Retro Arms CNC AR-15 Ultra Hop-Up Chamber

The ultimate solution for players, who want a fully customizable Hop Up chamber.

Hop Up chamber ULTRA is also based on our chamber BASIC and is also made on precise CNC machines from aviation grade aluminium 7075. This chamber also has the adjustable feeding shaft as the chamber PRO.

New features include adjustable nozzle shaft, which is meant to be used to make the chamber sit more forward, when necessary. This feature is really helpful for tuning the longitudinal position of the chamber and thus e.g. adjusting the reliability of feeding, or position relative to the magazine. The position can be adjusted by 0.2 mm increments with included shims. Bear in mind that this feature also requires use of different length nozzles. The adjustable nozzle shaft will be offered with multiple outer diameters for you to choose the best option according to your GB shell.

The next ULTRA feature is the inner barrel securing mechanism. Compared to the standard solution, we completely redesigned this mechanism, to mitigate the main fault - the C-clip cannot hold the barrel in place (longitudinal movement and rotation).

This new system consists of a reshaped C-clip made of POM, and a custom union nut, which holds the C-clip tightly to the barrel and is also precisely machined to be able to reliably center the inner barrel. With this solution, the C-clip cannot twist loose with barrel rotation and the barrel cannot move longitudinally, because it is tightened with the union nut. Tighten the nut only by hand! The union nut has a maximal outer diameter of 12.95 mm, which should fit into the majority of outer barrels, but make sure it can fit before purchase.

Another difference is the main shaft shape in the ULTRA chamber. Compared to chambers BASIC and PRO, the shape of the drilling is adjusted in the area where the Hop Up rubber sits. It is made flat and standard AEG rubbers are meant to be used with included rings. Those rings fill in the material, which is missing and can be adjusted e.g. by sanding to compensate for different hop up rubbers dimensions. Another reason for this drilling is to allow use of our new ROBUST hop up rubber.