Originally Posted by Moon

Been busy.
Looks like I have it figured out.
I changed out the firing pin for an "extended firing pin" from Apex.
The gun was still experiencing dead snaps on D/A. S/A it was working perfectly.
As stated before the strain screw came from the factory tightened all the way in. I thought I would try to get a shim in between the screw and the mainspring. I was going about it wrong trying to wedge something in there with the strain screw removed. Then it dawned on me to try another tack. Leaving the strain screw all the way in I placed a plastic piece between the mainspring and the frame up above the strain screw.
Then backing off the screw. The mainspring remained far enough apart for me to easily place a small brass shim where the strain screw contacts the mainspring. Then retighten the strain screw and TA DA!
It worked.
Took the gun to the range just now. Perfect operation for 50rds fired.
D/A trigger pull is stiffer than it was but not unbearable. With use it'll slick up even more.

Just for learning purposes I did try to fire 22LR round in the 648.
It would not fire any of them. It appeared the 22LR round lays too low in the firing chamber when the gun is held in the normal level firing position.
The firing pin strikes just a tad too high on the 22lr rim.
Maybe if I held the gun upside down it might fire? LOL