Ammo is a stat that dictates the maximum number of bullets that can be stored and fired from a weapon. As the weapon is fired, the number of available bullets decreases from the maximum to zero, at which point no more bullets can be fired. Weapons can be reloaded to regain bullets up to the maximum.

Math

The formula for clip size increase is:  

Sources

Map spawns

  • Gold Urns and breakables can provide a permanent increase: +4% Ammo before 15 minutes, or +6% Ammo after 15 minutes.
  • Power up runes can provide a temporary Gun buff that provides +40% Ammo for 160 seconds.