backdraft phoenix retroarms alignment kit v2 1 m4 ar

Version 2.1 of the hop-up alignment system, designed for M4 / AR-15 AEG HPA replicas and ICS split platforms that use:

• Backdraft PHOENIX HPA Engine (high-performance modular HPA engine with more than 40 RPS and a wide pressure range).
• RetroArms CNC Hop-Up AR15 / M4 chamber (rotary hop-up chamber in 7075 CNC aluminum, designed for maximum precision and air seal).

This kit ensures exact centering between the PHOENIX nozzle and the RetroArms chamber, taking advantage of their tight tolerances to improve sealing, feeding consistency, and precision in demanding HPA builds.

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Compatibility

Element	Compatibility
HPA Engine	Backdraft PHOENIX M4 / V2
Hop-up chamber	RetroArms CNC Hop-Up M4 / AR-15
Base replica	M4 / AR-15 AEG, ICS M4
Gearbox	Standard V2 / ICS V2 split
ICS metal lower	Fully compatible

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What the kit includes

• Rear clip for mounting using rear pin or fixed stock.
• Base with housing for M3 inserts (optional in brass for maximum rigidity).
• Side clip for guiding the PHOENIX HPA line.
• Upper front locking cap, adapted to the RetroArms CNC body and the threaded barrel / C‑clip system.
• Rear plate with fixing point for M5 screw that reinforces the assembly.

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Installation and adjustment

1. Printing and preparation

   • Print the parts with infill between 65-80 %.
   • Gently sand the internal areas and contact surfaces to achieve a snug fit.
   • You can apply dry lubricant or wax to the sliding areas to facilitate assembly and maintenance.

2. Assembly in the replica

   • Insert the base into the lower (ICS metal or printed universal) and mount the M3 inserts.
   • Place the rear clip aligned with the rear pin or the stock anchor.
   • Install the RetroArms chamber with the inner barrel; the upper cap fixes the position and helps keep the barrel centered to take advantage of the CNC sealing of the chamber.
   • Guide the HPA line of the PHOENIX through the side clip to avoid sharp bends or pinches in the hose.

3. Final fixing and testing

   • Fix the rear plate with an M5 screw and washer for maximum rigidity.
   • Adjust the working pressure of the PHOENIX within its range (approx. 40-130 PSI) and verify that the nozzle feeds constantly without marking the BBs.
   • Perform shooting tests and correct the hop‑up with the RetroArms rotary wheel until you obtain the desired trajectory.

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Required components (not included)

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

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Lower recommendations

It is recommended to use the ICS metal lower for maximum rigidity and durability, especially in high-pressure HPA configurations.

If you prefer to print the lower part, these Gearbox v2 Lower "Universal lower part" models are compatible with this kit:

• Version 3
• Version 4.2
• Version 4.3 MTW

You can find them HERE.

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3D printing parameters

• Approximate printing time: ~1 h 30 min
• Recommended material: PLA+
• Layer height: 0.10 mm - 0.15 mm

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Manuals

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