I’ve dabbled a bit in the Infantry/Special Ops business, but have never actually been “shot at by anyone who really meant it” ...
I remember loading up the backpack before heading out ... throw in some ammunition, and a canteen, and some more ammunition, and a few parachute flares, and some more ammunition, and some smoke grenades and a sleeping bag, and a little more ammunition, and some C-rations and a couple spare pairs of socks, and a little more ammunition, and pretty soon the darned pack weighed half as much as I did.
My own preferred cartridge, .30-’06, with 168 grain bullets seems to weigh about 30 lbs per 500 rounds.