Parashooter "The front counterbore is shallow because it is in the leaf spring, not the sight base - if deeper it would leave little or no thickness below the screw head."
That explains a lot. Never have seen one of these in person. I think the manual drawing adds to the confusion. It looks like the spring needs to be rotated and looking at Boomer's photo the spring is dove tailed and slides into the base from the front?
They may have had plus or minus .015" on the head thickness tolerance as no problem if it is thicker.

Maybe the thicker head is to help the one doing the assembly to keep them separate? Putting the short screw up front may have damaged the barrel and or screw, if it even engages.


Looked at Parashooter's drawings again, they are from 2 different pages correct? The front of the sight is on the left and the front of spring is on the right? If so a lot less confusing.