I have found some interesting .303 cases on a hillside in Northern England.
They come from a site that appears to have been burnt and they are badly damaged.
They are marked : DC 40 303 VII and have been fired.
The indent on the primers is not round but rectangular as if the striker/firing pin was more like a hammer on a rimfire?
It is possible that they have come from a crashed aircraft but why would fired cases be on board?
I have a photo that I can email to anyone who is willing and able to post it on here for me.