Retro ARMS 2025 V2 Gearbox Shell for E&L M4 8mm

CNC Gearbox V2 (8mm) – QSC CNC gearbox V2 is intended to be used with airsoft replicas of AR15 (M4), M16, MP5 and other rifles with V2 gearboxes. Our gearbox is manufactured from a single block of aviation grade duralumin EN AW 7075 T651, which has greater tensile strength (590 MPa) than standard structural steel (390 MPa). Thanks to this material our gearbox shell has several times longer lifespan than standard zinc-alloy gearbox shells. Our gearbox shells are manufactured on precise CNC machines directly in our company in the Czech Republic (EUROPE). The number in the brackets (e.g. (8mm)) describes the diameter of the holes for bushings / bearings. The gearbox is equipped with Quick Spring change (QSC) system, thanks to which you can remove the spring without the need of disassembling the gearbox. With this solution it is necessary to secure the spring guide with a screw, which is done by buffer tube screw as standard, or you can use QSC screw if securing with buffer tube screw is not possible / desired. If you leave the spring guide unsecured, the spring will twist with compression, misalign the spring guide and cause gearbox jam with damage to the piston, gears, motor and gearbox shell. CNC gearbox is possible to install into airsoft replicas of Tokyo Marui standard and is possible to be fitted with components of Tokyo Marui standard. While installing the inner parts into the gearbox, and the gearbox into the gun, never use brute force. For tightening the screws use max moment 1.2 Nm, or the threads will be stripped. If you want to be certain that the screws won't get loose, threadlock could be used. Spring of any strength can be installed into our gearbox. Installation of the inner parts as well as installation of the shell into the gun can be tricky and requires professional knowledge, experience and skill. Because of plethora of different manufactures which are copying from each other and rounding the dimensions of components, there are no standards in airsoft (such as EN, ISO, etc.). This is why our gearbox shell can be plug-and-play in some replicas but struggle to install in others. We did our best to come as close as possible to TM original while improving the shell with little features, such as tongue for wires under pinion gear, little windows for easier gears height adjustment, set screws on the side of the shell for gearbox alignment etc. Little features for QoL improvements: All little springs (trigger, safety, AR latch, tappet plate) are always held in some kind of notch, mitigating their tendency to pop off, especially while disassembling Window for AoE check Bearing holes are smaller by .02 mm in diameter, to better secure the bearing in place. Holes are also equipped with ANTIROT pockets for glue / ANTIROT bushings. For easier bearings installation you can download, and 3D print our tool. Wire routes are enlarged Tongue for wires under pinion gear All threads are formed (threads are stronger) Halves of shell are centered by tabs around the gearbox Window to disengage AR latch Even more reinforced area around cylinder head Changelog What is new in the 2025 version Pinion-to-Bevel gear meshing reviewed. It took us some time, but after lots and lots of thinking, measuring and testing we slightly repositioned and realigned the motor tower hole and optimized bearing holes positions. Sector gear hole did not move, but spur and bevel gear holes are moved by orders of hundreds of millimeters away from each other. This change ensures better compatibility with gears of different manufacturers. Hole for the motor tower (which was moved almost by 0.1 mm), is now better aligned with the bevel gear axis while maintaining 118° angle as before. Longer nozzle stroke. We allowed tappet plate to move more forward by 0.3 mm, which allows for shorter nozzles to be used for more reliable feeding, or nozzles with same length to have better air-seal Improved Cylinder housing. Redesigned cylinder housing, so that cylinder sits on 8 support tabs instead of full-length rails and thus ensuring better compatibility with more manufacturers and easier installation and tuning. Improved details around bevel gear to support bigger wires. Improved bushing/bearing holes. We know that most of you like to glue bushings or bearings in place, so we prepared "glue pockets". With those you can either glue standard bearings/bushings, or you can use our new ANTIROT bushings which click right into those pockets. Distinctive detailing of our Gearbox. Because you want not only fully working gearbox, but also nice and 100% finished product. Enlarged radius at the front of the gearbox. It means that now it is tougher, and more resistible against cracking.  Redesigned piston rail. For longer gearbox life. Redesigned rails for selector plate. Compatibility with more manufacturers. Piston position windows. Redesigned space around sector gear. Compatibility with more manufacturers and more gear ratios. More wire routing optimization. Longer wire guide rails which are now also completely shielding path for ambidextrous fire selector. Added tab for COMPRING anti-reversal latch Package contains: CNC gearbox shell, QSC spring guide, screws set.