The autocannon is also a
human heavy weapon in the board-top
miniatures warfare game
Warhammer 40K. Depicted as a very chunky,
long-barrelled,
hip mounted weapon with a large
magazine (usually
belt fed).
Being a heavy weapon, it can only be carried by one member in a squad of Space Marines (the heavy weapon-rich Devestator squad excepted of course) or wheeled around by one fire team of Imperial Guard per squad. The autocannon is a rapid-fire weapon similar to the modern day machine gun. This produces a hail of bullets, evident in the fact that it uses (as of 3rd edition) 3 hit dice for determining hits, before assigning wounds.
Given that the autocannon uses high explosive bolts, it has a very low wound roll, making it quite deadly to massed troops. This means you can rip through any Ork mob or Imperial Guard platoon. Given its armor piercing capabilities, it also has a good chance of wiping out the tougher races - Chaos Space Marines and the like.
Coupled (finally) with the fact it has good range, it makes a versatile weapon on any battlefield. The only potential concerns are the points cost and relative obscurity, which can force people to revert to the heavy bolter as a relatively equal alternative.
Kalon's aside: I know this node is a bit thin on detail with regards to exact numbers like range, hit dice, wound levels, strength, armor piercing values and such, but they have changed the rules 4 times in the length that I have been playing. That and I don't have a
3rd edition rulebook ;-)