Thanks for the great links Steven. I took liberty of reposting them on Graybeard Blackpowder site, giving you credit for finding them. I particularly like the working model of what may be a diesel-effect weapon (the site uses the term "oil-powered.)

This is slightly off-topic but if you know anything about early bronze hackbuts, there's a discussion on that site in which we're trying to establish the provenance of one. Bob Smith has contributed, and I've added some information I got from a very knowledgeable PhD from Italy.

http://www.go2gbo.com/forums/index.php/topic,157760.0.html