The largest revolving cannon made had a calibre of 53 mm (a little over 2 inches); it fired a shell weighing 1.63 Kg (about 4 lbs.), with 455 m/s (1,500 feet/s) velocity. The gun weighed 1,000 Kg, and required a substantial deck mounting to absorb the recoil.
53 mm Hotchkiss Revolving Cannon on a deck mounting
An Even Bigger Gun
"This gun works equally well, and with nearly the same ease as the lighter guns; of course the rapidity of fire is somewhat less, as the heavy ammunition cannot be handled and fed into the gun with the same facility as the lighter cartridges". [H4]
Where to See One
Alden Park, Mare Island Business Park, near Vallejo, California USA (please send photos for Gallery)
If you know of another, please let me know its location, and if possible send me photos that I can include in the Gallery. See my contact details.
53mm Revolving Cannon on Ship Mounting