The auto shotgun is an eight-barreled, semi automatic, mechanically indexing firearm that fires shotgun shells. When the fire key is pressed, one shell is shot, then the gun indexes to the next barrel. Since the gun automatically indexes to the next loaded barrel, rather than manually re-chambered with a pump, it has a slightly faster rate of fire over the 12 Gauge Pump-Action Shotgun, although the two are comparable.
Unlike the Serious Sam 1 shotguns, the auto shotgun has a very tight spread, making it usable at even long distance.
- The auto shotgun works best against weak enemies, such as Orcs and Beheaded Kamikazes. Its fire rate allows the player to tackle up even large groups of weak enemies with ease. It can be a useful alternate to the Colt Anaconda if the player needs to take out a group of small enemies, especially if they don't have enough time to use the anaconda.
- Because of its tight spread, the auto shotgun also works well against enemies at long range. However, it shouldn't be used against medium or strong enemies because of how little damage it does when the target starts coming close.
- If the player switches their weapon directly after firing, and then switches immediately back to the shotgun, the player can fire without having to wait for the next barrel to line up. This allows the player to fire at a drastically increased firing rate so long as they can maintain the pattern.