Another thing that seems to be missing is a "tail."

A swivel gun would have to have an arm or " tail," so the gun could be
swiveled or aimed.

Some swivel guns would also have a yoke, or cradle to hold them.  In such
an arrangement, the yoke would have the mounting stem or pivot piece and
not the gun itself.

How much does this gun weigh?  To be picked up and manhandled into position
on a ship's railing in any kind of sea, a swivel gun can't be too heavy.

Carl Barna
Lakewood, CO