Possibly the one support weapon with the largest capacity available, is the MK48 your dream support weapon?
The VFC MK48 MOD1 Deluxe AEG is probably the ultimate airsoft machine gun and it is probably the only machine gun you will need. This machine gun is of a lightweight design, even though it is of full metal the gun only weights a shy of 4 KGs.
However the main star of this gun is its capacity, a whopping of 8800 rounds with the drum attached! They did this by having a BB reservoir in the gun itself, which by its own could hold 800 rounds, the drum holds 8000 rounds. This super high capacity makes this the perfect gun for any airsoft machine gunner out there, not only that it is light, it can also shoot much longer than its competition.