Editors note: This article should be considered deprecated and exists for historical purposes only. An updated article covering current standards can be found here.
One point of contention with many regarding KWA AEG’s is their use of a proprietary air nozzle. While it is claimed that most KWA internals are Tokyo Marui spec – this is only partially true. With the advent of the newer 3GX gearbox – itself an evolution of the 2GX – KWA has departed even farther from the TM spec design and many internal parts are unique and proprietary enough to cause issues should you try to source alternatives.
My personal experience with most KWA’s is that they have less than satisfactory air compression or suffer from FPS loss out of the box. Your mileage may vary, of course. We have previously covered one technique to dealing with low FPS in KWA AEG’s here. With regard to specific air seal parts, the cylinder head to cylinder fitment is usually quite good and can even be extremely tight should you use an aftermarket cylinder. Guarder cylinders in particular are very tight and care must be taken not to cut the cylinder head o-ring when installing one. It should be noted that most highly knowledgeable experts on KWA recommend replacing all the internal o-rings as a matter of course due to their quality (or lack thereof.) Experience leads me to tend to concur and as such I will throw in higher quality o-rings as soon as I crack open a new gearbox.
The air nozzle on the 2GX and 3GX gearboxes is a slightly strange and proprietary design. It does not feature an internal o-ring to help further aid in air seal. It is also made of metal and features a spline on top which is presumably for indexing into the hop up chamber – but even with this absent, the nozzle does not rotate due to the stabilization wedges acting against the tappet plate. KWA has yet to inform me as to the specific advantages their air nozzle offers, despite several emails. Conventional internet wisdom will tell you that in order to swap the air nozzle out with TM spec, you will also need to replace the cylinder head, tappet plate, hop up chamber, and of course the air nozzle. All of this in order to achieve the usual objective of gaining an air nozzle with an internal o-ring and to bring things to “TM Spec.”
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Unfortunately the KWA air nozzle is not quite a standard Version 2 gearbox length. Obviously installing too short of an air nozzle will cause extreme FPS loss as the air nozzle is unable to create a good seal against the hop up bucking. Too long will create feeding issues. The trick then is finding one that is “just right.”
I have found that a Real Sword AK Version 3 air nozzle is approximately the same length as the KWA air nozzle. It is also a 95% drop in fit without requiring you to purchase any additional parts. It should be noted that the Real Sword nozzle is not a true Version 3 TM spec either. It’s actually a touch longer than most TM spec Ver. 3 AK air nozzles you will find out there. But for our purposes, that works out really well when you’re going to drop it into a KWA.
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Firstly, you will need to ensure it fits inside your hop up chamber. It may be a little too tight – I tried this across 4 different Real Sword air nozzles and found this to be the case with all of them. If this is the case, then you simply take a bit of fine grit sandpaper and work down the shoulder a bit until the air nozzle fits. As you can see from the above photo, the Real Sword air nozzle has a higher “shoulder” than the KWA one (pictured on right). This is all that really prevents the RS air nozzle from seating fully into the hop up chamber.
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Second, check the fitment of the air nozzle to the cylinder head. KWA once again uses some slightly off-spec parts here – you will probably notice the air nozzle fits pretty tight to the cylinder head. The brass shaft the air nozzle rides on is slightly larger diameter than a typical Ver. 2 or Ver. 3 design. As such, you simply have to take your bit of fine grit sandpaper and give it a good polish.
All told, it takes about 5 minutes of really minor sanding and fitting to get this to work properly. Even better, you do not have to replace the cylinder head, tappet plate, or hop up chamber to do this. After installing the new air nozzle I gained about 20 FPS on my setup! I’ve function tested for just over 1000 rounds and so far it has performed flawlessly and maintained FPS. Ideally I will get to test this out further at an actual OP so I can report back on how well it’s working. So far I’m pretty happy with the performance gains though.
And if you’re interested in the custom KWA RM4 build, you can check it out here.