I've always found it useful to model my fictional weapons after real-world ones - in this case, the 40 mm Bofors L/70 cannon. Keeps things plausible and easy to figure out.
[@vietmyke]I was wondering, are MAs without the tesla drive or booster upgrades restricted solely to walking speeds, or can MAs 'skate' around the ground with wheels or some sort of low-power boosters? As in Front Mission, VOTOMS, etc.