Here is my custom built HPA AEP.
This is DIY project, with a whole lot of quick and dirty solutions, which seem to work rather well so far.
The main point was to build the ultimate secondary with the following points:
-as or more silent than my Mk23
-as accurate as my Mk23
-smaller than my Mk23
-better trigger than my Mk23
+fullauto capability
+built in tracer
Ultimately I faild to reach these goals, but it was a really fun adventure, and the result filling holes in my armoury I didn’t even know I had…
Before you read further, you HAVE to watch the video of Trung The Maker, I used his files and advices to base my build on.
Video link: https://youtu.be/TlQtNbUG3Fg?si=P0goc9czL3tn-K-t
My build is based on a Cyma SAI Glock, but in theory works with any similar AEP.
As you see Polarstar FCU, universal plug board, battery and wires fits barely below the barrel.
I had to shorten all wires to save room, but managed to make room for UV led’s wires, those run straight from the FCU, to the chamber. Since it’s open bolt, the tracer bb getting charged when loading in the chamber.
For the printed pieces I went straight for MJF. Had to mod things on the engine too, other than fitting the link for the AEP nozzle, the nozzle of the engine is drilled up to fit a brass tube. This tube guides the nozzle when loading and also reduces any airleak between the AEP cylinder head and engine nozzle.
Even with the longer 200mm inner barrel, the system needed 200psi to reach just 1.3J on .40. That was the result of smaller engine volume, what is not an issue if the air dosn’s get wasted to move the AEP nozzle and fill the longer route to the chamber.
To solve this I got CNC’d a new front piece for the engine with higher internal volume. Result of this I managed to reduce the pressure to 140psi to get 1.3J.
That is sort of acceptable, but the high psi and less usefull volume of suppressor results in louder muzzle report than what I would be happy with.
For the trigger switch I used a microswitch inside the trigger itself, I can’t take a photo of it, it’s literally built into the trigger… Fullauto also works properly, it’s usefull time to time, but more of a fun factor.
In the hop chamber, I drilled two holes to the side to fit 2mm UV leds and filled the top with epoxi to give it a TDC screw. I use one of my own inner barrels cut back to 200mm and a Begadi aep rubber. The accuracy this way is aceptable, it’s not an awesome level, dosn’t match my Mk, but it shoots better than most aegs.
The final results is not on the level of a sniper secondary, but in full CQB or mostly urban fields this system ROCKS. With this trigger the speed you can engage targets and the relative silent working results in a highly effective CQB tool, before I didn’t even know I needed this, but now this is my favourite room clearer.
On the long run I plan to CNC a custom nozzle and laser cut the nozzle link mechanism.
If you have ideal or questions regard the build let me know!