TM PSG-1 Ultimate Upgrade Guide

The Tokyo Marui PSG-1.
Probably one of the rarest AEGs you'll see (or not) on the skirmish field.

It uses a unique v4 gearbox with many advantages and cool features and can be upgraded to Bolt-Action levels of performance.
There are two main problems with these beasts:
The parts are very hard to find and the trigger feels horrible!


With a little digging and delving, I've managed to source every upgrade part I wanted for my own build.
Thanks to a little inspiration from Luke Mosley aka SkyDiver, I've worked out a way to get rid of the soft, spongy trigger by hooking up a BTC Chimera MOSFET.

I'll give you guys a quick run-down of all the parts I've used for the build and then take you through the steps required to install the Chimera.

For the externals:
TM PSG-1 of course :)
G&G Magnesium Receiver set
G&G Steel Stock Screws
G&G Extended PSG-1 Top Rail
PDI Chamber Block
PDI Fluted Outer Barrel
Custom Made (to the real dimensions) PSG-1 Suppressor (LCsEngineering)
G&G Rail
Magpul XTM2 Covers
Magpul AFG
Genuine Harris Bipod
UTG Low Scope Mounts
UTG Scope (will update with exact model)
Scope Spirit Level (will update with exact model)
Bed-liner sprayed grip

Here it is centre-stage:
 


And for the internals:
Systema 300% Bore-Up Kit, which includes:
-Chromoly Steel gears (36.9:1)
-300% Spring
-Bearing Spring Guide
-Steel Bore-Up Cylinder Head
-Mushroom Piston Head & O-Ring
-Steel Bore-Up Cylinder
-Bore-Up Nozzle
-Aluminium 19T Piston
Systema Steel Top Plate
TerminusX 6mm Tungsten Carbide Bushings (out of production, I'd recommend Prometheus or FLT now)
Airsoft Engineer Custom Steel ARL
Plus all of the usual shimming and tuning
Hand made Medium Motor:
-14TPA - 20AWG (0.8mm Dia)
-N42 Neo Magnets
-Helical Armature
-Vented Shell
-Silver Vertical Brushes
-Strong Brush Springs
-Over-sized support bearings
-Epoxy-potted Windings and comm-tabs
-HMP Soldered comm-tabs
-Balanced
-Shimmed
-Trued on the Comm Lathe
BTC Chimera v2
Genuine Deans Ultra connector
EdGI 650mm 5.98 ID Barrel with 6mm Square-Cut Window
R-Hop
Prometheus Purple Hop Rubber

The idea here was to create something with a huge amount of air output with a very tight barrel to maximise the energy bias.
Using a barrel as tight as this doesn't create anywhere near the issues most people tend to think it will and you really don't need to clean them that often if you simply take care of the rifle. Using high quality ammo is essential but that's a discussion for another time ;)

I wanted as much of that air to be used in propelling the BB out of the barrel as possible. This will allow the use of a lighter spring (effectively an M150, though I did cut it down by a couple of coils) which will put less stress on the gearbox internals - I want this build to last forever as some of the parts (the gears especially) basically don't exist any more.
You could even run this build on the stock gears and achieve 500fps and still have it last a good while.

Please don't hesitate to ask or PM me with questions about the build, why I chose certain components or even help with sourcing parts :)

Installing the BTC Chimera was probably the part I looked forward to the most!
I'd already completed the external build and about half of the internals but was running it on an Extreme-Fire SW-Cheetah-2N MOSFET that hooked into the existing trigger mech (I stripped out the electrical safety).
This meant that the trigger still had that awful, soft-spongy feel to it so I didn't use the gun as often as I'd like.

Installing the Chimera solves everything though :)

To get it in the gun, a little modification was required to the trigger mech so there was space to glue in the required Microswitches.
I opted to install the switches inside the switch assembly instead of inside the gearbox shell so that the wiring could be decoupled from the gearbox.
This makes it easier to work on, tidier and allows for future work to be carried out on the gearbox without wires getting in the way.

I roughly lined up where the switches would have to go on either half of the assembly.
For the trigger side, we have to use the secondary trigger lever so that spring tension will still be applied to the trigger to reset it after each shot.
This is because the trigger level itself does not have it's own spring.
Lining up the switch was pretty easy here, simply mark the resting and final position of the secondary lever and position the switch so that it is fully depressed in the final position and just untouched when the lever is back.
I used the large milling bit for my Dremel to take away any obstructing plastic so the switch could be positioned correctly.

For the Cutoff Lever switch, it was a tad trickier.
I initially positioned the switch so it sat very closely over the lever, which works fine when the gear activate the Cutoff.
The problem came when I tested the manual de-cocking function, which extends the lever further than the gears would to unlock the ARL.
This caused the lever to move fully above the switch, allowing it to spring out and block the lever's return.

No good at all.

Moving the switch a little higher solved everything.
The cutoff lever still activates the switch when operated by the gears but does not move above it when manually pushed.

Once the positions were sorted and channels were dremeled for the wires, I soldered some thin wires to the bottom tabs of the switches and glued them in place with a tiny dab of superglue.
Be sure to clean the area thoroughly with IsoPropyl Alcohol before doing this and ensure no glue enters the switch.
After that, a little epoxy was used to hold them in place permanently and protect the wires from flexing and pulling the switches :)
 

There are now four wires protruding from the front of the assembled trigger unit.
Choose one from each switch and label it 'Ground'. It doesn't matter which ones - you can even solder them together to form one wire.
This line will be routed directly to the Ground pin on the Chimera.

The other two wires will go to the trigger pin and cutoff pin respectively.
Lastly, we'll need to take the fire-selector pin and take that to Ground as well.
This negates the need for installing a third microswitch to detect the selector plate position. Since there are only Safety and Semi-Auto positions and the safety manually blocks the trigger, this isn't an issue. We just have to program both selector positions to Semi-Auto Only in the Chimera.

I've soldered the wires on to the corresponding wires of the data cable that comes with the Chimera to avoid having to solder directly to the board (pictures to follow).

And that's basically it :)
Just reinstall the gearbox and route the wires through the stock with your connector of choice (Gotta be Deans) and you're done!

Let me know if you have any questions at all, I've really enjoyed building this rifle and would love to see more of it's kind on the field :)