The cost on this upgrade is 2, not 1, and should be updated accordingly.
Additionally, Gauntlet Gun's wild resources can only pay for War Machine events, of which there are 8:
Gauntlet Gun generates ammo counters, which are absolutely key to War Machine's success. Aside from the events above, ammo counters can be used by two of War Machine's upgrades:
- Missile Launcher: 2 damage per turn at the cost of one counter. Can clear Stun, is Ranged, which is cool for dealing with Retaliate enemies.
- Shoulder Cannon: 1 free damage per turn, plus one per counter spent. Dumping ammo through this is a very good way to end a game, or put minions in range of kills by other events or attacks.
The upside is that Gauntlet Gun can be used when paying for other cards and abilities, BUT the resource generated does nothing. This is just a way to farm up ammo counters if you're otherwise lacking War Machine events but have Missile Launcher or Shoulder Cannon to burn up your ammo. This should be clarified by FFG that the interaction is intended, though the intent or the card design seems clear to me.