The yoke button was replaced with a shape that let the yoke screw adjust automatically for yoke shake. The cylinder placed a raised ring to help keep expanded gases out of the area the cylinder rides on. A raised shoulder was put on the trigger studs and hammer stud to allow them to ride free of the frame and prevent dirty areas under the side plate binding the trigger or hammer.

I still have my tools I got in the Armorer school but even with them parts will be needed to repair all sorts of problems caused by wear and tear.