Here's examples of the ammo packaging. The 7.62 started in 20 rd honeycomb packaging and evolved to clips at the end. Too late, right? You see one box marked just ball and the other plainly clips.
The 5.56 started in boxes and had clips, one mag charger came in each steel box. 1120 per steel box I think? The other guys get to load singles. Later bandoleers had a charger per bandoleer. The 5.56 pictured uses a heavier bullet than I did, a result of Afghanistan I bet.
You'd have to ask guys here like DaveHH and others about RVN and US issue, there's lots of them around. They could tell you about the US issue of 7.62 and 5.56. The UKtroops used to leave dozens of 50 rd plastic boxes behind from 7.62 also. I still have some I think. Gil Boyd and Peter L can fill you in there.