considering that when i served in the military i would sometimes carry a sniper rifle, a assault rifle, a pistol and a disposable AT for some exercises that actually doable
slings, holsters and backpacks make that possible but it sucks i tell you, the weight is horrible which should be represented by the encumbrance rules (and maybe some additional nastiness by the GM, e.g. try going through a normal sized door in cqb combat with such a load)