throw out any steel or plastic cases you run into. Sort them by head stamp; same year, same Manufacturer. Like was said, military cases will be crimped in. Those will be a little tougher to push out primers with. I use a punch and block out of a Lee reloading Kit for this purpose. Then you will need to remove the crimp left behind. Then full length size them. From there you can reload as normal. A new load will have to be developed for each head stamp, they do vary that much. Good luck to you.