GATE Pulsar D1 + 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 D1 HPA engine.
• PolarStar HopUp chamber.

This kit maintains a stable position between the Pulsar D1 nozzle and the PolarStar HopUp chamber. Its purpose is to reduce play, improve feeding consistency, and keep the barrel and hop-up chamber assembly properly centered in an M4 platform with a V2 gearbox.

Compatibility

Component	Compatibility
HPA engine	GATE Pulsar D1
Hop-up chamber	PolarStar HopUp
Base replica	M4 AEG / AR15 AEG
Gearbox	V2
System	HPA

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.
• Upper front locking cap for the PolarStar HopUp chamber.
• Rear plate with an M5 screw mounting point.
• Support components to keep the chamber and engine aligned during installation.

Installation and Adjustment

1. Preparing the Parts

   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 sliding surfaces.

2. Assembly

   Insert the base into the lower receiver and install the M3 inserts. Position the GATE Pulsar D1 in the V2 gearbox and route its HPA line through the side clip. Install the PolarStar HopUp chamber alongside the inner barrel and secure the assembly with the upper cap.

3. Final Securing

   Align the rear clip with the replica's rear pin or stock mounting point. Use an M5 screw with washer on the rear plate to increase rigidity. Before closing the replica, check that the nozzle enters the chamber straight and centrally, without lateral rubbing.

Recommendation: Perform dry feeding tests before using BBs. Then adjust the hop-up and engine settings according to BB weight and the power limits permitted at your field.

Required Components (Not Included)

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

Recommended Lower Receivers

A metal ICS lower receiver is recommended to achieve maximum rigidity in HPA configurations.

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.