Rear sight
Take a brass punch, and hammer, and tap the sight to get it to move! Be careful, because there is a Firing pin block plunger that protrudes through an opening under the sight, and it is under spring pressure, so don't lose it You may have to tap it pretty hard, if it is really stuck, and also try tapping from right to left. Also you may try some WD-40 on it prior to tapping.
