Redline N7 Gen 2 + PolarStar HopUp · Alignment Kit V2.1 · M4 AEG HPA

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

This kit is designed to combine the Redline N7 Gen 2 engine with a PolarStar HopUp chamber, maintaining stable positioning between the nozzle and the chamber entrance. The goal is to reduce lateral movement, improve feeding consistency, and make hop-up adjustments more repeatable.

The Redline N7 Gen 2 features a closed-bolt design with an extended nozzle. For this reason, proper alignment between the engine, chamber, and inner barrel is especially important for reliable feeding and a stable HPA setup.

Compatibility

Component	Compatibility
HPA Engine	Redline N7 Gen 2
Hop-up Chamber	PolarStar HopUp
Base Replica	M4 / AR15 AEG
Gearbox	V2
Recommended Lower Receiver	Metal ICS / Compatible universal lower

What's Included in the Kit

• Alignment base for the Redline N7 Gen 2 engine.
• Rear clip for mounting via the rear pin or fixed stock.
• Upper front locking cap for the PolarStar HopUp chamber.
• Side clip for routing the HPA line.
• Rear plate with a mounting point for an M5 screw.
• Mounting points for M3 inserts.

Installation and Adjustment

1. Preparing the Parts

   • Print the parts with 65%–80% infill.
   • Lightly sand the internal and contact surfaces.
   • Apply dry lubricant or wax if you want to facilitate assembly and future maintenance.

2. Assembly

   • Install the M3 inserts in the base.
   • Position the Redline N7 Gen 2 inside the V2 gearbox.
   • Install the PolarStar HopUp chamber with the inner barrel.
   • Fit the upper cap to lock the chamber in place and keep the assembly centered.
   • Route the HPA line through the side clip to prevent friction, twisting, or excessively tight bends.

3. Final Securing

   • Align the rear clip with the replica's rear pin or stock mounting point.
   • Secure the rear plate with an M5 screw and washer to increase rigidity.
   • Check that the nozzle enters the chamber centrally without lateral pressure.
   • Perform dry feeding tests before adjusting the hop-up and operating pressure.

Important: Check nozzle alignment before firing. An incorrectly positioned chamber can cause inconsistent feeding, bucking wear, or reduced consistency.

Required Components (Not Included)

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

Lower Receiver Recommendations

A metal ICS lower receiver is recommended for 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 Settings

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

Manuals

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