The point of no return... (Sticky Trigger)
With this being our third article on the "Sticky Trigger" phenomenon, it's almost deserving of it's own series on this blog; if it were not for the fact that the last article should have been the last we heard about the Sticky Trigger for good. Alas, here we are, because the Sticky Trigger has returned, this time, with the magazine removed from the pistol, something we've not seen before until now.
From our previous articles on this subject, we know that sticky trigger usually would occur because of the magazine gas router height being too high which prevented correct return of the nozzle back to a neutral position. The solution for this was to reduce the router height for the nozzle to safely pass through. The other common cause was that the nozzle loader would catch the bottom of the hop rubber and be held in place due to friction as it returned to neutral, again, this was solved by modifying the nozzle loader or adding some lubricant to the loader itself. In both of these cases, the magazine was inserted which made it easier to identify where the problem was and how to solve it. However, recently whilst installing a new hop up bucking (the TNT TR Hop Rubber), we encountered the sticky trigger, with the magazine ejected.
Our first thought was to go over one of the solutions we already knew about, so we checked the nozzle loader to see if it was being caught, and this is where we noticed that the nozzle itself was instead getting stuck in the hop up rubber. When pulling the trigger back to its full extension, the nozzle was being shoved in to the hop rubber by the trigger arms and the tighter tolerances of the new TNT hop rubber lip were holding the nozzle in place, preventing the nozzle from returning to neutral and causing the Sticky Trigger.
We know from experience that lubricating the nozzle would solve the friction issue, but we also know that introducing lubrication to the hop rubber via the nozzle would cause hop up issues. So lubrication was out of the question here, and we had to look elsewhere to solve this issue without replacing the TNT hop rubber (because we actually wanted to use it!).
With the bucking holding on to the nozzle with the grip of a rock climber, we needed to find a way to beat out it's hold on the nozzle or at least pull the nozzle back before the rubber got a grip on it. After giving the nozzle a nudge, it jumped back in to neutral position, pulled by the tension of the nozzle return spring. This spring would be the key, and we were going to stretch that spring.
After removing the hop up / barrel assembly, we could start to take a closer look at the Nozzle Return Spring (shown in the gallery below).
Now that we knew what the Nozzle Return Spring (NRS) looks like and where it's located, we needed to remove the nozzle housing from the slide so that we could access the NRS.
Removing the nozzle housing from the slide
Remove the nozzle housing, following these steps: 1. Lay the slide top down on a flat surface.
2. Locate the 4 tab recesses (2 on each side of the nozzle housing).
3. Using a small flat head screwdriver, or a blade edge, leverage the housing away from the slide wall using the recessed tabs (see image 1 below).
4. Using your finger, press against the outer flange of the nozzle housing whilst leveraging the housing from step 3 (see image 2 below).
5. The nozzle housing should lift up and away from the slide, remove it freely from here (see image 3 below). Note: Be careful when removing the housing, as the NRS may shoot out from its position at the top of the housing.
With the nozzle housing removed, we could now get to the NRS, which is located on the top of the nozzle housing. The NRS will be held in place by the NRS spring guide, which can be gently lifted out from one side whilst holding the spring in place to prevent it from flying off.
With the NRS removed, we are now able to make the change that we've come this far for, we're going to stretch the spring. Science The quick science behind this, is that by stretching the spring, the spring is held under more tension when its compacted and returned to the nozzle housing. This increased tension will help pull the nozzle back out of the hop rubber's grip as the spring retains and releases more energy as it uncoils to its new stretched length. Taking a quick measurement, the stock NRS in our sample TM MK23 measures to 69mm x 3.5mm, and we were going to stretch it out to around 104mm in length. You are free to stretch it beyond this length if you feel its needed, but 104mm provided enough tension to solve our issue. To stretch the NRS, just pull it from each side.
With the NRS stretched to its new length, insert the spring guide back in through the spring.
The next bit can be a bit tricky, and can result in the spring flying off if you lose your hold on the spring during re-assembly, so try to work in a confined area so you have an easier time finding the spring if it happens to fly off.
Taking the nozzle housing home
The nozzle housing and NRS can be reassembled as follows:
1. With the NRS placed on the spring guide, locate the spring guide socket found on the built up side of the nozzle housing (see the image below), insert the spring guide in to this socket first.
2. With the spring guide in the socket, keep tension on the spring and lower the other side of the spring guide down in to the guide recess.
3. Keeping tension on spring guide (use a finger to pin the middle of the guide down), turn the nozzle housing around and lower it back in to the slide.
4. Do this by placing the rear of the nozzle housing down in to the slide first then lowering it in evenly, it should click in to place when the tabs align.
With the hard bit done, we were on the home stretch. After returning the nozzle housing back to the slide, we re-assembled the rest of the pistol, making sure first that the magazine was ejected; we gave the trigger a pull. Success.
Stickiness be gone!
The nozzle was driven forward by the trigger arms and then returned quickly back to the neutral position with no resistance, resetting the trigger back to neutral with it.
Whilst it was unfortunate that we encountered another case of sticky trigger, we were glad that it happened so that we were given the chance to try and fix it.
One of the things we considered during this was whether we should try to locate a stronger spring that could be installed in place of the stock spring and what that might do for the trigger reset as a positive modification, but for now, we were just happy to solve our immediate issue. It's something we could explore in the future however!
With the Sticky Trigger resolved, we were now free to carry on with our review of the TNT TR bucking, but that's for another time and article! We hope this helps solve your issue if you encounter it!