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
- Why the MDRX?
- MDRX Variants
- ECU & Electronics
- Hop-Up System
- Inner Barrel
- Pistons & Cylinders
- Springs
- Outer Barrels
- Body & Customization
- Magazines & Caliber Conversion
- Maintenance
- Upgrade Path
- Collections
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
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 |
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
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:
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
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% (de serie) — 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
7. Springs
The MDRX uses APS2 compatible springs — the same 13mm springs used in the SRS and TAC-41. This means the entire Silverback and Rapax spring ecosystem is available for power tuning.
Silverback Springs (Stock)
| Spring | Power | Use | Price |
|---|---|---|---|
| APS 60N | ~0.8-1.0J | CQB | 12.25€ |
| APS 90N | ~1.0-1.3J | CQB+ | 15.15€ |
| APS 100N | ~1.3-1.5J | Light outdoor | 15.15€ |
| APS 120N | ~1.5-1.8J | Outdoor | 15.15€ |
| M130 | ~1.7-2.0J | DMR | 12.05€ |
| M140 | ~1.9-2.2J | DMR | 11.90€ |
| APS 150N | ~2.0-2.5J | Open field | 15.15€ |
| M160 | ~2.5-3.0J | High power | 11.95€ |
| M170 | ~3.0-3.5J | Maximum power | 11.90€ |
Note: The MDRX comes with a ventilated 75% cylinder from the factory. Power values above assume a closed 100% cylinder. With the stock 75% cylinder, expect ~25% less energy.
Rapax Springs — RMS vs APS2
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
8. Outer Barrels
The MDRX offers two outer barrel lengths, both including the gas block assembly:
16” Standard Outer Barrel — 54.95€
The full-length outer barrel for the standard MDRX. Includes gas block. Accepts ~420mm inner barrels:
10.5” Micron Outer Barrel — 49.95€
The compact outer barrel for the MDRX Micron variant. Includes gas block. Accepts ~265mm inner barrels:
Muzzle Devices
Two muzzle device options for the MDRX:
- Raiden — Aggressive tactical flash hider design
- Ratchet — Multi-prong ratchet-style compensator
9. Body & Customization
The MDRX is fully customizable. Receivers, grips, stocks, carrilleras and handguards are all available individually, allowing you to build the exact colour combination and configuration you want.
Receivers (Polymer Body)
The main body of the MDRX. Available in FDE and Black:
Grips
Stocks & Carrilleras
The culata (buttstock) and carrilleras (cheek risers) allow ergonomic adjustment:
Handguards
Handguards are available for both the standard 16” and Micron configurations:
16” Handguards
Micron Handguards
▶ Alternative 16" handguards
10. Magazines & Caliber Conversion
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:
- Magazine adapter — Adapts the magwell to accept AR15 magazines
- 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
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
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:
- Hop-up bucking — The flat hop 80° bucking is already good, but a quality replacement can tighten groupings immediately
- Inner barrel (Morpheus 420mm) — The single biggest accuracy upgrade. Precision bore with consistent BB flight
- Cylinder (closed 100%) — Swap the ventilated 75% for the closed 100% to increase power output without changing the spring
- Spring — Adjust power to your field's rules. APS2 springs swap in seconds
- Outer barrel — Switch between 16” and 10.5” configurations to change the rifle's role
- 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.
13. MDRX Collections
Colecties MDRX
Elektronica MDRX
Bucking MDRX
MDRX Lopen
Kolf & Accessoires
Onderdelen & Kits
Zuigers & Cilinders
Hop-Up & Onderdelen
Lichaam & Onderdelen
Muzzle Devices & Accessoires
Veers
Grepen