From an image in the AoD rule PDF:

Inferno Ammunition
G-013
26 pts
Requirements: Light, Ballistic
Specifications:
Ignore this gear when the damage value to which it is applied is 0.

(optional) When this unit succeeds at a ranged combat attack that deals damage to a target Mech, the target gains 1 heat in addition to any other heat generated by the attack. When this unit succeeds at the ranged combat attack that deals damage to a target vehicle, this unit deals +1 to that target.

Pretty sweet IMHO...

Might give light mechs a better chance at Heavies...That heat Just might make a difference...

Mid ;)