Customizing the 1911: countersink and flush cut slide stop pin

Countersunk and flush cut slide stop pins have become common on custom 1911s over the past few years.  This simple modification adds a distinctive touch to a 1911 frame.

For reference purposes, a schematic of a 1911 pistol can be found here.

Before we get working, take a few minutes to read’s disclaimer:

Warning:  The contents of are produced for informational purposes only and should be performed by competent gunsmiths only. and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.

Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.

I ordered the following tools from Brownells to complete this project:


After the frame is completely disassembled, the area surrounding the slide stop hole needs to be inspected.  If the serial number or marking is too close to the hole, the frame may not be a candidate for a countersunk slide stop pin hole.


Set up for the actual countersink operation is fairly straight forward.  This could be performed on a mill or drill press (I’m convinced a hand drill would be fine but wouldn’t recommend trying it).  I align the frame underneath the mill by placing a gauge pin that fits the hole in the mill’s chuck.  The pin is lowered so it passes through the hole and while the pin is still in the frame, the frame is clamped into place.


With a 100 degree single flute countersink in the chuck I verify alignment.


A shallow plunge into the frame and the counter sink is formed.  The single flute counter sinks leave a smooth, chatter free finish.


A close up look at the cutter.


Trimming the slide stop pin is a little more complicated.  You could simply file or mill off the excess length, however, a lathe will give superior results.  To hold the slide stop in the lathe I’ll need to make a fixture.  I chuck up some scrap aluminum bar stock and turn down a small section about .700″ long for the fixture.


I drill a hole the same size as the slide stop pin.


Then part and face the small section of the fixture.

countersink-1911-slide-stop-pin-10Finally I drill and tap a hole for a set screw.


The fixture to hold my slide stop in the lathe is complete.  Let’s cut it down!


I dial the slide stop in on a set-tru three jaw chuck.


The pin is cut to length, in this case, so it remains slightly below the surface of the right side of the frame of the pistol when it is reassembled.


Looks great, doesn’t it?

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