Frank, that is one of my 1957 favorites featuring Sophia Loren and the big cannon. The title was "The Pride and the Passion". Cary Grant was also in it. The big cannon looked like a prop to me the way it twitched and jumped over some little rough spots on the mountain as it gained speed going downhill.
My personal favorite of 1966 has to be the best spaghetti western ever filmed, The Good, The Bad and The Ugly directed by Sergio Leone and featuring Clint Eastwood as Blondie, Lee Van Cleef as Angel Eyes and Eli Wallach as Tuco, the Good, the Bad and the Ugly. Besides having all those great cannon firing during the Civil War battle scene on the hill overlooking the bridge and the river, you also had Blondie, the gunner, with his lit cigar and the field piece loaded and fused. Tuco was the moving target, of course. Remember that line uttered by Tuco as black powder smoke swirled above his bubble bath as the bad guy staggers backward, mortally wounded? Tuco says, "If you're going to shoot, shoot; don't talk!" Great movie!
TK