Please don't take this the wrong way, but there is probably a 98% chance that this all could have been avoided by simply using a better penetrating oil than Kroil and giving it several weeks to soak into the threads, reapplying as necessary. The sprint to the finish line has damaged a LOT of guns.
The end result would be that you would have original screws and threads in your gun, and you would save the time and expense of searching out and buying metric taps and making or buying new screws.
You might get mad at me for pointing this out, but rest assured I made the same mistake of getting in a hurry to finish a project when I first started working on guns. In the grand scheme of things, it usually takes less total time, and a lot less money, to simply wait and let a good penetrating oil work.
Please don't run an M4 tap of different thread pitch into your action screw holes. You will end up with a gun that has been repaired beyond repair.
