Had to salvage a rusted 28-2

[AJ]

trick with rusted screws; put a little pool of pentitrating oil around the screw head. leave it for a couple hours and tap on the screw head with a punch.

Was taught by my Metalsmith's to tap the end of a screwdriver while attempting to turn it. Worked well for us on the aircraft and the few times that I have had to use the technique on a gun.