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PolarStar Kythera SA V2.5 + Silent Industries ALPHA 2026 · Alignment Kit · SR25 AEG HPA

23,00 €
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Alignment kit designed for SR25 AEG HPA replicas with a V2.5 gearbox and PolarStar Kythera SA V2.5 mechanical engine.

The system uses the Silent Industries ALPHA 2026 hop-up chamber, keeping the Kythera nozzle perfectly centered relative to the chamber. This helps improve feeding consistency, reduce lateral movement, and make more efficient use of the HPA system's pressure.

The PolarStar Kythera is a mechanical HPA engine designed for semi-automatic operation. It does not require a battery, FCU, or electronic components to operate. This version is designed for V2.5 or extended V2 gearboxes used in certain SR25 replicas.

Important: This kit is designed for the Silent Industries ALPHA 2026 chamber. The external geometry of this revision may differ from previous versions of the ALPHA chamber. Compatibility between revisions should not be assumed without checking the dimensions first.

Compatibility

Component Compatibility
HPA Engine PolarStar Kythera SA V2.5
Hop-up Chamber Silent Industries ALPHA 2026
Base Replica SR25 AEG
Gearbox V2.5 / Extended V2
Operation Mechanical HPA, semi-automatic

What the Kit Includes

  • Rear clip for mounting using the rear pin or fixed stock.
  • Alignment base for V2.5 gearbox.
  • Housing for M3 inserts.
  • Side clip for guiding the HPA tube or line.
  • Upper front locking cap for the Silent Industries ALPHA 2026 chamber.
  • Rear plate with mounting point for an M5 screw.
  • Support elements to keep the nozzle, chamber, and inner barrel centered.

Installation and Adjustment

1. Printing and Preparation

  • Print the parts with an infill between 65% and 80%.
  • Lightly sand the internal areas and contact surfaces.
  • Make sure the parts fit without forcing the gearbox or hop-up chamber.
  • If necessary, use dry lubricant or wax on sliding surfaces.
  • Do not remove material from the alignment areas until the complete assembly has been checked.

2. Installation on the Replica

  • Install the kit base onto the lower or structure compatible with the V2.5 gearbox.
  • Install the M3 inserts into their housings.
  • Position the rear clip aligned with the rear pin or stock mounting point.
  • Install the PolarStar Kythera SA V2.5 into the SR25 gearbox.
  • Install the Silent Industries ALPHA 2026 chamber together with the inner barrel.
  • Make sure the Kythera nozzle enters the chamber without rubbing or lateral movement.
  • Route the HPA line through the side clip to prevent rubbing and excessively tight bends.

3. Final Securing

  • Install the upper cap to lock the front position of the chamber.
  • Secure the rear plate using an M5 screw and washer.
  • Make sure the assembly has no play before closing the replica.
  • Perform feeding tests with the magazine installed.
  • Adjust the Kythera pressure and hop-up progressively according to the SR25 configuration.

Required Components (Not Included)

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

The M3 hardware is used to secure the kit base. The M5 screw provides additional support at the rear and improves the rigidity of the assembly.

Lower Recommendations

A metal lower compatible with SR25 and V2.5 gearboxes is recommended for maximum rigidity.

If you prefer to print the lower section, you can find the Gearbox v2 Lower "Universal Lower" models available in the universal lower section:

  • Version 3
  • Version 4.2
  • Version 4.3 MTW

You can find them HERE.

Note: Universal lowers versions 3, 4.2, and 4.3 are primarily designed for V2, ICS, and related configurations. On an SR25 replica with a V2.5 gearbox, it may be necessary to check the dimensions, magazine well, nozzle position, and compatibility with the external body before printing.

Gearbox Compatibility and Limitations

SR25 V2.5 gearboxes typically use an extended geometry compared to a standard V2 gearbox. The external shape and nozzle position may vary depending on the replica manufacturer.

Before installation, check:

  • V2.5 gearbox length and position.
  • Nozzle type used by the PolarStar Kythera.
  • Distance between the nozzle and the ALPHA 2026 chamber.
  • Magazine position relative to the chamber.
  • Lower and external body compatibility.
  • Trigger travel and safety system operation.

3D Printing Parameters

  • Approximate printing time: ~1 h 30 min.
  • Recommended material: PLA+.
  • Layer height: 0.10 mm – 0.15 mm.
  • Recommended infill: 65% – 80%.
  • Supports: use only where necessary depending on the orientation of each part.

Manuals

Installation and adjustment manuals are available in the Manuals