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PolarStar F2 M4 Conversion Kit | V2 HPA Unit | HPA Drop in Kit Reviews

4.9 Rating 20 Reviews
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This specific F2 is designed with the M4/M16 and typical Version 2 Gearboxes in mind.    
What is F2?
F2 is essentially a Mini Fusion Engine. It offers the same adjust-ability and performance as the Fusion Engine in a cylinder sized package.
Patented Dual Solenoid Design
The dual solenoid design of the F2™ provides the same functionality as the legendary Fusion Engine™ but in a more compact, efficient and flexible design. Dual solenoids allow for the nozzle and the poppet valve to be adjusted independently of each other for unparalleled control over both the loading time and air volume used. Additionally, this makes it possible to change the firing sequence giving it the ability to operate in both true closed bolt as well as "AEG" mode.
Increased Efficiency
The F2™ incorporates a new one-piece, lightweight poppet valve design yet still operates on the same principle as the Fusion Engine™ poppet. This valve is able to operate at lower pressures and uses less air volume to function which optimizes air efficiency.
The standard F2 poppet is equivilent to the Red Low-Flow poppet of the Fusion Engine.
The robust design of the F2™ allows for an operating pressure range of 45psi to 145psi which enables it to achieve velocities from CQB to DMR while employing only one nozzle for the entire velocity adjustment range. 
Spring Loaded NozzleThe F2™ nozzle is spring biased forward which provides a consistent loading force regardless of operating pressure. It shares the same spring as the Fusion Engine™ with both light and heavy spring options available to adjust the loading force. 
Complete Tuning Control
The F2™ comes complete with a Fire Control Unit (FCU) that has an LCD display that allows you to tune your F2 to your liking! Adjust it's dwell, rate of fire, burst modes, nozzle feeding, and more!
Specifications
Velocity Range: 250fps - 500fps
Operating Presure: 45-145 PSI
Compatibility: ALL AEG
Offset and Centerline cylinders and nozzles.
Wire harnesses are available in 7.5", 13" and 18" standard lengths
Interchangeable Bushing Inserts which prevent any movement of F2 within the gearbox.
Custom nozzle lengths available.
Low velocity poppets (< 1J) available.
Light and Heavy nozzle springs available.
What is the difference between F2, F1 and JACK?
Both F1 and JACK are "open bolt" systems, meaning the nozzle is in the rearward position when the system is idle and the round is fired during the forward movement of the nozzle. F2 is a dual-solenoid system which allows for complete control over the shot cycle.
What is the warranty for F2?
F2 systems are covered by a 1 year warranty against defects in material or manufacturing.
Compatability and Nozzles
Over 20 standard F2 nozzles are available for installation into a wide range of replicas. These are numbered, rather than named, since a single nozzle is often compatible with multiple replicas. The "Original Model" listed in the table is the replica from which the nozzle measurements were taken and is for reference.
If your gun is not listed in our Compatiblity Database a recommended nozzle length may calculated by measuring your original gearbox and applying the following formula: TIP = F + B - (A/2) - .057. A more precise measurement (which accounts for the hopup and bucking in use) may be obtained by installing a nozzle into the system which is slightly too long for the replica and measuring the nozzle setback when placed into the hopup.
If you do not see a Standard Nozzle listed within +/- .010" of the calculated measurement please contact us with your gearbox measurements and we can have PolarStar cut a custom nozzle for you.
Number - Original Model
1 - M4, VFC
2 - MP5-A4 TFB, ECHO 1 (CYMA)
3 - M249, CLASSIC ARMY
4 - SR-25, G&G
5 - SR-25, A&K
6 - M240B, ECHO 1
7 - MASADA, PTS
8 - SCAR-H, VFC
9 - TAVOR COMPETITION, EF (S&T)
10 - ARX160 ELITE, EF
11 - KAC LMG, CLASSIC ARMY
12 - AK, LCT
13 - MASADA, A&K
14 - Mk43 (M60), A&K
15 - G36KV, EF (ARES)
16 - G36C, EF (S&T)
17 - AUG, CLASSIC ARMY
18 - MP5, G&G, BLOWBACK
20 - G36K, CLASSIC ARMY
O-1 - M14, G&G
O-2 - P90, CLASSIC ARMY

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Probably the best HPA Engine money can buy
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Posted 2 months ago
Valid - thank you for the product review!
Posted 2 months ago
Great kit came with everything needed and was easy to install myself. I would definitely buy again.
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Posted 3 months ago
Bought this for a "featherweight" M249. Used to go "dak-dak-dak-dak-dak" Used Polarstar's install video. Including the foil tape. Now my featherweight goes "brrrrt."
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Posted 6 months ago
Kit is easy to drop in, really straight forward. My one gripe about the kit is that it doesn’t come with the air fitting for the grip line. I did not realize this when I ordered so I had to make a separate order for the airline. It really should just come with that so it’s ready to use out of the box. I put it in a featherweight m249.
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Posted 7 months ago
Thanks for the great review :) Yes - you are correct. The PolarStar kit does not come with the gun side fitting for the macro line. They never have.. not entirely sure why. We usually do include these for free if you get one of our Amped Player Packages. But the P* engine (and other companies engines) DO NOT come with the QD gunside fitting! So please be aware :)
Posted 7 months ago
This engine is absolutely amazing!!!
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Posted 1 year ago
Thank you very much for the review - arguably our favorite engine on the market as well!
Posted 1 year ago
KGROGACHEV​
Verified Reviewer
The best system I've ever played with.
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Posted 1 year ago
That's wonderful! Thank you for the review! :)
Posted 1 year ago
Easy to install and shoot great
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Posted 1 year ago
Thanks!
Posted 1 year ago
One of the best upgrades I have done. Pair it with a Maxx hop-up unit and you will be all set for an awesome experience.
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Posted 2 years ago
Spicy 🔥
Posted 2 years ago