@ $10 round & 500rds/min, that's an expensive toy to shoot...  (airborne version shoots 600rds/min)
I went on a gun-run in Phoenix once where the armory wanted to clean out some old inventory, they literally filled the floor of my 53 with cases of 100-rd belts.  3-5round bursts???  No way, I was doing 50-round bursts and turned my gun cherry red, more than once.  I also cooked off a couple of rounds when the gun was glowing like that.
; )