early carronades sometimes did have trunnions, the more standard later UK form was as you describe, but there were variations. the wood carriage one doesn't use a high elevating screw like the iron carriaged one. later uk ones has the trunnions mounted under the barrel and used the elevating screw on a sliding carriage. the one in the OP's post is tapered from the breech towards the muzzle. it doesn't have the 'usual' step down area. 'usual' implies some did not, ie. is most often there but not mandatory.
i use 'carronade' as a description and function based on it's dictionary definition: a short large-calibre cannon, formerly in naval use.like a 'shashka' (see recent thread on it), the definiton is flexible and can cover a number of related regional and period differences. as an aside 'canon' i believe is the french term for a cannon, but we use english here for a variety of reasons... i lastly show a venerable canon of the salisbury cathedral, which is armed with a number of canons, some of which may be loose.
