Try as I might, I can't seem to loosen the buttstock screw.  The screw is starting to strip.  Any ideas on ways to loosen it up?  TIA

Try Liquid Wrench, available at any auto supply store or Home Depot, or--even better--Kroil, though it's a little harder to find. It's not common for one to become so frozen but it does happen.

Also, if you're using a standard screwdriver instead of a gunsmith screwdriver--parallel ground sides--try to find one or grind a regular screwdriver to fit the screw exactly and grind the sides parallel so it won't try to torque out of the slot.

Thanks for the tips!  I eventually got it, but it was virtually frozen solid.