The cannulure in the case was a crimp to hold the bullet in a tubular magazine, I'm thinking. Lots of original paper patched bullets for magazine rifles had that because they couldn't crimp the case mouth because of the paper.
I've got some 11 mm brass, it isn't cannulured, but the case head is funny-shaped. At any rate, they likely didn't use real bullets and real cases in the movie.
I think there must be a prop company in Hollywood that has that Remington Keene rifle; I've seen it before in the "Sons of Katie Elder." The bad guy was firing off a few rounds at a target with it.
