I wanted to get opinions on a Remington 31 pump shotgun I use on a regular basis. The 31 is a precursor to the 870 and several other shotguns in use today. When I fire heavy 2 3/4 loads in it, the action will open on its own anywhere from an inch to almost fully open. I ruled out it being related to recoil and my hand on the slide by firing it without a hand on the slide. Even with that test, the bolt does not go far enough back to eject the shell, but it goes back several inches. A Web search on this phenomena yielded two camps; one says it's working fine and as designed, and some say it isn't. What say you?