Check the stock for cracks around the base, if the wood appears in good shape, replace the screw! or, I have also used a dremel to cut a straight head across a flat head bold & tightened them further with a flat head screwdriver. You may also have to add a washer to the screw/bolt if the wood where the bolt seats is smashed. As already stated, this would be a good place to use some epoxy. I like JB weld! its easy to find & as strong as it gets.