DIY Sig P938 Rail & 8rd Magazine

    My EDC is a Sig Sauer P938. I like the size and with the factory 7rd extended magazine it feels like a compact.

    However there is room for improvement. Sig Sauer has a trigger guard laser that you can buy and attach to the P238 or P938. It works for both guns.


    I am not a fan of lasers as much as I am a fan of flashlights. So I got a broken laser unit to make into a rail for a light.  I sent the broken Sig laser to my friend Alex to reverse engineer and draw in 3D. I told him redraw it and remove the laser portion but replace it with a picatinny rail. Here is the drawing of that rail.

    P938 rail


    He drew it up for me and I printed it through Shapeways.

    For the light I went with a Viridian C5L as that was the smallest rail mounted green laser with white light that I could find.



    Next modification was due to playing with a Sig Sauer P290 Liberty Edition. It comes with an extended magazine that holds eight rounds. Looking at the magazine, it has similar dimensions as the P938 magazine. I took one and shoved it into the P938 and it fit.

    You can see the factory P938 7 round magazine next to the P290 8 round magazine.



    The only issue was the magazine notch was not the same. I bought a P290 extended magazine and cut a new mag notch with a dremel. Not perfect looking but completely functional. It will load and chamber rounds. Look at the magazine on the right, the two small square holes is the factory notches for the P290 and the cut above is for the P938.



    The P290 magazine is not that much longer than the P938 magazine and you can hold one extra round. Now I can carry 8+1 in my Sig P938.



    The P290 extended magazine has a large pinky extension. I had to chop the top of the plastic extension off a bit for the magazine to seat properly. Otherwise the extension would hit the bottom of the pistol grip before seating.


    The larger P290 extension makes for a more comfortable grip.



    You do not have to use the P290 extension if you so desire and the magazine body acts as a pinky extension.



    Below is a factory 7 round P938 magazine with pinky extension removed.DSC_0150 DSC_0149

    If you so desire, you can use the P938 pinky extension and use it on the P290 magazine. Since the floor plates of the two magazines are different, the P938 extension does not protrude past the bottom of the P290 magazine.


    Of course all of this does not matter if I cannot carry it. So my friend at Dark Star Gear made me a custom kydex IWB holster for this setup.


    Nicholas C

    Steadicam Gun Operator
    Night Vision & Thermal Aficionado
    Flashlight/Laser Enthusiast
    USPSA competitor

    Any questions please email him at [email protected]