It should come off. Evidently, there is some stock finish, etc., under the butt plate, that has bonded with the plate itself. Mount the stock in a vise, in a way it wont get scratched. Next, take a rubber mallet, and sharply rap the edge of the butt plate, and see if that will break it loose. If not, try heating the butt plate with a hair dryer, and then giving it a rap.
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