Yes well I need my 18th-century field cannon to have serious kickback, and flintlock ignition when it probably would have been slow match. And so I’m sabotaging my gun so the trunnions have broken free of the carriage, having learned that those barrel projections are called trunnions, and I’m taking artistic license with the flintlock, and history buffs will just have to eat it. I’m getting lots of other stuff wrong anyway.

Serendipitously, the required sabotage of my fictional gun fits perfectly with another aspect of the scene, so bully for me and my cannon.