More detailing of the changes made by this prototype...
The top view of the receiver ring (conversion on the right - like it is no obvious huh?
) Also notice the difference in the thickness of the barrel flange on the 9mm barrel and the barrel stub in the conversion receiver.
Changes to to rear and forward toggle linkage. Note the movement of the toggle coupling link and the difference in physical size of the coupling links. The conversion coupling link is much thicker. I am not sure if this link is original or fabricated... but original would be my guess.
Breechblock left closeup. While difficult to see in this photo, the underside of the conversion toggle includes a spring loaded buffer of sorts, that I think contributes to the ability to operate this system as a blowback when combined with the difference in the toggle hinge pin locations, rather than locked breech toggle like the original design.
The right side of the breechblocks. Notice that the original block is round on the bottom and the conversion is flat... probably for proper feeding and clearance working with a .22 magazine.
Notice how the rear end of the rear toggle has been substantially ground down to allow opening of the toggle without moving the upper receiver. This accounts for a major reduction of resistance during the blowback operation.
My next installment should include better photos of the underside of the toggles to show the elaborate spring loaded buffer that was created on the conversion.
I hope this photos essay has been capturing your interest and has been as thought provoking for some of you as it has been for me to do this study.