Actuallyits the rings on the magazine tube. With the bolt foreward, they are pushed against the ring for the barrel not allowing them to shake around, with the bolt back there is room for it to shake around.

They are not located between the piston and the receiver, otherwise it would always be making noise and you would have to take the bolt out to clean the rings, which is a pain to novice gun owners. A lot of residue build up on them rings. Clean them often, whatever you do don't use oil on them otherwise the residue will built up right away and your gun won't be cycling the shells, I just use a little solvent.

To be more specific, all remington auto shotguns do it. Not all autos.

Nothing to worry about. When your hunting the gun should be loaded anyway. Can't kill anything if the gun isn't loaded.

Just to see what I am talking about, with the action open take the forearm off and while holding the barrel or putting the magazine cap back on, tilt the gun upward and downward and you will see them slide on the magazine tube.

BEFORE YOU TAKE THEM OFF TO CLEAN, KNOW HOW THEY FIT ON THE GUN/the order they go on the magazine tube.