[Ron Wood]

I have never tried this suggestion, but I have heard that after applying penetrating oil and tapping the screws the last measure that can be taken is to heat a cheap screwdriver that is slightly narrower than the screw slot to red hot and then heating the screw to give it that last bit of encouragement to break free. This applies a more directed heat source than a hair dryer or heat gun. You want to keep the screw driver narrower than the screw head so that you don't accidentally burn the wood grips. I have never had any screws seized to that extent so I don't know how well it works. Good luck.