Seems my eldest Shadow (about 3 years old - not all that much use on it) is "mushrooming" a bit, at the top of the compression tube right where the tube and the breach block meet (above the transfer port). The top of the breach block has a slight matching indentation where the receiver hits it.
Obviously, those parts have been hammering each other. It ain't too bad, there's no 'barrel lift' from it. I doubt it's from closing the breach (I use my hand, not a hammer for that!), I'm guessing it's just from the piston slamming home.
Has this happened to anyone else?