PolarStar F2™ HPA Conversion Kit Classic Army KAC LMG

PolarStar F2™ Classic Army KAC LMG dual-solenoid HPA system

This expert product description was prepared by the ANAREUS.cz expert team. All rights to this unique content are bound to the anareus.cz domain.PolarStar F2™ is a compact HPA conversion system for M249 and MK46 AEG machine guns with a "brick" type gearbox (M249), based on the design of the legendary PolarStar Fusion Engine™. Its key advantage is its dual-solenoid design. The nozzle and poppet valve are controlled separately, allowing the BB feeding process and the amount of air used for each shot to be controlled independently. This independent control of both solenoids gives the F2™ a very wide range of adjustment options. The system allows you to adjust nozzle dwell and poppet dwell, RoF and burst mode, and supports operation in both true closed bolt and AEG modes. Settings are controlled by the included FCU (Fire Control Unit). According to the manufacturer, the default FCU settings are suitable for most standard installations, while advanced tuning allows the system to be adapted to a specific gun, magazines and desired behaviour. A 7.4V HPA battery with a JST connector is required to power the electronics and is not included. The F2™ uses a one-piece lightweight poppet valve that operates on the same principle as the Fusion Engine™ valve but requires lower pressure and less air volume to function. The result is high system efficiency and the ability to operate across a wide input pressure range of 45 to 145 PSI. Power is adjusted primarily by changing the input pressure from the regulator, so there is no need to change the nozzle across the entire power range. With its reference VFC M4 setup using a 6.05 × 380 mm barrel, PolarStar states approximately 60–150 m/s with 0.20g BBs within the 45–145 PSI range. Actual performance can vary significantly depending on barrel length and diameter, air seal, hop-up assembly and the overall configuration of the specific gun. The F2™ nozzle is spring-loaded forward, so its feeding force is not dependent on the selected operating pressure. The system uses the same type of nozzle spring as the Fusion Engine™ and allows lighter or stronger springs to be used for further adjustment of the feeding force. The PolarStar F2™ interchangeable nozzle system also allows it to be used in other guns with a compatible gearbox.

Key features of the PolarStar F2™

Technical specifications

• Manufacturer: PolarStar
• Model: F2™
• Type: HPA conversion system
• Design: Dual solenoid
• Control: FCU (Fire Control Unit)
• System mode: True Closed Bolt / AEG mode
• Operating pressure: 45–145 PSI
• Power adjustment: By changing the input pressure
• Manufacturer's reference performance: Approx. 250–480 FPS with 0.20g BBs at 45–145 PSI*
• Maximum RoF: Approx. 30 RPS*
• Reference efficiency: 1000+ shots from a 13/3000 tank at 1.5 J with 0.28g BBs*
• Nozzle: Spring-loaded forward
• Compatibility of this version: Classic Army KAC Stoner LMG AEG gearbox
• Material: Aluminium alloy
• Colour: Red

* The stated values represent the manufacturer's reference results and are not guaranteed performance figures for every setup. PolarStar uses a standard VFC M4 with an approximately 6.05 × 380 mm barrel for performance measurements. The resulting muzzle velocity, RoF and air consumption depend on the gun configuration, barrel length, operating pressure, magazine used, BBs and system settings.

Package contents

• 1× PolarStar F2™ HPA Engine Classic Army KAC LMG
• 1× FCU (Fire Control Unit)
• 1× Switchboard for the respective kit version
• 1× Wire Harness
• 1× PolarStar Filter Fitting

HPA tank, regulator, air line and battery are not included and must be purchased separately.

Warnings and installation

• PolarStar F2™ is an advanced HPA conversion system designed for installation into the shell of the original AEG gearbox.
• For correct installation, checking the alignment of the nozzle and hop-up unit, and subsequent adjustment, we recommend having appropriate experience with HPA systems or entrusting the installation to an experienced HPA gun service technician.
• During installation, it is important to connect both solenoids to the switchboard correctly.
• On the M249 version, the ports are marked P = Poppet and N = Nozzle. Swapping them can cause BB feeding problems.
• It is also necessary to check the free movement of the selector plate around the microswitch, the routing of the wiring and sufficient clearance between the spring guide and the end sections of the solenoids.
• A 7.4V HPA battery with a JST connector is required to power the electronics and is not included. Alternatively, a 3.7V battery can also be used.
• Operation also requires a suitable HPA setup including a pressure tank, regulator, air line and appropriate fittings.
• Also read our guide on how to assemble an HPA setup.

Frequently asked questions from our store

What is the main difference between the PolarStar F2™ and a simpler single-solenoid HPA system?

The F2™ uses two independently controlled solenoids. One controls the movement of the nozzle and the other controls the poppet valve, allowing BB feeding and the amount of air used for each shot to be adjusted independently. This provides significantly wider options for tuning the system timing.

How is the power of the PolarStar F2™ adjusted?

Muzzle velocity is adjusted primarily by changing the input pressure on the regulator. The recommended operating range of the F2™ is 45–145 PSI. Actual performance at a specific pressure depends primarily on the barrel length and configuration and other parameters of the gun.

Is it necessary to change the nozzle when adjusting power?

Not for normal power adjustment within the system's range. One of the advantages of the F2™ is its ability to cover a wide muzzle velocity range using a single nozzle and changes in input pressure. Interchangeable nozzles are primarily used to adapt the system to different types of guns.

What else is required to operate the PolarStar F2™?

In addition to the kit itself, you primarily need an HPA tank, regulator, air line and a battery to power the electronics. According to the manufacturer, these components are not included with the kit.