After completing the A&K Masada PolarStar Fusion Engine Conversion, there have been several requests to see if a Magpul PTS Masada could be converted to use a Fusion Engine. The Magpul PTS Masada uses a proprietary gearbox, that is like a hybrid between a V2 and V3 gearbox. It has the basic dimensions of a V2 gearbox, but it utilizes a motor cage like a V3. Also the selector plate on the PTS is custom and the selector switch gears are mounted in unique location (not using standard V2 through-holes). Joe Pane was nice (brave?) enough to send me his Magpul PTS Masada to be converted to a PolarStar Fusion Engine (FE). The gearbox had cracked and it was essentially impossible to replace, so putting an FE seemed to be the appropriate action!
The Fusion Engine did not drop into the PTS Masada as easily as the A&K Masada. Especially in the grip area, the geometry was quite a bit different, so a bit of machining was needed to have the Fusion Engine fit in the grip properly. The grip base on the FE was too large, so it had to be shaved down so the FE can align properly with the nozzle and the trigger location.
To mount the Fusion Engine, a bracket was made to support the back of the FE, while the standard holes in the magwell could be reused to attach the front of the FE. By cutting a slot on the stock mounting brace, the stock could be used to lock the FE brace in place, removing the need to have any extra holes drilled into the lower receiver. This back mounting method worked out very nicely and it holds the FE very securely. The front of the FE was mounted by reusing the two magwell holes already in place. It turns out that the PTS has a small gearbox alignment nub, and this nub works as the perfect shim to align the FE nozzle with the hopup. The FE sits on top of this nub, and is held in place by the screws, one on each side. Since the nub is centered, adjusting the tension on either the left or right mounting screw can be used to minutely shift the FE nozzle left or right, so it can be perfectly centered for the hopup.
The other challenge was to support the fire selector functionality. The PTS uses a geared mechanism with large gears mounted on the gearbox. The gears synchronize the left and right fire select switches. The left side gear has a cam which is used to push/pull the selector plate to engage the safety and the semi/full auto modes. Unfortunately the PTS does not use the standard through-hole on the V2 gearbox for the select fire gear assembly. It has it’s own through-hole which is just slightly lower than the standard location. So a new through-hole had to be drilled so the gears would align properly to operate the selector plate and selector switches. This will allow the ambidextrous select fire to continue to work. I didn’t make this modification on the A&K Masada conversion, but I think I could now go back and make it work, desired.
The PTS uses a custom selector plate, so the stock FE selector plate had to be abandoned and the PTS selector plate was modified to work with the FE. It worked out that the safety lever was still functional, but a wire add to be added to trigger the full-auto switch, and a couple of extra cuts were needed to accommodate the selector plate guide pin.
The nozzle on the PTS Masada is longer than the stock M4 nozzle (but actually shorter than the A&K Masada), so a custom nozzle had to be made using the same technique I’ve used on other custom installs (or a new nozzle could be made from an PolarStar SR25 nozzle blank).
The Magpul PTS Masada is an excellent gun. The externals are a little nicer than the A&K (I really like the retaining clips on the body pins), but the proprietary gearbox can be difficult to repair and upgrade. But with a PolarStar Fusion Engine, it becomes a low maintenance, top-of-the-line performance BB slinging machine. The Masada is my favorite AR platform, and now you can also take to dominating the field with a PolarStar Fusion Engine powered Magpul PTS Masada!