Not sure, I didn't investigate the shell but I looked like everything was fine with the gun. The one thing it could be is that I left one 3 inch shell on the chair in the blind and we had a lot of rain and about 5 inches of snow and the shell was wet or something like that. The shell didn't seem wet when I first put it in the gun. I jus had one shell so I was using the same shell. It only takes one shot so I never brought any more shells with me. I did have a few more in the truck. LOL