GATE Pulsar-S + PolarStar HopUp · Alignment Kit V2.1 · M4 AEG HPA

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

• GATE Pulsar-S HPA engine.
• PolarStar HopUp chamber.

This kit maintains stable positioning between the GATE Pulsar-S nozzle and the PolarStar HopUp chamber. Its goal is to reduce lateral chamber play, improve nozzle entry, and achieve more consistent feeding during use.

The structure is designed for M4 AEG builds with a V2 gearbox. The system provides additional chamber support points, HPA line routing, and rear fastening, creating a more rigid assembly that is easier to maintain.

Compatibility

Component	Compatibility
HPA Engine	GATE Pulsar-S
Hop-up Chamber	PolarStar HopUp
Base Replica	M4 AEG / AR15 AEG
Gearbox	V2
System	HPA

What's Included in the Kit

• Rear clip for mounting via the rear pin or fixed stock.
• Alignment base with mounting points for M3 inserts.
• Side clip for routing the HPA line.
• Upper front locking cap for the PolarStar HopUp chamber.
• Rear plate with a mounting point for an M5 screw.
• Support points designed to keep the chamber centered relative to the HPA engine.

Installation and Adjustment

1. Printing and Preparation

   • Print the parts with 65–80% infill.
   • PLA+ is recommended for good rigidity and dimensional stability.
   • Lightly sand the internal and contact surfaces to achieve a clean fit.
   • Apply dry lubricant or wax to sliding surfaces if you want to facilitate maintenance.

2. Assembly

   • Insert the 4× M3 × 4.2 mm inserts into the base.
   • Secure the base using 4× M3 × 8 SHCS screws.
   • Position the GATE Pulsar-S inside the V2 gearbox.
   • Install the PolarStar HopUp chamber with the inner barrel.
   • Fit the upper cap to lock the chamber in the correct position.
   • Route the Pulsar-S HPA line through the side clip.

3. Final Securing

   • Install the rear clip using the replica's rear pin or fixed stock mounting system.
   • Secure the rear plate with an M5 screw and washer to increase the assembly's rigidity.
   • Check that the nozzle enters the chamber centrally, without friction or excessive lateral pressure.
   • Perform dry feeding tests before using BBs.

Required Components

• 4× M3 × 4.2 mm inserts
• 4× M3 × 8 SHCS screws
• 1× M5 screw
• 1× M5 washer

Lower Receiver Recommendations

For maximum rigidity, a metal ICS lower receiver is recommended.

You can also use a 3D-printable lower receiver compatible with V2 gearboxes:

• Gearbox V2 Lower — Universal Lower Version 3
• Gearbox V2 Lower — Universal Lower Version 4.2
• Gearbox V2 Lower — Universal Lower Version 4.3 MTW

You can find them HERE.

3D Printing Settings

• Approximate Printing Time: ~1 hour 30 minutes
• Recommended Material: PLA+
• Recommended Layer Height: 0.10 mm–0.15 mm
• Recommended Infill: 65–80%
• Supports: Not required unless necessary for your chosen print orientation

Manuals

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