AutoCannon 5

The AutoCannon is a direct-fire ballistic weapon, firing HEAP (High-Explosive Armor-Piercing) rounds at targets either singly or in bursts.

An AutoCannon/5 can use special munitions that modify the properties of the shot.

History
Designed for the Terran Alliance, the prototype version of this cannon was among first autocannons ever made. It first appeared in 2240 and was designed to improve the Alliance's military arsenal cope with newer armor being introduced during the time. Examples of the Prototype AC/5 being used was on the Saturn-Class Patrol Ship in 2243.

Autocannon ratings
Different manufacturers and models of autocannons have different calibers (25mm-203mm) and rates of fire. Due to this, autocannons are grouped into generic "classes" of autocannons with common damage ratings, with Autocannon/5s usually having a long range with a small to moderate damage level.

An example of the rating system: the Crusher Super Heavy Cannon is a 150mm weapon firing ten shells per "shot", while the Chemjet Gun is a 185mm weapon firing much slower, but causing higher damage. Despite their differences, both are classified as Autocannon/20s due to their damage output.

Armstrong J11
Designed by Armstrong Industries of the Free Worlds League, The 80mm Armstrong J11 autocannon is a reliable weapon with only a small chance of the weapon jamming when the barrel or reciever assembly are extremely hot.

General Motors Whirlwind
Famously mounted on the General Motors Marauder BattleMech, this autocannon fires 120mm shells in three round bursts.

Imperator-A
Carried on the Rifleman, Imperator-A autocannons fired in five-round bursts.