I'm hoping this might help some folks.
I apologize in advance for the screw heads; they were taken apart literally hundreds of times.
I've since replaced them and found a proper bit for my torque wrench that will not cause damage to the new ones, even over the long-term!
Front view of the prototype that started my business...
... and the rear.
The action is shimmed and the barrel corked:
I also made some cool things like a two-stage Finn M39-style trigger. Instead of pins, it has bearings