RedLine N7 Gen 1 + 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.

This kit is designed to combine the RedLine N7 Gen 1 engine with the PolarStar HopUp chamber, maintaining a stable position between the nozzle and the chamber entrance. The result is more consistent feeding, reduced lateral play, and a more rigid assembly for HPA configurations based on the M4 platform.

Compatibility

Component	Compatibility
HPA engine	RedLine N7 Gen 1
Hop-up chamber	PolarStar HopUp
Base replica	M4 / AR15 AEG
Gearbox	V2
System	HPA

What's Included

• Rear clip for mounting via the rear pin or fixed stock.
• Alignment base with mounting points for M3 inserts.
• Side clip to guide the HPA line and prevent rubbing or kinks.
• Upper front locking cap to keep the PolarStar HopUp chamber in position.
• Rear plate with an M5 screw mounting point, designed to reinforce the assembly.

System Function

The kit keeps the hop-up chamber in a controlled position relative to the HPA engine. This helps ensure that the RedLine N7 Gen 1 nozzle enters the PolarStar HopUp chamber centrally, reducing feeding inconsistencies caused by chamber movement or tolerances between components.

The structure also guides the HPA line and allows the assembly to be secured more firmly inside the V2 gearbox.

Installation and Adjustment

1. Printing and Preparation

   • Print the parts with an infill of 65–80%.
   • Lightly sand the internal and contact surfaces to achieve a clean fit.
   • Apply dry lubricant or wax to sliding surfaces if necessary.

2. Base Installation

   • Install the M3 inserts in the designated mounting points.
   • Position the base in the lower receiver or gearbox according to the replica configuration.
   • Install the rear clip using the rear pin or stock mounting point.

3. Chamber and Engine Installation

   • Install the PolarStar HopUp chamber together with the inner barrel.
   • Fit the upper cap to lock the chamber in the correct position.
   • Install the RedLine N7 Gen 1 engine and route the HPA line through the side clip.

4. Final Securing

   • Use an M5 screw with washer on the rear plate to provide additional rigidity.
   • Check that the nozzle enters the chamber centrally without rubbing against its walls.
   • Perform dry feeding tests before using BBs, and adjust the hop-up according to the BB weight being used.

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 to achieve maximum rigidity in demanding 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.