I've been curious about the "Mc. House Cannon" shown on pp. 6 of BoomJ's post, ever since I found it on the web and posted it on this board a couple of years ago. I'm a bit surprised there's no comment in the article that the cannon itself is mounted upside-down, so that the inverted marks on the trunnions are now right-side up. Clearly no muzzle-loading cannon I've ever seen has trunnions above the bore centerline, so it must be mounted upside-down. Might there be some marks on top of the gun (now on underside) that no one's seen?
For DD, I have a copy of a very thick document, "Rep. No. 141, National Foundry, March 3, 1835, Congress of the United States." Most of it consists of a report by CAPT. Thomas ap. Catesby Jones, of an inspection he conducted of some 2400 naval guns at six different Navy yards. There are probably a couple of dozen 18 pdr. carronades in the report, which gives several measurements for them, and descriptions of features (raised vent for lock or not, hole for screw or not, breech ring or not, etc.) There are no drawings. However if the measurements interest you I could find a way to summarize them I think. The data tables themselves are strung out for a few pages and thus would not photograph in any comprehensible way.