During the first few minutes of a battle, they seem to fire very aggressively, quickly chewing through two or three hundred rounds.
Once they get down to about 100-200 rounds however, they tend not to fire at all. Further more, once they're down to 100-200 rounds and they get commanded to fire at a particular target (using the F-key/"Fire" button) they seem to fire one burst at the designated target (if the player is lucky) and then quit firing again.
I have noticed this in every game I have played using HMGs and would very much like to see it tweaked. I can't even begin to guess what causes it but it gets very frustrating sitting through tight defensive games with HMGs that, despite having a decent number of rounds left, WON'T FIRE AT THE ENEMY!!

It would be great if this could be explained and fixed.
Cheers,
Andy Brown