anyone with the '16, but I do think the 5.56 cartridge is too small for infantry use. Infantry have to shoot things other than just people, and a heavier round is better for that.
JMHO, FWIW.
Hope this helps, and Semper Fi.
Ron H.