Back
Sin título
Sin título

PolarStar JACK + RetroArms alignment kit for M4 AEG (v2.1)

23,00 €
1
Share on social media:

Version 2.1 of the hop-up alignment system, designed for M4 / AR15 AEG HPA replicas using:

  • PolarStar JACK engine (drop-in HPA kit, compatible with a wide range of V2 gearboxes with a centerline nozzle).
  • RetroArms hop-up chamber for M4/AR15 (high-precision CNC chamber, designed for a solid, stable, and reliable fit in HPA builds).

This kit ensures precise alignment between the JACK nozzle and the RetroArms chamber, reducing play, improving feeding, and providing a more consistent base for HPA setups with V2 split / ICS gearboxes.

Compatibility

Component Compatibility
HPA Engine PolarStar JACK
Hop-up Chamber RetroArms M4 / AR15
Base Replica M4 / AR15 AEG
Gearbox V2 / ICS SPLIT

What’s included in the kit

  • Rear clip for mounting via rear pin or fixed stock
  • Base with housing for M3 inserts (brass optional)
  • Side clip for routing the JACK HPA line
  • Top locking cap for the RetroArms chamber
  • Rear plate with mounting point for an M5 screw (extra reinforcement)

Installation and setup

  1. Printing and preparation

    • Print parts with 65–80% infill
    • Lightly sand internal/contact areas for a clean fit
    • If needed, apply dry lubricant or wax on sliding surfaces

  2. Assembly on the replica

    • Insert the base into the lower and install the M3 inserts
    • Place the rear clip aligned with the rear pin or stock mounting point
    • Install the RetroArms chamber with the inner barrel; the top cap locks the assembly and keeps the barrel centered
    • Route the JACK HPA line through the side clip to prevent rubbing or kinks

  3. Final fixing

    • Secure the rear plate with an M5 screw and washer for maximum rigidity
    • Check that the JACK nozzle enters the RetroArms chamber centered and that feeding is consistent
    • Perform dry tests and adjust hop-up according to BB weight and bucking

Required components (not included)

  • 4× M3 × 4.2 mm inserts
  • 4× M3 × 8 SHCS screws

Lower receiver recommendations

Using a metal ICS lower is recommended for maximum rigidity.
If you prefer to print your own lower, these Gearbox v2 Lower "Universal lower part" models are compatible:

  • Version 3
  • Version 4.2
  • Version 4.3 MTW

You can find them HERE.

3D printing parameters

  • Estimated print time: ~1 h 30 min
  • Recommended material: PLA+
  • Layer height: 0.10 mm – 0.15 mm

Manuals

Installation and setup manuals are available in the Manuals section on the website or on the project’s Discord server.

Related products and articles

Similar product designs:

Technical articles for this topic:

Frequently asked questions

What material and dimensions apply to PolarStar JACK + RetroArms alignment kit for M4 AEG (v2.1)?

The public product data does not declare a material or finished dimensions for this design. Check the images, downloadable files, and the exact manufacturing or printing setup before producing it.

What is PolarStar JACK + RetroArms alignment kit for M4 AEG (v2.1) compatible with?

The published tags and categories identify this design with m4, ar15, polarstar jack, retroarms, hpa, airsoft. Confirm the exact platform, revision, and mounting points before ordering.

How do I install or prepare PolarStar JACK + RetroArms alignment kit for M4 AEG (v2.1)?

Read the installation notes in the product description, inspect the supplied files and images, and test alignment before final fastening. The required tools, fasteners, printing parameters, or post-processing depend on the specific build.

What are the real-world uses for PolarStar JACK + RetroArms alignment kit for M4 AEG (v2.1)?

This design is intended for projects related to m4, ar15, polarstar jack, retroarms, hpa, airsoft. It is useful for a compatible repair, conversion, prototype, replacement, or custom build when the published fitment and project requirements match.