the reason why ya need so many mags isn't as much a tactical concern but more of a logistics one--
if the big "O" steals this one, passes a ban the USA itself is gonna change-- you might not ever have another chance for re-supply of ammo or mags.
the ones you got are going to have to do for a couple decades if we all live that long.
if things get really bad you might have to split the collections up, then each firearm will have its own small supply of mags and ammo--
you might not need more than six mags at any one time --but it sure would be nice to have a few spares scattered around the AO--
PS the m4 is very light-- till you stick flashlights, lasers, optics, rails, bi-pods-tripods, battery packs --LOL--
that optional beer cooler takes a lot of D-cells! LOL!