I have this scene stuck in my head and for the life of me I can’t remember where it’s from.
Basically I think it was a war movie made in the 70’s. A group of guys on a train going off to war decide to take pot shots at cows as their train goes across the countryside. They hit a couple until the protagonist chides them for pointlessly killing cows when they’re going to be killing real humans soon.
I also remember a really fake looking shot of a cow getting shot in the leg and collapsing but that may have been from an entirely different film.
There’s a scene exactly like you describe from the 2010 HBO miniseries *The Pacific *- could that be it? It’s in one of the earlier episodes, and takes place in Australia.
I know it’s not what you’re looking for, but I immediately thought of scene in Unforgiven where English Bob challenges a couple of other passengers to shoot birds while riding a train.