[El Gato]

Once a firearm reaches a certain calibre, it no longer falls into the arms definition, but then becomes ordnance. A cannon falls into this latter definition. The same is true for items like RPGs, bombs, nuclear weapons, etc.

That must be why we negotiate arms limitation treates with foreign nations. Wouldn't want them to have too many small arms. </sarcasm

Arms includd cannon in the days when the second amendment was ratified. If you, or your group, could afford them, you could own them. And the Constitution means now what it meant then.

[Robert357]

Once a firearm reaches a certain calibre, it no longer falls into the arms definition, but then becomes ordnance. A cannon falls into this latter definition. The same is true for items like RPGs, bombs, nuclear weapons, etc.

You actually might want to check out post 177 and the link to the definition of a destructive device. I suspect that the legal term you are searching for is not ordinance, but destructive device.