By William O. Milne
Gun Club of America SilverPLUS Member
AGI Professional Gunsmithing Graduate
DBI William Oliver Gunsmith
A customer showed up at my shop with a Kahr CW45 all locked up, slide stop pin in hand, and a spent cartridge in the chamber. After tapping on it with a wooden mallet while working the slide, I managed to get the pin back in and eject the cartridge. During take-down, the problem was shown to me by the customer. The slide stop spring retaining screw was loose, although he had tightened it several times when the pin kept working out. On further examination, the plastic hole that the #2-56 machine thread screw was supposed to thread into was stripped out.
A call to Kahr’s service department produced this information:
- The 5 year warranty covers the original customer only
- The determination as to whether the damage was a factory defect would not be determined on the phone, it had to be examined by a factory representative
- The usual fix was a frame replacement at a cost of $250.00, plus $65.00 for an hour’s labor.
Normal engineering practice would be to reinforce the area where a fastener goes when it is under stress. In this case a .45 ACP goes bang, driving the barrel and slide back against the slide stop pin. The shock is transmitted to the #2-56 retaining screw from the slide stop pin to the spring and washer. The spring is wound counter clockwise around the screw so a hit by the pin on the spring and the movement of the tail upwards at the last shot tends to loosen the screw.
A quick google search produced a number of people looking for a solution to the same problem. I first tried the superglue method one person had success with, to no avail. The screw would not tighten enough and stripped again. The only option left was to reinforce the hole.
The first step was to make a barrel or stem nut. There is not much room beside the pin hole, so I settled on a diameter of .100 in. for the stem. Its through hole is drilled .067 in. (#51) for a #2-56 thread. The small tapered flange will retain the stem nut in the frame. The overall length was decided to be .190 in. A short step down in diameter to .096 in. for the first .050 in. of the stem nut allows easy insertion in the frame after the old screw hole is carefully opened up to .096 in. (#41).
I used my Foredom tool and a small round burr to chamfer the hole inside the frame just enough to seat the head of the stem nut flush and out of the way of the barrel lug. Start the stem on the inside with a set of needle nose pliers, then finish with a pair of regular pliers to pinch the nut and frame till the head of the nut is seated flush.
A little dab of BLUE Loctite on the screw will keep it from working loose. Tighten the screw carefully, just right, not too tight, to the point the spring snaps into the groove in the slide stop pin when it is seated. Insert the pin slow and carefully to prevent bending the spring tail. The end of the spring must ride above the notch shelf on the pin. It is very easy to damage the spring. Properly installed, the spring does two jobs: it holds the slide stop in its place and holds the stop down until the empty mag overcomes it and locks the slide open.