Wednesday, October 5, 2022
Home » Reviews » PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition

PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition

The introduction of the PolarStar Fusion Engine within the last two years has sent the airsoft industry in a new direction, whether it likes it or not. Some players were very welcoming, others unsure but intrigued, and then some were against it, claiming it’s a step back towards paintball. Add to that the complaints that roll in from anyone who’s been steamrolled by someone else running a PolarStar system on full-auto, generally running at rates of fire around 30 RPS or higher, and you’ve got yourself a bunch of “P* haters.” That’s cool. I can understand your point of view if that’s you. It’s not for everyone, though. I, for one, have always been impressed by the engineering and ingenuity it took to create this thing from scratch and just how well the finished product turned out. Factor in the performance and reliability and you’ve got yourself a pretty incredible system to take out on the field.

WHO MAKES IT: PolarStar Airsoft
MODEL: Fusion Engine, GEN3 for Version 2 AEG
CLASS: HPA-powered, with some electricity mixed in. It’s a “fusion.”
TYPE: Drop-in, solenoid-driven gearbox replacement
WHO IT’S FOR: Advanced players
HOW MUCH: $500 for the Fusion Engine Drop-In Kit; $670 for a fully assembled PolarStar EPAR PR-15. Does not include cost of the air system.
FPS: Fully Adjustable, based on the nozzle installed and regulator pressure (80 psi to 120 psi).
ROF: Adjustable from500 RPM (8 RPS) to 1,800 RPM (30 RPS); user-controlled using the on-board Fire Control Unit (FCU).
FIRE MODES: Semi-Auto, Full-Auto and Variable Burst (two-shot through nine-shot burst)
PLATFORMS: Version 2 rifles (M4/M16, MP5, G3, SCAR), Version 3 rifles (AK series), Echo1 M240 Bravo, and M249 SAW. Custom retrofitting is available for other platforms as well.

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition
Made of high-grade aluminum, the PolarStar Fusion Engine is a drop-in gearbox replacement for Airsoft AEG rifle bodies. The engine itself is powered by a small battery whose voltage can range from 6.8V to 12V according to the user’s preference, and it uses the power of solenoid-driven high-pressure air (HPA) supplied from an external, paintball-style air tank.

+ Designed, manufactured and built in the United States
+ Assembled from CNC-machined aluminum components
+ GEN3 design now interfaces with AEG triggers and selector plates for cross compatibility with many different models
+ Capable of functioning in damp and sub-freezing climates without affecting performance or reliability
+ User selectable Semi/Full-Auto, Semi-Auto Only and Variable Burst modes
+ Open Bolt and Closed Bolt firing modes
+ Independently adjustable velocity and cyclic rate
+ Auto Switch mode allows for proper selector configuration for specific models
+ Interchangeable air nozzles to shift the velocity adjustment range up or down
+ Adjustable nozzle dwell and return to battery times to optimize feeding from any magazine
+ Easy to use Fire Control Unit (FCU) with LCD display and five position joystick
+ Uniform shot-to-shot air volume discharge allows for unmatched velocity consistency
+ Instantaneous trigger response. Faster than an AEG with a LiPo!
+ Interfaces with stock AEG barrel/hop-chamber, allowing for aftermarket barrel upgrades and the use of traditional AEG magazines
+ Can be purchased as a drop-in kit for an existing AEG body you already own, or as a fully assembled PR-15 rifle (pictured)

– High cost of required system components can be prohibitive for many players (air system sold separately)
– External air tank with remote air line can be cumbersome to some (author barely noticed this while playing, though)
– Some fields may not allow them due to lack of understanding of how they work or how to regulate the players using them (Google “paintball tournament lock” for cryin’ out loud, people!)
– Some people can’t handle how awesome these things are and just hate on them because they can
– Some would argue that PolarStar guns aren’t “MilSim” enough

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition

Complete Tokyo Marui spec AEG rifle (less gearbox and motor), remote air line and regulator, HPA tank and battery

Wow. Performance is pretty much what you’d expect from a U.S.-based precision engineering company who earns at least part of its revenues through the manufacturing of high performance automotive racing parts: outstanding and something that really can’t be matched by a standard AEG or even a Systema PTW (Gasp! How dare you utter such blasphemy?) I know, I know.

No disrespect to the PTW; those things are sweet, but even they can’t compete in the reliability arena. If I remember correctly, PolarStar released a rough video clip during their R&D phase where they were stress-testing their system and rigged up a machine that would automatically pull the trigger on the fusion engine so they could test the number of trigger pulls the engine could handle before failing. As I recall, they exceeded over one million trigger pulls. There is virtually no wear and tear on these engines thanks to the simple mechanics of their solenoid-driven internals, although a small amount of cleaning maintenance is recommended to prevent issues. There are only two or three moving parts at most, I believe.

From average to insanity with the toggle of the FCU joystick. That’s right. The rate of fire (ROF) is adjustable using the on-board Fire Control Unit, rated from about eight rounds per second up to about 30 rounds per second. Although I know it can go higher, you start to run into the limitations of your magazine follower springs and their ability to feed BBs quick enough. What a great problem to have!

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition
The FCU located in the stock tube.

One of the controversial aspects of the PolarStar Fusion Engines is their use of an external air rig, which allows the user to adjust velocities on the fly (unless you’ve got a tournament lock installed for a specific game). In addition to being able to adjust velocity using the air rig’s regulator, the Fusion Engine utilizes an interchangeable air nozzle that can be swapped out with several other air nozzles (all made by PolarStar), which allows the user to shift the velocity range of the rifle up or down as desired, usually in about 50 FPS intervals. Each nozzle is designated by color. For instance, the standard nozzle that comes with the system is the blue version, which gives the user an adjustable velocity range from about 350 FPS to 400 FPS with a .20g BB. PolarStar recommends the use of Elite Force BBs with their systems. Shot-to-shot velocity consistency is extremely high. We’re talking about a one to two FPS variance in either direction, all day, in just about any weather condition. PolarStar’s “A-Game” is truly on another level.

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition

One of my favorite features of the PolarStar Fusion Engine and one that never ceases to impress me is the adjustable burst-fire mode, which, again, is toggled on the FCU. When the rifle’s selector switch is set to fire full-auto, the FCU will allow you to toggle burst-fire mode instead of firing on continuous full-auto. You can set it to fire anywhere from a two-round burst (double-tap!) to a nine-round burst. I played around with this for a while in my garage one night, just trying to see if the system would ever skip a shot anywhere along the line of bursts, but it never missed a beat (or shot, in this case).

Lightning quick. While the fusion engine uses a standard AEG trigger and safety lever assembly, it utilizes a small button switch rather than the traditional AEG trigger assembly. The button is very small and requires very little length of pull from the trigger to be activated; so much of the trigger pull distance is really just excess. Because of this, I prefer to insert a small spacer on my trigger assembly to shorten the distance I need to pull in order to activate the button and fire the weapon. The safety lever inside the trigger assembly will need to be permanently shortened to function properly, so be sure you know what you’re doing before you attempt this mod. However, I can tell you that if done effectively, the result is an incredibly short length of pull and extremely fast trigger response.

PolarStar Fusion Engines were designed to interface with standard AEG hop-up assemblies and inner barrels, so the accuracy of the rifle is going to be dependent on how well you have your hop-up set up. Assuming you’ve got it set right, you’re going to have a good time.

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition
Seen above are the flip-up sights.

Due the nature of these systems, the muzzle report is affected by the flash hider, compensator or mock suppressor you have on the end of your rifle. These systems are fairly loud in their natural form; however, some mock suppressors will actually reduce the audible signature of the rifle, making it quieter. Conversely, I’ve been told by those with experience that using something like the MadBull Noveske sound-amplifying compensators will increase the sound report if you want to make your presence very well known on the field.

Review: PolarStar Fusion Engine, for Version 2 AEG Rifles, GEN3 Edition
A look at the PR 15 receiver.

This really is an incredible system, from the high-quality parts and materials used to create it to the intelligent design of its numerous features and performance characteristics. While I will concede that the realism factor many players value had to be sacrificed, there are a number of gains over the traditional AEG platform which I find attractive: primarily, the lack of maintenance or need to repair. I truly despise having to take apart a gearbox these days. I’ve lost the patience for it. If you’re the type of player who likes to take the game seriously, and just wants to go out and play it without having to worry about whether your gun is going to function that day, then the PolarStar Fusion Engine is certainly worth considering. In all honesty, I really didn’t find the remote line annoying, cumbersome or otherwise inhibitive of my movement or operation of the rifle, nor did it have any effect on my enjoyment of using the system during games. The air tank does add a little bit of weight to your kit, but not enough for someone as out-of-shape as I am to notice, so I doubt you crazy Crossfit guys would even think twice about it.

I’m giving this a five-star rating because the performance, quality and fun-factor are all off the charts by traditional airsoft standards.

PolarStar,, 302-449-4866

Words: Tom Harris
Photos: Walter Sidas & Tom Harris