[TARNATION !!!]

Problem resolved. Barrels unhook with hammers cocked or dry-fired. Guts of action were in good condition with minimal foreign material. So what was the issue you ask. It was the smallest screw that I think is inside a Parker. It is on the side of the trigger plate and allows the un-hooking slide to travel within prescribed limits. It is discussed in Brian's article. When I opened everything, the un-hooking slide was indeed stuck in its most rearward travel position. I found a jeweler's screwdriver that was the right size for the small screw. I don't think I did much more than start to back out that screw and the un-hooking slide snapped forward. I disassembled and re-lubed everything (lubriplate). When running that small screw back into place, I kept pushing the un-hooking slide to ensure free travel. I then wanted to see what it would take to stop the un-hooking slide and it was not very much more rotation than a properly aligned screw head. Fine tolerances. Must have been over torqued along the way in the history of this gun. Will be trying it out tomorrow for wild pheasants. Cheers, Jack