Hello again. I have managed to re-start my project and making some headway. I believe I said in some earlier part of this that I needed to modify the receiver and add more mass in the standing breech area. The original Mod. 21 has 150 thousands of thickness there and that is not enough in my view to either allow for a bushing for the firing pin and add strength for any plastic deformation. I think that is the main problem that the gunsmith in Colorado had with his set of 7x57R barrels unhinging. Of course he used an original receiver. As we started milling we left 550 thousands for the standing breech only to find that even a modified hammer would hit the butt stock. So we took out an additional 100 thousands. This still leaves 450 thousands. Then we needed to redesign the hammer since the original hammer was a single integral hammer and firing pin. I have posted below the redesigned hammer. I believe it will work. Anyway some pictures:

This is the starting for the back of the receiver.

The raw receiver next to an original Winchester 21.

Setup in the CNC mill making the first hole for the locking lug.

Milling out the back.

I will post more as I make progress.
Bill