Here are some pictures. I found that there was a very small screw that could be removed via a hole in the locking block when the firing pin was in the firing position. The screw attached to the firing pin, but did not release the firing pin from the bolt, nor help remove the bolt at all. the only difference I can tell is that the firing pin now rotates within the bolt.
The pin that holds the locking block to the bolt is just to the left of the firing pin screw hole. With the bolt completely open, it is about a half inch away from the punch hole. I can put a punch completely through the receiver while moving the bolt from fully opened to fully closed. There are no other punch holes in the receiver.
The restriction on moving the bolt farther to the rear is the duct cover nut. I do not see how it could be removed, but maybe it can. I certainly don't want to mar it trying.