MDRX GUIDE - Silverback MDRX

The complete guide to the Silverback MDRX: every component explained, the best upgrades, and what makes this bullpup AEG unique. The MDRX is a modular bullpup with an electronic trigger system, dual caliber capability (5.56 & 7.62), and APS2 compatible springs — all in a compact, lightweight package. You can upgrade progressively or all at once — and if you prefer, we install the upgrades for you.

Table of Contents

1. Why the MDRX?
2. MDRX Variants
3. ECU & Electronics
4. Hop-Up System
5. Inner Barrel
6. Pistons & Cylinders
7. Springs
8. Outer Barrels
9. Body & Customization
10. Magazines & Caliber Conversion
11. Maintenance
12. Upgrade Path
13. Collections

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1. Why the Silverback MDRX?

The Silverback MDRX is a bullpup AEG platform that stands apart from conventional assault rifles. Designed by Silverback Airsoft, it combines innovation and modularity in a package that very few replicas can match:

• Bullpup layout — The gearbox sits behind the trigger, resulting in a significantly shorter overall length while maintaining a full-length barrel. Ideal for CQB and tight spaces without sacrificing range
• Electronic trigger (ECU) — No mechanical delay. The electronic control unit provides instant trigger response with selectable semi-auto and full-auto modes
• Modular caliber system — Switch between 7.62 (AR10 magazines, 78bb) and 5.56 (AR15 magazines, 120bb) with the magazine adapter and corresponding mag catch. Two platforms in one
• Lightweight & compact — Polymer receiver, bullpup design. One of the lightest and most manoeuvrable AEGs on the market
• APS2 compatible springs — The same 13mm springs used in the SRS and TAC-41. Change power in seconds
• Quick-change barrel system — 16” standard and 10.5” Micron outer barrels are swappable

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2. MDRX Variants

The MDRX comes in three main configurations: V3 (latest generation), V2, and Micron (compact). All share the same internal architecture and are fully compatible with the same upgrades.

MDRX V3 — 604.95€

The latest generation. Improved ECU V3, refined trigger response, and updated internals. The definitive MDRX. Available in three colours:

MDRX Micron V3 — 604.95€

The compact variant with a 10.5” barrel instead of 16”. Same V3 internals in an even shorter package. Perfect for CQB and indoor fields:

MDRX V2 — 598.95€

The previous generation. Still an excellent platform with proven reliability. A solid choice at a slightly lower price point:

V2 vs V3 — Key Differences

Feature	V2	V3
ECU	Standard trigger board	ECU V3 with improved MOSFET
Gearbox	V2 spec	V3 spec with 18:1 steel gears
Piston	Standard piston head	V3 piston head
Spring guide	Standard	V3 spring guide
Price	598.95€	604.95€

Standard vs Micron

Feature	Standard (16”)	Micron (10.5”)
Outer barrel	16” with gas block	10.5” with gas block
Handguard	Full-length 16”	Compact Micron
Inner barrel	~420mm	~265mm (shorter)
Best for	Outdoor, range	CQB, indoor

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3. ECU & Electronics

The MDRX uses an Electronic Control Unit (ECU) instead of a mechanical trigger system. This is one of the key advantages of the platform — instant trigger response with no mechanical delay or creep.

ECU V3 — The Brain of the MDRX

The ECU V3 is the latest generation electronic trigger board. It manages motor control, provides MOSFET protection, and delivers crisp trigger response:

Trigger Unit

The trigger unit is the physical trigger mechanism that interfaces with the ECU. The electronic contact board translates your trigger pull into a signal:

Fire Mode Control

The MDRX supports selectable fire modes via interchangeable control caps on the trigger unit:

• Semi/Full — Standard fire selector with semi-automatic and full-automatic modes
• Semi Only — Locked to semi-automatic only, required by many CQB fields

Gearbox & Anti-Reversal

The MDRX V3 uses 18:1 steel gears for reliable cycling and durability. The anti-reversal latch prevents the gears from spinning backwards:

▶ Trigger control caps

silverback-mdrx-trigger-unit-control-caps

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4. Hop-Up System

The MDRX uses an AEG-type hop-up system with a flat hop bucking. While bolt-action snipers like the SRS and TAC-41 use concave buckings and TDC chambers, the MDRX follows the AEG convention — but it still delivers excellent accuracy thanks to its quality components.

Hop-Up Chamber

The MDRX hop-up chamber is a proprietary design. Replacement units are available:

Hop-Up Bucking

The stock bucking is an 80° flat type (red) — a good all-round choice for AEG use. It provides consistent backspin without over-hopping:

Nubs

The stock nub presses the bucking against the BB. Replacement nubs are available:

Drop-in Morpheus Compatibility

The MDRX hop-up is compatible with Stalker Morpheus inner barrels. The Morpheus 420mm is a direct drop-in upgrade for the standard 16” MDRX:

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5. Inner Barrel

The inner barrel is where accuracy is born. The Stalker Morpheus 420mm is the reference upgrade barrel for the standard MDRX. Made from carbon steel with a precision AEG bore, it is designed to work as a system with the hop-up chamber and flat hop bucking.

Stalker Morpheus AEG 420mm

The premium upgrade barrel for the MDRX 16” variant. Drop-in installation with immediate accuracy improvement:

• Precision bore — Tight tolerance for consistent BB flight
• Carbon steel construction — Durable and smooth interior
• 420mm length — Perfect fit for the standard 16” outer barrel
• AEG type — Compatible with the MDRX hop-up chamber

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6. Pistons & Cylinders

The MDRX gearbox uses a proprietary piston and cylinder system. Understanding the options allows you to fine-tune power delivery and air seal.

Piston (16 Teeth)

The MDRX uses a 16-tooth piston that meshes with the 18:1 gears. The V3 version includes an upgraded piston head:

Cylinder Options

The MDRX offers two cylinder configurations that directly affect power output:

• Ventilated 75% (stock) — The stock cylinder has a port that releases 25% of the air volume. This reduces power for indoor/CQB use and comes installed from the factory
• Closed 100% — A fully sealed cylinder that delivers 100% of the air volume. Use this for maximum power output with heavier springs

Tip: If you want more power without changing the spring, swap the ventilated 75% cylinder for the closed 100%. This alone can add significant joule output.

Cylinder Head & End

The cylinder head includes the integrated nozzle. The cylinder end caps the rear:

▶ Piston accessories

silverback-mdrx-piston-guide-ring-x2,silverback-mdrx-piston-head-o-rings-x5,silverback-mdrx-cylinder-head-o-rings

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7. Springs

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Rapax springs come in two formats:

• APS2 — Standard format, longer. Compatible with all MDRX models
• RMS (Rapax Match System) — Shorter, designed for greater adjustability. Includes ABS spacers as standard for fine FPS tuning. More compatible with power rings

Rapax	Power	Type	Price
APS2 1J	~1.0J	APS2	19.95€
APS2 2+	~2.0J	APS2	19.95€
RMS 2+	~2.0J	RMS	19.95€
2.8J	~2.8J	APS2	17.95€
APS2 3+	~3.0J	APS2	19.95€
RMS 3+	~3.0J	RMS	19.95€
RMS 4+	~4.0J	RMS	19.95€
APS2 4+	~4.0J	APS2	19.95€

FPS Adjuster Rings (Power Rings)

The steel FPS adjuster rings from Rapax let you tune power without changing or cutting the spring. They install on the spring guide as preload washers.

▶ Spring guides and pins

silverback-mdrx-spring-guide,silverback-spring-guide-v3-mdrx,silverback-mdrx-spring-pin-set-x5

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8. Outer Barrels

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One of the MDRX's most unique features is its dual caliber system. The rifle natively uses 7.62 AR10 magazines (78bb) but can be converted to 5.56 AR15 magazines (120bb) with an adapter and the corresponding mag catch.

7.62 AR10 Magazines (78bb) — Native

The stock magazine configuration. Shorter, wider magazine with 78bb capacity:

5.56 AR15 Magazines (120bb) — With Adapter

Higher capacity magazines using the AR15 form factor. Requires the magazine adapter and 5.56 mag catch:

Caliber Conversion Components

To convert from 7.62 to 5.56 (or vice versa), you need:

1. Magazine adapter — Adapts the magwell to accept AR15 magazines
2. 5.56 mag catch — Aluminum mag catch designed for the narrower AR15 magazine

Mag Catches

Each caliber requires its specific mag catch:

• 7.62 Steel Mag Catch — For stock AR10 7.62 magazines
• 5.56 Aluminum Mag Catch — For converted AR15 5.56 magazines

▶ Followers and replacements

silverback-mdrx-follower-replacement-5-pack,silverback-follower-tac-mdrx-magazine

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11. Maintenance

The MDRX is a robust platform but like any AEG, it benefits from regular maintenance. Here are the key maintenance items:

O-Ring Replacement

O-rings wear over time and can cause air leaks. Keep spares on hand:

Screw Sets

Screws can loosen during play. Having replacement sets ensures you never lose a critical fastener:

Tools

Specialised tools for MDRX maintenance:

• Cylinder Head Wrench — For removing and tightening the cylinder head with integrated nozzle
• Pin Removal Tool — For safely removing the rail system pins during disassembly

Nozzle Assembly

The nozzle assembly and feeding tube are wear items that may need replacement:

General Tips

• Inner barrel cleaning — Run a cleaning rod with a microfibre patch every 5-10 game days
• Gearbox lubrication — Use quality silicone grease on gears every 3-4 months
• O-ring check — Inspect cylinder and piston O-rings for wear when FPS becomes inconsistent
• Battery care — Use a quality LiPo charger, never over-discharge

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12. Upgrade Path — Progressive Buying

You don't need to buy everything at once. The MDRX can be improved gradually. Here's the recommended order, from highest to lowest impact:

1. Hop-up bucking — The flat hop 80° bucking is already good, but a quality replacement can tighten groupings immediately
2. Inner barrel (Morpheus 420mm) — The single biggest accuracy upgrade. Precision bore with consistent BB flight
3. Cylinder (closed 100%) — Swap the ventilated 75% for the closed 100% to increase power output without changing the spring
4. Spring — Adjust power to your field's rules. APS2 springs swap in seconds
5. Outer barrel — Switch between 16” and 10.5” configurations to change the rifle's role
6. Body customization — Receivers, grips, stocks and handguards for aesthetics and ergonomics

We install upgrades for you — if you buy the parts at Skirmshop, we can install them in your MDRX. Contact us for more information.

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13. MDRX Collections

• MDRX Electronics
• MDRX Buckings
• MDRX Barrels
• Stocks & Accessories
• Spare Parts & Kits
• Pistons & Cylinders
• Hop-Up & Parts
• Body & Parts
• Muzzle Devices & Barrel Accessories
• Springs
• Grips