"in some environments" being the Vietnam war the US was involved in, in reaction to casualty reports where a large number of men were killed with their rifles

"in some environments" being the Vietnam war the US was involved in, in reaction to casualty reports where a large number of men were killed with their rifles broken down for repair likely due to mid battle stoppages. And the same applies to number of rounds: the entire point of a 5.56mm cartridge was to give soldiers more ammo so they could sustain volume of fire in the field: it was a design goal. If design changes fixed a serious flaw with a weapon, then it was a flawed design.