PolarStar F1 + PolarStar HopUp · Alignment Kit V2.1 · M4 / AR15 AEG

Version 2.1 of the hop-up alignment system for M4 / AR15 AEG replicas with a V2 gearbox.

This model is designed to combine the PolarStar F1 engine with a PolarStar HopUp chamber in a standard configuration, without direct attachment. The upper cap keeps the chamber in position and helps maintain alignment between the nozzle and the chamber entrance during installation and operation.

The PolarStar F1 uses a dual-solenoid HPA system that allows independent adjustment of nozzle movement and air release. The PolarStar HopUp chamber for M4/V2 platforms uses a TDC adjustment system and is designed for both AEG and HPA configurations. [55][127]

Compatibility

Component	Compatibility
HPA engine	PolarStar F1 V1
Hop-up chamber	PolarStar HopUp
Base replica	M4 / AR15 AEG
Gearbox	Standard V2
Mounting system	Without direct attachment

What's Included

• Rear clip for mounting via the rear pin or fixed stock.
• Main base with M3 insert mounting points.
• Side clip to guide the PolarStar F1 HPA line.
• Upper cap for front locking and positioning of the PolarStar HopUp chamber.
• Rear plate with an M5 screw mounting point.
• Adjustment components to keep the assembly stable inside the V2 gearbox.

Installation and Adjustment

1. Preparing the Parts

   • Print the parts with an infill of 65% to 80%.
   • Lightly sand the internal surfaces and contact areas.
   • Use dry lubricant or wax on sliding surfaces if necessary.

2. Assembling the System

   • Insert the M3 inserts into the base.
   • Install the PolarStar F1 in the V2 gearbox, following the orientation specified in its conversion kit.
   • Install the PolarStar HopUp chamber with the inner barrel.
   • Fit the upper cap to lock the chamber in place and keep it centered.
   • Route the HPA line through the side clip to prevent rubbing and sharp bends.

3. Securing and Checking

   • Secure the rear plate with an M5 screw and washer.
   • Check that the nozzle enters the chamber centrally, without lateral pressure.
   • Perform dry feeding tests before using BBs.
   • Adjust the hop-up and F1 programming according to your barrel, bucking, and BB weight configuration.

Required Components (Not Included)

• 4× M3 × 4.2 mm inserts
• 4× M3 × 8 SHCS screws
• 1× M5 screw with washer
• Complete HPA system: air tank, regulator, HPA line, and battery compatible with the F1 FCU.

Recommended Lower Receivers

A metal ICS lower receiver is recommended when maximum rigidity is required.

If you prefer to print your own lower receiver, the following Gearbox V2 Lower — Universal Lower models are compatible:

• Version 3
• Version 4.2
• Version 4.3 MTW

You can find them HERE.

3D Printing Parameters

• Approximate print time: ~1 h 30 min
• Recommended material: PLA+
• Layer height: 0.10 mm – 0.15 mm
• Recommended infill: 65% – 80%

Manuals

Installation and adjustment manuals are available in the Manuals section of the website or on the project's Discord server.