Overwatch uses "ammo" in that sure you're attacking more often but at the loss of ammunition or shots - if you will, now couple that with limited "clips" on the character's person (explain to me how and where you have more than 3 clips on your person is my common GM question for any type of gear, if its explained logically then by all means the PC has it)...
So as far as I can tell the foil of the mechanic being finite ammo
Stay GAMING
Morbid