Every size--virtually!
"Zamburuks" (Pharsi for "Wasps") were a Class of weapon, not a specific universal design. Commonly associated with armies of Persia, the same weapon type could be found all across India, into Tibet, and most of China, the latter being referred to as "Jingals."
Your description of firing drill is correct, but they could be--and were--fired directly from the kneeling camel's back "broadside" fashion in the service of the Sikh Khalsa. I cannot imagine any practical benefit to trying to fire the weapons from a moving animal.
While most were muzzle-loaders, many could be loaded at the breech with prepared loads in metal forms that could be quickly placed and removed (but please don't think of "rapid repeating fire"--the stein shaped chargers were themselves not very numerous).
Commonly associated with special mountings on camelback, they could also interchangeably be used in a wall gun application, or even an Elephant Howdah piece in Burmese usage.
"Calibers" is probably the wrong way to think of them as the term suggests relationships between barrel length and bore size that did not consciously exist. As most Zambureks were "one-offs," with virtually no two alike, shot weight and size could vary significantly.
Generally speaking, Zambureks could be classified into shot weights of 1-, 2-, and 3-pdrs. Anything heavier was at the point of being impractically large to be man/animal mobile, and justified a wheeled carriage or truck.
While solid shot was the most common load--certainly never anything fused--scrap and homemade "grape" could also be used. Such loads were particularly effective when the piece was in wall gun mode and used to cover approaches, gates, and streets.
In China, termed by Westerners as "Jingals," these same guns were even used for duck hunting! Pea sized, irregularly shaped lead shot was favored in this configuration and was meant to bag multiple birds with one discharge.
In "John Company," it was decided that the limited effectiveness of these weapons relegated them to the equivalent of musketry (though usually in very small numbers) for the chances of inflicting casualties, but granted them artillery status as an influence on enemy and friendly "morale" (a small influence, at that).
The less Zambureks are thought of as "artillery," the closer you will get to reflecting them in a balanced way on your table-top!
Best of Luck,
TVAG
