Nice writeup. Did you trim/sand anything off the outside of the shell? From the last picture you took, it almost seems the blaster IS telling you to "shoot anyone in the face or eyes" ... Am I missing something here?
You should check if that part is even necessary to operate the gun. It's possible that the part is a redundant safety mechanism that you won't need like the magazine-lock or the boltsled-lock on the Longshot.
I can say for sure it IS necessary, as it is the piece that the spring pushes against in order to drive the plunger rod down the tube.