I took a buddy of mine to the range with a barely used mint PTR91 I found for him on the AR15com forum. The only ammo we took was Israeli IMI 7.62, but the rifle would not fire any of it. It didn't appear that the firing pin was even striking the primer. I took it apart and the firing pin doesn't appear damaged, still round on the tip. We tried several times but no luck, the former owner never had a problem with it. Any ideas?