Not to mention simplicity and versatility of production. Instead of having factories split productions between fighters and tanks, they all produce a MAS fit for both.

And yes, artillery is direct fire in space. Caliber size came from reading the default MAS, heavy cannon idea came from the reknown AC-130. Autoloader came from tanks though :3j

Also, smaller than 20mm is a machine gun. 20-40mm is an auto cannon. Anything bigger and that is a full size cannon.

Around the time when you need to start using cm or inches, that's when you're dealing with naval artillery.

EDIR: Who's the flying fugue that Gerard grabbed?