[Brian61]

Small crew served weapons, once deployed, only need two people to fire them (actually can get by with one though rof would drop off). The extra men are mostly ammo bearers, once they drop their ammo loads nearby the weapon, their job becomes observer/close in fire support.

It does bring up a question of why the crews for MGs in particular are so small, an early war german HMG section with two HMGs included 12 men + wagon drivers for example.