Vietnam ammo loads were quite often dictated by unit, and varied greatly. DePuy when he had the 1st ID was very specific in his instructions. SOG tended to carry more ammo than most, which was understandable given their mission and typical AO. It also depended on how frequently a unit could expect resupply. Outfits like the 1 CD, who had many, many helicopters, could resupply once a day (if not more). Others (like the aforementioned Americal or 4th ID) carried more because they could resupply less.