Military use of drum magazines cause several serious problems.
Weight.
Bulky for the capacity
Complexity, both in manufacture, and in loading.
Cost.
Re-supply.
Packing and transportation.
And on & on.
For SAW or heavy MG use, belt-fed disintegrating link is now the standard.
It comes pre-packed & ready to shoot.
You don't have to police up the empty magazines, transport them back, or reload them.
Belts & box mags are not as subject to dirt, mud & damage as drums.
Box mags are the standard world-wide for individual weapons.
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