Silverback MDR-X HPA Conversion Kit

The MDRX HPA Conversion Kit allows you to convert your MDRX AEG into an electro-pneumatic HPA replica.

Based on a simple and extremely robust open-bolt HPA architecture, the MDRX HPA engine was designed to provide outstanding reliability, exceptionally consistent BB feeding, a wide power adjustment range and a very high rate of fire, while keeping maintenance requirements to a minimum.

The kit includes:

• MDRX HPA engine
• 2 mounting screws (M4 × 12 ISO 14581)
• HPA line with male PCP fitting
• FCU and wiring harness
• MDRX HPA hop-up chamber
• Silverback SRS/TAC-41 80° hop-up bucking
• Pre-installed 6-hole / Full Flow nozzle and spare 2-hole nozzle

HPA Engine

The MDRX HPA system is based on a 3-way/2-position 3V110-06 NCF industrial solenoid valve powered by 12 V DC. This industrial solenoid valve architecture ensures extremely high reliability, low maintenance requirements and an affordable price.

In this HPA engine, the airflow used to propel the BB does not pass directly through the solenoid valve. The solenoid valve only controls the movement of the nozzle:

When energised, air pressure pushes the nozzle forward and chambers a BB.

Once the nozzle is in position, air flows directly through the port or ports machined into the nozzle to propel the BB.

The nozzle movement is entirely pressure-driven, with no return spring and only one moving part.

The entire pneumatic assembly consists of only 4 parts and 5 sealing O-rings, including just 3 dynamic FKM/Viton O-rings. The nozzle is made from POM to reduce friction and moving mass while preventing damage to the BBs.

When the solenoid valve is de-energised, the air used to actuate the nozzle is vented directly into the replica’s lower receiver through the solenoid valve’s exhaust port. Since the propulsion airflow completely bypasses the solenoid valve, its flow rate does not limit the maximum power output that can be achieved.

Pressure Range and Performance

The system operates between 4 and 8 bar (58 to 116 PSI). However, the best accuracy and shot-to-shot consistency are generally achieved at lower pressures, typically between 4.5 and 6.5 bar (65 to 94 PSI).

For this reason, Silverback recommends:

• Using the least restrictive nozzle possible
• Using heavy BBs whenever possible
• Taking advantage of the system’s strong Joule Creep effect when using heavy BBs

The MDRX HPA is capable of achieving:

• Up to 40 rounds per second without difficulty
• Up to 50 rounds per second with advanced tuning and a higher operating pressure

Nozzle Configurations

Three nozzle configurations are available:

• 1-hole nozzle: optimised for setups below 1 joule.
• 2-hole nozzle: recommended for setups between 1 and 1.4 joules.
• 6-hole / Full Flow nozzle: recommended for setups above 1.4 joules.

HPA-Specific Hop-Up System

The MDRX HPA uses a dedicated hop-up chamber specifically developed for this pneumatic system. An integrated feeding guide directs the BBs straight towards the front face of the nozzle, ensuring exceptionally reliable feeding, perfect BB alignment and the complete elimination of double-feeds and misfeeds.

The HPA engine and hop-up chamber are designed to automatically align with each other, ensuring maximum consistency.

The chamber accepts standard AEG-spec hop-up buckings. However, Silverback strongly recommends using SRS/TAC-41-type buckings to achieve the best possible air seal.

All MDRX HPA kits come factory-fitted with a Silverback SRS 80° hop-up bucking. A harder bucking improves stability and shot-to-shot consistency with this HPA architecture.

Air and Battery Consumption

Under optimal conditions, the system provides approximately 2,000 to 2,500 shots from a 0.8 L / 48 cu in air tank filled to 207 bar / 3,000 PSI.

The system requires an 11.1 V stick-type LiPo battery. A 1,200 mAh battery will generally provide enough runtime to empty several air tanks.

Electronic Control Unit (FCU)

Developed in collaboration with T238, the FCU allows the following settings to be adjusted:

• Fire modes (safe / semi-automatic / 3- to 5-round burst / full-auto / binary)
• Solenoid valve opening time, or “dwell” (in 0.5 ms increments)
• Rate of fire (from 12 to 50 rounds per second)
• Delay between shots in DMR mode (from 0.5 to 5 seconds or disabled)
• Battery protection level (from 3.3 to 3.0 V per cell or disabled)
• Sleep timer (from 1 to 10 hours or disabled)

Additional FCU functions include current program readout, a lifetime shot counter, a daily shot counter, factory settings restoration and daily shot counter reset.