The 15 cwt gun was intended for broadside use on sloop-class ships, and the 13 cwt gun was known as a pinnace gun and was intended for boat use.
The 15 cwt gun was intended for broadside use on sloop-class ships, it has a raised coil in front of the vent slot. The more lightly constructed 13 cwt gun was known as a pinnace gun and was intended for boat use.