I strolled into the local trading post today and they were fussing over a Model 70 Winchester in 243 that they couldn't get apart. The rear action screw slot was completely washed out but the middle and front screw had come out easily. The rifle was filthy and the barrel finish worn but the mechanicals were good along with the bore so I offered to buy it, stuck screw and all. I got it for a ridiculously low price and took it home.
Once home, I took a small diameter Dremel tool abrasive disk to the screw slot and gave it a hard twist with a good screwdriver. Nothing. I made the slot a little deeper and gave it a blood-vessel bursting twist. It came loose, slowly, and finally was removed. Believe it or not, some fool had covered the threads with industrial grade lock-tite. My incredulity at such an act was only tempered by the fact that the guy (gratefully) didn't put it on all three screws!
I will order a new screw tomorrow tho this one will work. Previous "efforts" to remove the screw galled up the triggerguard pretty well but I'll file that out and enamel it. My baby girl snarfed up my old Model 70 243 a couple of years ago. I'm hoping this one is near as accurate.~Muir