Attached Link: http://www.wordiq.com/definition/M16A1

M-16 showing the later model 30 round clip. I doubt you will find any 'Nam photos with soldiers with these clips. Maybe some Rangers or Green Beret's had them, but not regular troops.

I was in the Army in 1970-71 and trained with the original M-16, which had the straight clip. Got an Expert rifleman badge- due probably to the fact that I had also had NRA training while a Boy Scout a decade earlier. Learned breath control and how to mentally think where the round should go... but never fired a shot in anger either as the Vietnam War was ending as I was in advanced training.

Apparently troops in Iraq STILL tape their clips together, even though they aren't supposed to officially.