Adjusting the KWA Variable Performance System

KWA’s Variable Performance System (VPS) is a unique method of fine tuning the FPS output on your AEG 2.5 series rifle. It also functions as a quick-change spring guide, and unlike traditional M4’s with such systems, removal of the gearbox is not necessary to swap springs out.

The KWA VPS typically has a 50~ FPS adjustment range, and comes equipped from the factory with a M120 equivalent spring. The primary advantage of this system is you can easily configure your FPS output to meet most CQB or field site limits, which makes the VPS system a versatile multi-role setup.

The VPS system is currently found in the following KWA models:

How to Adjust the VPS guide

One of the questions I’m often asked by owners of the KWA VPS series rifles is: “How do you adjust the spring guide?”

This is actually incredibly easy to do, and requires only two tools (or one) and a few minutes of your time.

Step 1.

Remove the buttplate from the stock. Insert a #2 Phillips screwdriver into the buffer tube. You are looking for a black screw and half-moon shaped plate inside the buffer tube. Remove the screw and the plate will come out.

Step 2.

If purchased new, your rifle would have come with a long T-handle 2.5mm hex key. After removing the screw and retainer plate, insert the 2.5mm hex key into the back of the spring guide until you feel it index into place.

Shown with buttstock removed. This is not necessary for adjusting the VPS guide.

Step 3.

Rotating the hex key clockwise will increase FPS. Rotating counter-clockwise will decrease FPS.

Generally speaking, most rifles will have around a 50 FPS adjustment range. Some factors, such as compression, aftermarket upgrades, etc. may change this value slightly. I usually find that most guns can be made CQB legal (under 350 FPS) with the guide adjusted all the way in. Field legal velocities are usually found by adjusting the guide to the 1/2 – 3/4 mark. Obviously you will need access to a chronograph to properly measure FPS and Joule outputs with your given BB weight.

…If you don’t have a hex key

There is an alternative method of adjusting the spring guide if you do not have a 2.5mm hex key on hand or find that your key is too short to reach inside the spring guide.

After removing the Phillips screw and retainer plate, you can slide the buffer tube off the receiver extension.

The VPS spring guide can now be accessed. Simply press it in slightly with the palm of your hand and rotate it to the left and it will easily slide out. You can now manually adjust the spring guide with your fingers. Again, clockwise will increase FPS. Rotating counter-clockwise will decrease FPS.

When reattaching the buffer tube, care must be taken to install the retainer plate correctly and not pinch the wires. It technically only goes in one way, as it has a pair of square lugs that index into some square notches inside the buffer tube.

Maintenance of the VPS

Under normal operation the VPS requires no real maintenance. There is no real need to lubricate the components, spring, or spring guide. On rifles with high round counts, I recommend periodically checking the set screw on the guide and ensuring it is securely fastened. You can also use thread locker (blue Loctite is best) on these components for extra peace of mind. Do not use thread locker on the main threaded shaft of the spring guide.

Make sure that you always have the roll pin installed in the end of the brass housing. This prevents the adjustment shaft from coming out completely.

Aftermarket Springs

The VPS is compatible with all brands of AEG aftermarket springs. FPS output will obviously be affected by the spring strength used, internal compression and other factors. I have tested the system successfully with springs as powerful as an SP170 without failure. The VPS also lends itself well to use in DSG conversions as you can easily increase FPS without having to use spring spacers.

Converting the RM4 AEG 3.0 (recoil version)

The modern versatility of the current generation KWA platforms allows for easy conversion of the recoil-based RM4 AEG 3.0 to the VPS system should the end user desire it. The VPS system uses a different buffer tube than the RM4, so you will need to keep in mind that your RM4 buffer tube is not compatible.

The complete KWA VPS conversion kit.

Conversion requires that you remove the recoil assembly from your RM4 and both springs.

  1. Remove the wire channel cover plate by removing all four phillips screws to expose the wiring. You will want to cut away the heat shrink around the two quick-connects so you can remove the tail end of the wire harness.
  2. Remove the small socket cap screw that goes through the sling plate.
  3. The next step is to remove the gearbox from the receiver. Start by removing the motor grip plate (the small allen screws – do not remove the large brass adjustment screw in the center).
  4. Drift out the pin above the trigger – generally you push it out from left to right.
  5. Back out the large receiver push pin. It is a captured design, so it doesn’t come all the way out.
  6. Now you can remove the gearbox from the lower. You do not need to remove the magazine release or selector switches.
  7. Once you have the gearbox free, you can remove the old buffer tube. Loosen the castle nut on the buffer tube. Slide the sling plate back until it clears the squared off sides of the buffer tube. You can now unthread the buffer tube from the receiver.
Keep the wires pulled down when threading in the VM4 receiver extension.

Reassembly

  1. Reinstall your gearbox, ensuring the selector plate is properly aligned and all 3 selector positions work properly. Route the wire harness through the small square slot where the buffer tube threads sit.
  2. You are now ready to thread in the VM4 receiver extension. The extension also functions as the housing for the VPS spring guide. Careful note should be taken to prevent the extension from cutting the wiring when threading it into the receiver. The VPS extension does not thread completely flush into the receiver. A small portion of threads is left exposed to provide support for the sling plate, which also helps prevent the extension from rotating in the receiver.
  3. Reinstall the sling plate socket cap screw.
  4. Reattach your wiring pigtail to the wires coming from the gearbox. Red to red, black to black. Be sure to reapply heat shrink over the bare connections otherwise you will cause a short.
  5. Slide the KM4 buffer tube over the VPS extension. Then install the retainer plate and screw with the split washer. You can now reattach your buttstock.

VM4 conversion kits can be purchased through Tactical Parts or contact the KWA Pro Shop for assistance.

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