An Autocannon is a type of rapid-firing, auto-loading direct-fire ballistic weapon, firing HEAP (High-Explosive Armor-Piercing) or kinetic rounds at targets in bursts. It is, basically, a giant "machine gun" that fires predominantly cased explosive shells though models firing saboted high velocity kinetic energy penetrators, though caseless ordnance do exist. Among the earliest tank/BattleMech scale weaponry produced, autocannons produce far less heat than energy weapons, but are considerably bulkier and are dependent upon limited stores of ammunition.
Autocannons range in caliber from 30mm up to 203mm and are loosely grouped according to their damage versus armor. The exact same caliber of shell fired in a 100 shot burst to do 20 damage will have a shorter effective range than when fired in a 10 shot burst to do 2 damage due to recoil and other factors. Autocannon are grouped into the following loose damage classes:
Beyond the "standard" models, variants include the shotgun-like LBX, quick-firing Ultra and the gatling-type Rotary. Light-weight variants and capital ship scale models also exist. The experimental Hypervelocity Autocannon has also entered limited production.
Caliber is fluff for the size of the barrel that the shell or shells are fired from and no standard caliber has been set for any of the classes of Autocannon. Autocannon in a class vary by manufacturer and model. With the fluffed number of shells and caliber being specified, no Autocannon has been specified to be one shell fired for each "round" or burst of fire. A possible exception is the 203 mm Ultra Autocannon/20 on the Cauldron Born A BattleMech.
- TechManual, p. 207, "Autocannon"
- Tactical Operations, p. 285, "Autocannons"
- Experimental Technical Readout: Mercs, p. 8, "Warrior HX-9"