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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. 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 also 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 from 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. Our Hop Up Chambers have a collet nut (6778) that has an enlarged front surface which prevents the O-ring from being cut - an issue common on 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 proper functioning of the downforce cannot be guaranteed out of the box. Indexing wing cutouts are designed to be compatible with RetroArms Hop Up chambers and compatibility with other manufacturers is not guaranteed.
The main body of the outer barrel includes three M2.5 threads around its the perimeter for installation of the positioning screws ⑨. For AR15 RetroArms bodies, all three pieces of positioning screws are used. 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.
We have prepared a simple printable model for you to help you with the barrel assembly. It's a simple aid to hold the thrust ring ⑥ in place while you screw in the setscrews ⑧. Just hold the aid in the main body to compress the spring and align the ring in place and screw in the setscrews.
BARREL ASSEMBLY AID [STEP]
BARREL ASSEMBLY AID [STL]
