Hi
If it is once fired, the primers should be crimped in, and hard to remove from the brass. They sell special punches to deprime them, I changed out the pin in the sizing die to a number drill, so I could just size and deprime. You need to remove that crimped material to get a primer in, they sell a primer pocket swagger to do that. Also most military will have a year date on the back along with the head stamp. They are heavier, the brass is thicker and Sierra suggests, 1 grain less starting load. If they have been reloaded some one will have had to "fix" the crimped part of the case.
Hope this helps
jim