It is hard to imagine any 18th century ship without cannons. It was certainly the ship’s main weapon of destruction. We cannot talk about exacts characteristic of pirate cannons. That is because there were numerous types of cannons by every means. As term - cannon are referred to any gun mounted on the ship. They were hard to operate, and usually required up to six men, leaded by gunner who was very important in a chain of command on a ship.
There were many types of shot used for cannons and pirates preferred ammunition that would not destroy ship they wanted to plunder, just people in it. Almost every cannon had additional tools such as worm, rammer and sponge. They evolved through time. Earliest versions were expensive, built from bronze and latest and much cheaper cannons were form iron. They loosed weight, reloaded faster, and became more accurate.
Swivel gun is one of smallest type of cannon. They were much lighter than normal cannons, so they could be quickly mounted or demounted on any pirate ship. Their main purpose was to kill people on deck before boarding, and not to destroy ships. As this weapon was mounted on swivel, they have great mobility and wide range. That made swivel gun a perfect defensive weapon in repelling boarding. They fired all types of ammunition, but especially grape shot. Accuracy was low so enemy had to be close before firing swivel gun.
Carronade were developed by Scottish Carron Company in 1778. The Royal Navy used them a lot more then pirates. They were short-ranged cannons, which could deliver the large amount of damage. Contrary to swivel gun, these cannons were mostly used for destroying ships with heavy cannonballs.