Newly designed, extremely strong and, compared to metal outer barrels, very light outer barrel for AR15 (M4) style airsoft replicas. The dominant part of the barrel – the carbon fibre tube ③ with a thickness of 2 mm and a diameter of 19 mm – is very strong, light and will give your replica a unique look. The tube is made by laminating carbon cloth and is not an imitation in the form of a print on a plastic tube. The 3K designation stands for the type of carbon fiber cross-linking.
In the front part there is a duralumin end cap ② made of aviation duralumin 7075 with a standard M14 x 1mm CCW (left-hand) thread. If a right-hand thread is required, a reduction to a right-hand thread M14 x 1mm (9403) must be used. On both ends of the barrel there are integrated o-rings ⑩ (8.5 x 1mm) for centering the inner barrel.
The carbon tube is filled with acoustic layered fabric inserts ⑫, which has a smaller inner diameter than the outer diameter of the inner barrel, which prevents the inner barrel from vibrating during firing and, at the same time, does not transmit the noise of firing to other parts of an airsoft replica.
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, which press the chamber to the gearbox through the pressure ring and thus prevent the Hop Up chamber from bouncing when firing (how it works - video). At the same time, this prevents unwanted air leaks between the nozzle and the Hop Up rubber band. The thrust ring ⑥ is CNC-turned from C45 steel and heat-treated to high hardness to prevent deformations from the set screws, as this wedge system has a very high clamping force. The thrust ring is sprung ⑤ so that it is always in the correct position during assembly. The pressure ring is secured from the side with two setscrews ⑧ so that it does not fall out during handling. In order to prevent the transfer of hard shocks from firing, it is important to put an o-ring ⑪ (8.5 x 2mm 70Sha) on the front part of the Hop Up chamber. In case of RetroArms Hop Up chamber for AR15 (6388) 1 pc o-ring is needed. With other manufacturers of Hop Up chambers, due to the different lengths of the Hop Up chamber, it is necessary to measure the length and possibly add another o-ring, and thus the proper functioning of the down pressure cannot be guaranteed. In addition, the RetroArms AR15 Hop Up Chamber (6388) has a collet nut (6778) that has an enlarged front surface and thus does not tend to cut on the ring as is the case with Hop Up chambers without this collet.
On the main body of the outer barrel, there are 3 M2.5 threads around the perimeter for installation of the positioning screws ⑨. For AR15 RetroArms bodies, all 3 pieces of positioning screws are installed. Between the main body and the carbon tube, there is a decoration ring ④ made of aviation duralumin 7075, which improves the overall attractiveness of the barrel.
The outer barrel is delivered completely assembled. The carbon tube is threaded and glued to the aluminium parts at the factory with PUR glue to ensure maximum rigidity of the barrel.
When installing an inner barrel with a Hop Up chamber into an outer barrel, it is important to remove the centering o-rings from the inner barrel, if they are fitted to the inner barrel. Before inserting the inner barrel, it is also necessary to loosen the set screws ⑦. Tightening of the set screws ⑦ is done only after the replica is fully assembled. The set screws are tightened with a tightening torque of max. 0.5 Nm.
