I am interested in trying to help you get your shotgun running again because I had the same problem I couldn't change the cockers without beating up the shotgun. There is more than one way to skin a cat, is one of my favorite sayings.
Have the cockers been altered?
Does either barrel fire or does the shotgun not fire at all?
With the shotgun in the fired condition, hammers not cocked, pull the forearm and barrels off .
Is either firing pin sticking out and if so, how far? should be about .050" or if you don't have a way to measure it, lay a dime on the recoil
shield , firing pin should be sticking out about that far.
Hope I can help you, if you're not interested, that's fine too.
