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

Version 2.1 of the hop-up alignment system, designed for M4 AEG HPA replicas with a V2 gearbox.

This kit is designed to combine the PolarStar JACK engine with the PolarStar HopUp chamber, maintaining a stable position between the nozzle and the chamber. The design uses a dedicated front cap to lock the chamber in the correct position.

This model is designed for the PolarStar JACK installed without direct attachment.

Compatibility

Component	Compatibility
HPA engine	PolarStar JACK
Engine configuration	Without direct attachment
Hop-up chamber	PolarStar HopUp
Base replica	M4 / AR15 AEG
Gearbox	V2

What's Included

• Rear clip for mounting via the rear pin or fixed stock.
• Base with mounting points for M3 inserts.
• Side clip to guide the HPA line.
• Dedicated upper front locking cap for the PolarStar HopUp chamber.
• Rear plate with an M5 screw mounting point.
• Guide components to reduce lateral movement of the assembly.

System Function

The Alignment Kit secures the relative position of the HPA engine and the hop-up chamber. This helps ensure that the PolarStar JACK nozzle enters the chamber centrally, promoting more consistent feeding and reducing potential misalignment during use.

The front cap locks the PolarStar HopUp chamber in place and prevents it from shifting forward, backward, or sideways. The side clip keeps the HPA line routed correctly, preventing kinks, rubbing, or unnecessary strain on the engine.

Installation and Adjustment

1. Printing and Preparation

   • Print the parts with an infill of 65% to 80%.
   • Lightly sand the internal and contact surfaces until a clean fit is achieved.
   • If necessary, apply dry lubricant or wax to the mounting surfaces.

2. Installation in the Replica

   • Insert the M3 inserts into the base.
   • Install the assembly in the lower receiver or V2 gearbox.
   • Install the PolarStar JACK in its standard mounting position, without a direct attachment system.
   • Install the PolarStar HopUp chamber together with the inner barrel.
   • Secure the front using the included cap and route the HPA line through the side clip.

3. Final Securing and Inspection

   • Secure the rear plate with an M5 screw and washer for additional rigidity.
   • Check that the nozzle enters the hop-up chamber centrally.
   • Perform dry feeding tests before pressurizing the system.
   • Adjust the hop-up and FCU settings according to BB weight, magazine, and power configuration.

Required Components (Not Included)

• 4× M3 × 4.2 mm inserts
• 4× M3 × 8 SHCS screws
• 1× M5 screw with washer for optional rear securing

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.