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Kit de alineacion par SR25 - Polarstar F2 & Alpha
Kit de alineacion par SR25 - Polarstar F2 & Alpha

PolarStar F2 + Silent Industries ALPHA · Alignment Kit V2.1 · SR25 AEG HPA

23,00 €
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Version 2.1 of the hop-up alignment system, designed for SR25 AEG HPA replicas with a V2.5 gearbox.

This kit is designed to use the SR25-specific PolarStar F2 engine together with the Silent Industries ALPHA hop-up chamber. Its purpose is to keep the nozzle properly centered relative to the chamber, reducing lateral movement and improving feeding consistency in DMR-style HPA configurations.

The V2.5 gearbox is an extended version of the V2, commonly used in SR25 platforms. The length and some mounting points may vary depending on the replica manufacturer, so compatibility should be checked before installation.

Compatibility

Component Compatibility
HPA Engine PolarStar F2 specifically for SR25
Hop-up Chamber Silent Industries ALPHA
Base Replica SR25 AEG
Gearbox V2.5 / Extended V2
Configuration HPA / DMR

Important: Use the PolarStar F2 nozzle version corresponding to your SR25 platform. The nozzle length must match the chamber, bucking, and gearbox being used.

What the Kit Includes

  • Rear clip for mounting using the rear pin or fixed stock.
  • Alignment base for the Silent Industries ALPHA chamber.
  • Housing for M3 inserts.
  • Side clip for HPA line routing.
  • Upper front chamber locking cap.
  • Rear plate with mounting point for an M5 screw.
  • Support elements to keep the nozzle and chamber position stable.

System Benefits

  • Keeps the PolarStar F2 nozzle centered relative to the chamber.
  • Reduces lateral movement of the chamber during firing.
  • Improves feeding stability in SR25 HPA configurations.
  • Helps maintain consistent pressure between the nozzle, bucking, and chamber.
  • Reinforces the mounting area on DMR platforms with long inner barrels.
  • Allows the ALPHA chamber to be used with a dedicated alignment structure.

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 there are no burrs that could shift the chamber.
  • If necessary, use dry lubricant or wax on sliding surfaces.
  1. Installation in the Replica
    • Place the base in the lower receiver of the SR25 replica.
    • Install the M3 inserts into the designated housings.
    • Install the Silent Industries ALPHA chamber together with the inner barrel.
    • Install the rear clip using the rear pin or stock mounting system.
    • Route the PolarStar F2 HPA line through the side clip.
  2. Nozzle Alignment
    • Check that the SR25-specific nozzle is centered with the chamber entrance.
    • Verify that the nozzle moves in and out without rubbing or lateral pressure.
    • Check that the chamber maintains stable contact with the bucking.
    • If there is lateral play, inspect the chamber seating and perform very light sanding if necessary.
  3. Final Securing
    • Install the rear plate and use an M5 screw with washer to increase rigidity.
    • Check that the inner barrel remains centered and does not move.
    • Perform feeding tests with the magazine installed.
    • Adjust the hop-up and PolarStar F2 settings progressively.

Required Components (Not Included)

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

Assembly Recommendations

  • Use the PolarStar F2 nozzle specifically designed for SR25.
  • Check the nozzle length before closing the replica.
  • Do not force the chamber against the nozzle; there should be proper contact without excessive pressure.
  • Verify compatibility between the lower receiver, V2.5 gearbox, and installed chamber.
  • On SR25 platforms, pay particular attention to magazine positioning and BB feeding.
  • Perform initial tests at low pressure and gradually increase the settings.

Lower Receiver Recommendations

A metal ICS lower receiver or a lower receiver with sufficient structural rigidity is recommended to prevent movement between the gearbox, chamber, and inner barrel.

If you prefer to print your lower receiver, these Gearbox v2 Lower "Universal Lower" models may be useful for different configurations:

  • Version 3
  • Version 4.2
  • Version 4.3 MTW

You can find them HERE.

Lower receiver compatibility should be checked according to the specific SR25 model, body manufacturer, and type of V2.5 gearbox installed.

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%
  • Orientation: Depending on the part