TubeRA is an innovative combination of simplicity and functionality. It fully replaces the standard handguard and also functions as a silencer. Thanks to the materials used (7075 Aluminium and carbon fibre) this handguard is both exceptionally strong and light.
There are two types of inserts in the package: Acoustic and Centering. The set of acoustic inserts is used for sound dampening and two centering inserts are used to stabilize the inner barrel. The inserts can be combined based on player's preference and/or the length of the inner barrel used.
TubeRA with 363 mm inner barrel:
TubeRA with 247 mm inner barrel:
An additional feature on this handguard is the hop mount system, which is identical to the system found on our outer barrels.
In the main body ① of the outer barrel (made of aviation duralumin 7075), there is an integrated Hop Up chamber pressure mechanism. The pressure of the Hop Up chamber is controlled by a wedge clamp using two set screws ⑦. These screws press the chamber against the gearbox through a pressure ring preventing the Hop Up chamber from bouncing during firing (see video for demonstration). This aslo helps to prevent unwanted air leaks between the nozzle and the Hop Up rubber band. The thrust ring ⑥ is CNC-machined from C45 steel and heat-treated for high hardness preventing deformations from the set screws, due to the high clamping force of the wedge system. The thrust ring is spring loaded ⑤ to ensure it remains in the correct position during assembly. The pressure ring is secured from the side with two set screws ⑧ preventing it drom falling out during handling. In order to prevent the transfer of hard shocks from firing, it is important to place an O-ring ⑪ (8.5 x 2mm 70Sha) on the front part of the Hop Up chamber. In the case of RetroArms Hop Up chamber for AR15 (6388) one pc O-ring is required. This Hop Up Chamber has a collet nut (6778) with an enlarged front surface which prevents the O-ring from being cut - an issue common in chambers without this feature.
Due to variations in Hop Up chambers from other manufacturers, it is necessary to measure the length and possibly add an additional O-ring. Therefore the proper functioning of the downforce cannot be guaranteed out of the box. The indexing wing cutouts are designed to be compatible with RetroArms Hop chambers and compatibility with other manufacturers is not guaranteed.
The main body of the outer barrel includes three M2.5 threads around its perimeter for installation of the positioning screws ⑨. For AR15 RetroArms bodies, all three pieces of positioning screws are used.
Before installing the TubeRA body, the set screws ⑦ should be adjusted. Hold the main body ① of the outer barrel in place by hand and tighten the set screws ⑦ until the Hop Up chamber is held securely against the gearbox. Once secured, the rest of the TubeRA can be screwed on.
