Privateers hired by the US Congress -- which would include the legendary French pirate Jean Lafitte during the War of 1812 -- all had ships positively bristling with privately-owned cannon.
Furthermore, cannon are still legal to own to this day. Not just the black powder cannon even juveniles can buy from the back pages of comic books and Soldier of Fortune magazine (which of themselves put the lie to Bite-Me's claim), but real, (reasonably) modern military hardware (tightly controlled NFA devices, but legal nonetheless).
Quite a few of the cannon currently in private ownership happen to be attached to a tank, as in an army tank, which also are privately owned, which puts the lie to yet another of Bite-Me's claims (he also lies about not being able to own fighter jets, but there isn't room for that bit here).
Probably my favorite example of a privately-owned cannon being fired from a privately-owned tank purely for entertainment purposes was when the Demolition Ranch's own Matt used the main gun (which is what you call a cannon when it's mounted to a tank) from a war surplus tank to see how much damage the muzzle blast coming sideways out of the main gun tube's muzzle brake will do to a refrigerator.
The tank in question, BTW, also has four (4) fully-automatic machine guns mounted on it, one privately-owned .50 BMG machine gun and three privately-owned .30-06 Springfield machine guns, in addition to the main gun (the bore of which is not stated).
HUMOR ALERT!
You have been warned! Video of the frivolities is here.
I'm not certain but I believe the tank is a, M4A3 "Large Hatch," which originally would have carried a 75mm main gun but this one I think has been "upgraded" to 90mm because muzzle brakes weren't common on the 75mm gun.