I was told by Butch (Searcy) that Mercuy recoil reducers in double rifles is not a good idea because, like an air gun, it has both a rearward recoil (due to the shell firing) and a forward recoil due to the gun "running into" the Mercurys "recoil".
This I'm told can (possibly) cause the gun to double. I don't know about you but I'm a little leary of that.