To me, you have to break this down to “functional v/s Hollywood” tubes. Plenty of movies have guns that clearly are just made for special effects work, you can see the rammers going in maybe 5 inches or so and very little effort made to accurately portray the correct functions (nobody thumbing the vent, no swabs or worms, etc). Movies like John Wayne’s “Alamo” and the otherwise incredible “Waterloo” are good examples. Some of those guns practically have, ‘Made by Acme’ stamped on the side of them, they’re so poorly done.
Then, you have accurate depictions of what direct and indirect fire looks like. I think “The Patriot” did a halfway decent job of showing the horror of shot into massed formations. “Gettysburg” did an amazing job of showing canister effects at close range. In many movies, you can time the flight of a artillery projectile with a calendar when it’s almost instantaneous in real life.
I know it’s not in the scope of this part of the forum, but I think the most accurate depiction of artillery fire of any kind put to film was the tank attack at the start of the movie, “The Beast”. You watch that and you’ll be seriously wondering if they were shooting live rounds (they weren’t) among all the stunt people.