Mark II I have worked on a lot of Rem 11 many years ago, they were a great work horse duck hunters gun around here. The A5 Browning has a cut in the back of the receiver as clearance for the firing pin on recoil, the Remington used the fibre cushion riveted in from the inside. There were special tools available for rivet installation and to set the rivet in the cushion. When Remington was Remington, their field service guys stressed you had to have the cushion so when the guy gets an over size shell jammed and they put the butt on the ground and their shoe on the Operating handle and give it a kick start, when the barrel breaks loose and carries the loaded shell back to the no-cushion end of the receiver, wham! Lucky it goes just past your ear.
An old gunsmith of that era that helped me a lot when I started in 1974, had that happen in his basement. Guy with a jammed gun, Andy asked him if it was loaded, no, says the owner, so Andy gives it the kick start, bamm,. right up into the floorboards of the floor up stairs. Later,when Andy is telling me Andy says :look at that, thats the phone wire, Sophie was on the phone just above when it happened. Andy told me he made the guy pay to repair