[RETRO ARMS] CNC Hop Up Chamber AR15 ULTRA

*Note*
The maximum outer diameter of the part that goes into the outer barrel is Φ12.95mm. It fits most outer barrels, but
It is 1mm thicker than the genuine Tokyo Marui product, so please check before use.


Since the shape is different from the UNI version before the minor change, it cannot be attached to the CNC Split Gearbox V2 with int. Hop Up Chamber UNI - QSC (8mm) or earlier V2 gearboxes with integrated chambers.

This is a standard electric AR15/M4 chambered from EN AW7075-T651.
It can be used with the company's V2 series gearbox and Tokyo Marui-compliant Ver.2 gearbox.

The hop dial is a stepless adjustment type with O-ring tension.
The hop lever is a seesaw type that uses regular cushion rubber.
Two types are included: a vertical direct press type for long hops such as R-HOP.

The ULTRA has separate parts for the bullet feed pipe and nozzle inlet.
By inserting the included shims, you can fine-tune the length of the feed pipe and the distance between the gearbox and chamber.

In all cases, the reference dimensions are those without any of the included shims.
Each shim is 0.2mm x 5 pieces, which can stretch it by a total of 1mm.
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The barrel is secured using a dedicated C-clip (included and spares available separately ).
It uses a unique method that ensures it is pressed securely against the rear of the chamber.
Tighten the red nut parts as tightly as possible by hand.
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2025.5.19 Update
The nozzle has a thin tip of 7.2mm or less and a thick base of 8mm or less.

The recommended nozzle length is 21.3mm in accordance with the company's CNC Nozzle if the gearbox, receiver, and outer barrel are all manufactured by the same company .
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The biggest feature of this chamber is that you can switch the shape of the compatible hop-up pad.
By inserting the red spacer parts, you can use conventional standard electric gun hop-up pads.
By removing the spacer parts, you can use RETRO ARMS' original ROBUST type hop-up padding.

The ROBUST type does not have an airtight lip like the Tokyo Marui electric handgun, next-generation Mk46, or next-generation MP5.
The thick shape is intended to improve airtightness, prevent bullets from getting caught when being fed, and suppress excessive shape changes when fired.
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Ten spacer O-rings are included to fill the gap between the outer barrel and the chamber and press it against the gearbox with elasticity.
Adjust the number according to the gap.

In addition, GAW general-purpose piston/spring guide spacers for Φ13mm springs (various bolt action large diameter springs) can be used as spacers with a thickness of 2mm per piece.

One thing to note about this chamber is that its overall length is 6.7mm shorter than the previous BASIC and PRO models.
If the setting is BASIC or PRO, be sure to adjust it with a spacer.