Well, the tapping worked - only because the tube had lightly rusted in place to the forearm.Tap it gently from the rear with a nylon hammer or something similar, not a steel hammer. Key word here is gently...
I had one that was sticky and I just closed the action firmly a couple times(with the forend screw out) and it loosened it.
I'm shouldn't be surprised as it got soaked (for days) on a caribou hunt years ago and I never thought about taking the fore-end off to, first dry things out and second, oil the tube.
Well my fingers are crossed because I'm going to give a stab at refinshing the fore-end and stock to get rid of the swelling in the wood on the butt of stock caused by the same rains. Lots of checkering to work around, I gotta go find some old toothbrushes......