I'm just sitting here trying to calculate how much force a MAC would have behind it.

The barrels of the cannons themselves are 2 feet wide and 9 feet long. 
The rounds it fires are 250lb slugs of tungsten.

MACs are pretty much just Gauss guns, but bigger. They're a magnetic coilgun and they would speed up that slug of tungsten to around 10,000mp/s as they're three stage cannons. So 250lbs sped up to 10,000mp/s would produce. . .

Ech, I don't know the formula for force.