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

Version 2.1 of the alignment system for M4 AEG HPA replicas with a V2 gearbox, designed to combine the PolarStar JACK engine with the Direct Attachment system and the PolarStar V2 HopUp Thing chamber.

The Direct Attachment system replaces the JACK's original front cylinder and connects the engine directly to the PolarStar chamber. This allows the HPA engine, hop-up, and inner barrel to form a single rigid assembly, reducing movement between components and helping maintain more consistent feeding.

Compatibility

Component	Compatibility
HPA Engine	PolarStar JACK
Adapter	PolarStar Direct Attachment for JACK
Hop-up Chamber	PolarStar V2 HopUp Thing
Base Replica	M4 / AR15 AEG
Gearbox	V2
Mounting System	Direct Attachment

This kit is designed for use with the PolarStar V2 HopUp Thing chamber. The Direct Attachment threads directly into this chamber, making it incompatible with other hop-up chambers.

What's Included in the Kit

• Alignment lower for M4 / AR15 platforms with a V2 gearbox.
• Mounting base for the PolarStar JACK + Direct Attachment assembly.
• Rear support for mounting via the rear pin or fixed stock.
• Side guide for the HPA line.
• Mounting points for M3 inserts.
• Rear reinforcement support for an M5 screw.
• Dedicated spaces for mounting and routing electronic components.

How the System Works

The Direct Attachment connects the PolarStar JACK directly to the PolarStar HopUp Thing. This connection eliminates independent movement between the engine and the hop-up chamber.

The kit is designed to maintain:

• The nozzle centered relative to the chamber entrance.
• A stable chamber during assembly and use of the replica.
• Proper guidance of the inner barrel.
• Consistent feeding alignment relative to the magazine.
• Clean routing of the HPA line and FCU wiring.

Installation and Adjustment

1. Preparing the Parts

   • Print the parts with 65%–80% infill.
   • Lightly sand the contact surfaces to achieve a clean fit.
   • Use dry lubricant or wax on sliding surfaces if necessary.

2. Installing the Direct Attachment

   • Remove the original front cylinder from the PolarStar JACK.
   • Install the Direct Attachment front cylinder and its internal adapter.
   • Remove the front lip of the PolarStar HopUp Thing gearbox.
   • Thread the PolarStar chamber onto the adapter until the feed tube is correctly oriented.

3. Installing the Assembly in the Lower Receiver

   • Position the JACK + Direct Attachment + HopUp Thing assembly in the lower receiver.
   • Insert the M3 inserts into their designated mounting points.
   • Install the rear clip and align it with the replica's rear pin.
   • Route the HPA line through the side support to prevent kinks or friction.

4. Final Adjustment

   • Secure the rear reinforcement with an M5 screw and washer.
   • Check that the magazine inserts freely and feeds correctly.
   • Verify that the nozzle enters the chamber centrally without lateral tension.
   • Perform feeding tests before fully closing the replica.

Required Components

• PolarStar JACK HPA Engine.
• PolarStar Direct Attachment for JACK kit.
• PolarStar V2 HopUp Thing chamber.
• Compatible inner barrel, bucking, and nub.
• 4× M3 × 4.2 mm inserts.
• 4× M3 × 8 SHCS screws.
• M5 screw and washer for rear reinforcement.
• HPA line, regulator, air tank, and FCU compatible with the PolarStar JACK.

3D Printing Recommendations

• Recommended Material: PLA+.
• Layer Height: 0.10 mm–0.15 mm.
• Recommended Infill: 65%–80%.
• Approximate Printing Time: ~1 hour 30 minutes.
• Check and clean the mounting holes before inserting the hardware.
• Do not force the parts together. Use fine sanding to adjust any areas that fit too tightly.

Important Notes

• This design is intended for V2 gearboxes in M4 / AR15 AEG platforms.
• The Direct Attachment assembly combines the engine, chamber, and inner barrel into a rigid structure.
• The final chamber orientation must allow proper magazine insertion and reliable feeding.
• Before making permanent modifications, test-fit all components in the replica and confirm the position of the feed tube.
• The replica must always comply with local regulations regarding power, energy limits, and airsoft use.

Manuals

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