This article explains how to replace the ugly plastic CO2 tightening knob on the Umarex Walther PPK/s with a less obtrusive screw. However, please remember that CO2 and airguns are potentially dangerous. If you attempt any modification you may end up with a pistol that is unusable, unreliable or even dangerous. So, don’t undertake any modification unless you understand it fully and are confident that you have the necessary skills to complete it safely. If in doubt, get advice from an expert. I accept no responsibility for any damage, injuries or aggravation which may be caused if you decide to try this mod.
I have owned two Umarex Walther PPK/S, and they are generally great pistols (read the review here). However, in my opinion the appearance of this replica is spoiled by the CO2 tightening/piercing knob which projects below the butt. On early models this is a huge plastic wing nut. On later models it’s a slightly smaller plastic tab. On both it looks kind of stupid.
Fortunately, replacing the plastic tab with something less obtrusive is simple and doesn’t require many tools or much technical expertise. The simplest solution is to simply cut off the plastic knob with a hacksaw and then cut a slot in the end of the remaining threaded stem, which allows tightening by using a screwdriver in the slot. However I tried this on my first PPK/S and I found that so much force is required to tighten with a screwdriver that the slot in the mild steel stem quickly opened up and became unusable. What I wanted was a more permanent solution.
To do this job you’ll need the following:
A small hacksaw.
A small (approx. 1mm dia) drift.
A ruler or vernier caliper for measurement.
A suitable screw and nut to replace the plastic stem and knob.
Before starting the work: MAKE SURE THERE IS NO CO2 IN THE PISTOL! Otherwise, this job will get very exciting, very briefly as you remove the pins that retain the CO2 tightening parts in place. No kidding!
Once you’re sure there is no CO2 in the gun, start by removing the left grip and the magazine. Then you need to drift out the two small diameter pins which hold in place the plastic cover which keeps the CO2 tightening stem in place. To do this you’ll have to remove the right grip by removing the single screw which holds it in place. Be careful not to lose the safety catch spring. Once the pins are out, replace the right grip to protect the safety catch mechanism.
Once the pins are removed, you can take off the black plastic cover and remove the tightening stem, retaining nut and knob. The pistol should now look like this.
The next step is to find a suitable screw and nut to replace the plastic stem and knob. You can use anything that will fit – I happened to find a stainless steel socket-head screw and a matching nut in my toolbox, so I used those.
Then, measure the excess to find out how much you need to cut off.
A tip if you’re cutting anything with a thread – before you start, thread a nut on above the area where you intend to cut. The cutting will inevitably damage the thread, but if you have a nut in place, when you unscrew it, it will help to re-make the thread.
Once the excess part of the screw shaft is cut off with a hacksaw, file and sand the cut end until it is smooth and flat – this is important, otherwise the CO2 cartridge may slip off the end of the screw when you tighten it. Then, put the new screw and nut in place, replace the plastic cover and the two pins which hold it in place. Now try tightening to hold an empty CO2 in place.
If the new screw holds an empty CO2 securely in place, you can try loading a full one. Hold the CO2 cartridge firmly in place with your thumb as you tighten to stop it twisting out of the way.
And that’s it, job done. Problems? The end of the original tightening stem is dished to fit the bottom of the CO2. Your replacement won’t be. Potentially, the CO2 can slip off the end of the screw as you’re tightening. So, you do need to flatten off the cut end of the new screw as much as possible and hold the CO2 cartridge firmly in place as you tighten the screw. You also need to remember to bring a suitable allen key when you want to shoot the PPK/S.
I am not recommending that you do this mod to your Umarex PPK/S, though I do think that the modified pistol looks much better. After the mod my PPK/S was still as reliable and powerful as before. However, as noted at the start of the article, undertaking any modification to an air pistol is potentially dangerous, so please don’t do this unless you are certain that you can complete the work safely. One of the nice things about this mod is that it’s completely reversable – if you don’t like using a screw for CO2 tightening, just replace the tab, stem and nut which you removed and you’ll be back to standard.