It's one thing to shoot a gun of relatively recent manufacture that you've bought from someone who says "Yeah, I've been hunting with it / shooting it". It's another to buy a gun of unknown provenance, particularly old military rifles even if they look good, and go shoot it without caution until it's proven to be safe to shoot. If someone has been shooting it all along, there's probably no need for special precautions. An old military rifle from a gun show or a yard sale where there's no reliable history is a different story.