You might try heating the cocking piece slightly with a propane torch and hope it will expand enough to go free, or, you can clamp the cocking piece in a vise and apply force against the bolt shroud via a hardwood block and a hammer to separate the two. If you don't have a disassembly tool that holds the shroud and firing pin, then be prepared to chase parts.
Lock, Stock and Barrel gunworks
SLC, Ut
USMC 69-73
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