Remade and upgraded CNC gearbox from Retro ARMS with code name "7075 series". 8mm - black anodising, 9mm silver anodising.

Gearbox version II is completely milled at CNC machining center. Compared to other aluminium gearboxes, our is made out of solid block of aluminium AW EN7075 T651. Source block weighs 1550g and only 143g of material are left. It is not casted like Chinese ones! Our gearbox is tested wit M160 spring without any signs of wear or breaking long term. Gearbox's surface is decoratively anodized.

It's available with slots for 8mm. Bearings are not included. You can choose them from our offer here.

Gearbox is equipped with quick spring change system - QSC. Our CNC spring guide is included.

New features and upgrades:

• reduction of wall thickness - it can be used in most of M4 guns without problems
• reduction of plugs for cylinder head (1) - cylinder heads from all makers can be used
• сделаны for bigger air flow (2)
• control window for AOE (3)
• control window for piston position check (4)
• removing of radiuses around place for trigger contacts - ASCU contacts can now be used without problems (5)
• widening of hole for central pin - gearbox can be installed into non-standard bodies e.g. PJ (6)
• windows for lubing gears (7)
• opening for releasing anti-reversal latch (8)
• remade holes for using screws with cylindrical heads + new strength screws (9)
• new wrought threads - compared to old cut ones
• go-through window for cables under motor post (10)
• milled shoulder above motor cables under motor post (11)
• more edges bevelled by machine
• adjusted front part of the gearbox allowing use of more Hop Up Chamber types (12)
• new strength screws

All standard parts for gearbox version II can be used of course. Both halves fit together with absolute precision including bearing holes,
which are 100% co-axial.

Further small features:

• accurate hole for Anti-Reversal Latch - it doesn't fall out
• accurate hole for trigger - it doesn't jump out even with strong spring
• micro grooves on pins, which hold trigger trolley spring a tappet plate spring - springs don't jump out

Package includes 1 x gearbox version II, 2 x screw M2.5 x 3, strength screws, CNC spring guide and Retro ARMS sticker.

Gearbox comes with lifetime guarantee against breaking. It doesn't relate to breaking caused by misused parts, e.g. improper cylinder head.

We try to adjust our gearboxes as much as possible to allow use of the widest variety of part brands. However we still recommend to use Retro ARMS spare parts, because they are the most compatible.

We can't recommend our gearboxes in Classic Army Guns due to problems with compatibility.