M41 Vulcan
From Halopedia, the Halo wiki
Rate of Fire : 450-550 per minute
Fire Mode : Automatic Ammunition : 12.7x99mm armor penetrating rounds Damage per Hit: High Range : Medium to long Accuracy : Medium to High Magazine Size : none drum-fed weapon Maximum Ammo : unlimited Scope : none 3rd person view
Summary
The Warthog's M41 LAAG AA gun is a three-barreled, electric-powered, linkless, drum-fed weapon. It fires 450 to 550 12.7x99mm armor penetrating rounds per minute. Turret traverse rate is 100 degrees per second and weapon elevation rate is 60 degrees per second. Recoil from sustained fire is prodigious and negatively impacts accuracy at long range.
It is the standard equipment on the M12 LRV Warthog.