These sometimes have case splits, maybe the first case, came apart blew pressure back in the action and tore out the extractor, I am not sure about the second shot that you call a misfire, but if the case in the barrel is from the first shot he can be glad, the second shot did not go into an obstructed barrel. Not sure really what happened, by your description. Another possibility is the bullet when chambered, was pushed back into the case, when fired this raises pressure, and allows some gasses to escape around the bullet, not sending the bullet all the way down the barrel. Check your unfired shells for neck splits, and see if you can easily push the bullet farther down in the case, the case does not have to be split to have this problem. If you can push your bullet down in the case, then that is a good indication of your problem.