EMG x Retro Arms CZ Billet CNC 8mm Ver.2 Gearbox Shell for M4 / M16 Series Airsoft AEG Rifles

The EMG x Retro Arms CZ Billet CNC 8mm Version 2 Gearbox Shell represents the ultimate upgrade for serious Airsoft builders who demand performance, precision, and durability. Crafted through a collaboration between EMG (Evike Manufacturing Group) and Retro Arms CZ, this gearbox is a masterpiece of engineering — precision-machined from a single block of EN AW 7075 T651 aircraft-grade aluminum, giving it strength far beyond traditional cast or die-forged shells.

This is not your average gearbox. Designed to handle extreme builds and high-stress performance setups, the EMG x Retro Arms CZ Gearbox is capable of withstanding M160 spring loads without showing signs of fatigue or structural failure. Whether you’re fine-tuning your AEG for high-speed or high-torque builds, this shell gives you the solid foundation you need for reliable, long-lasting performance.

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Unmatched CNC Precision and Strength

Each gearbox shell is precision CNC-machined from a billet block of EN AW 7075 T651 aluminum, one of the strongest aluminum alloys available, commonly used in aerospace and military-grade applications. This billet machining process ensures unparalleled dimensional accuracy, rigidity, and a perfect fit for internal components — key factors for consistent performance and reduced wear over time.

The durable anodized finish not only enhances corrosion resistance but also gives the shell a premium matte look worthy of its engineering pedigree. Every shell is laser-engraved with the EMG logo, a mark of authenticity and quality craftsmanship.

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Reinforced for High-Stress Builds

Unlike standard cast gearboxes that can crack under heavy spring tension, the Retro Arms CZ design reinforces key stress points to handle the most demanding builds. The gearbox has been extensively tested with M160 springs — an impressive testament to its durability and mechanical integrity.

The pre-radiused cylinder windows further distribute stress evenly, minimizing cracking risks and extending the shell’s lifespan. Combined with stainless steel connecting bolts and precision tolerances, this gearbox remains rock solid even under the heaviest loads or fastest rates of fire.

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Quick-Change Spring Guide System

One of the standout features of this gearbox is its Quick-Change Ball Bearing Spring Guide System. Unlike traditional designs that require full disassembly to swap springs, this mechanism allows you to change your spring in minutes — perfect for tuning FPS limits or optimizing for field regulations.

This feature is especially valuable for players who alternate between CQB and outdoor environments, allowing effortless transitions between different power levels.

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Optimized Design and Compatibility

Every aspect of the EMG x Retro Arms CZ gearbox is optimized for functionality and user convenience. The deeper wire channels along the base provide easier cable routing and protect your wiring during installation.

The 8mm bearing/bushing compatibility allows smoother gear rotation and enhanced mechanical efficiency — a must-have for high-performance setups. This gearbox is compatible with Tokyo Marui, G&P, Matrix, and other M4 / M16 Series AEG platforms (minor modification may be required depending on your specific model).

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Professional-Grade Construction

This gearbox shell is designed for experienced Airsoft technicians, builders, and enthusiasts who demand the best. The tight tolerances and robust construction make it ideal for pairing with high-end internals, HPA conversions, or DMR builds that push mechanical limits.

Disclaimer: Professional installation is recommended, as fitment may vary depending on manufacturer tolerances and model variations.

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Specifications:

• Manufacturer: EMG x Retro Arms CZ

• Material: CNC Billet EN AW 7075 T651 Aluminum

• Compatibility: Tokyo Marui, G&P, Matrix, and other M4/M16 Series AEGs (Modification may be required)

• Bearings/Bushings: 8mm

• Features: Quick-Change Spring Guide, Reinforced Design, Deep Wire Channels, Pre-Radiused Cylinder Windows

• Finish: Hard Anodized

• Logo: EMG Engraved Branding

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Why Choose the EMG x Retro Arms CZ Gearbox?

✅ Machined from solid billet aluminum for maximum strength
✅ Reinforced for high-tension springs (tested up to M160)
✅ Quick-change spring guide system for rapid tuning
✅ Pre-radiused cylinder windows for stress distribution
✅ Deep wire channels for cleaner, safer wiring
✅ Designed for precision builds and pro-level performance

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About EMG

EMG (Evike Manufacturing Group) was founded to bring next-level innovation and precision to the Airsoft market. Partnering with leading manufacturers like Retro Arms CZ, EMG’s goal is to create products that push the limits of performance and realism.

With deep industry knowledge, global partnerships, and a passion for perfection, EMG delivers parts and replicas that stand out in both engineering and quality — products that live up to their promise of “Manufacturing Excellence in Airsoft.”