Description
Specna Arms SA-F04-RL FLEX™ BLDC™ Light Ops Stock / HAL ETU™ Gen. 2 - Olive
The Specna Arms SA-F04-RL FLEX™ BLDC™ Gen. 2 is a lightweight, high-performance M4-style AEG combining a factory-installed Dark Matter™ 27k brushless motor with programmable HAL™ ETU electronics and a reinforced Aether™ V2 gearbox. The Magnus™ TDC hop-up, Helium™ Flat Hop bucking and ESA™ quick spring-change system complete a package designed for players who want fast trigger response, extensive adjustment options and capable internal components without immediately investing in upgrades.
The FLEX™ BLDC™ series brings advanced motor technology and reinforced gearbox components into an accessible price category. The SA-F04-RL combines these features with a nylon fibre-reinforced polymer receiver, an M-LOK handguard and a compact adjustable Light Ops stock. Its olive finish provides a practical, understated appearance suitable for a wide range of airsoft loadouts.
Dark Matter™ 27k Brushless Motor - Fast and Efficient Performance
One of the most significant features of the FLEX™ BLDC™ series is the factory-installed Specna Arms Dark Matter™ High Speed 27k brushless motor.
Unlike conventional brushed AEG motors, a brushless motor does not rely on carbon brushes making mechanical contact with rotating components. This reduces brush wear and friction while improving electrical efficiency.
The Dark Matter™ motor provides responsive acceleration and strong torque, allowing the gearbox to complete its firing cycle quickly. This is particularly useful in semi-automatic operation, where motor response directly affects the delay between pulling the trigger and firing a BB.
The brushless design also eliminates the need to replace worn carbon brushes and reduces heat generated by mechanical brush contact. Combined with the programmable HAL™ electronics, it provides an excellent foundation for responsive operation and further performance adjustments.
HAL™ ETU Gen. 2 - Programmable Electronic Trigger System
The factory-installed HAL™ ETU uses magnetic Hall-effect sensors to detect trigger movement instead of conventional mechanical trigger contacts. Contactless detection reduces mechanical contact wear and allows the trigger activation point to be adjusted electronically.
The system also uses optical gear detection to monitor gearbox operation. Its programmable functions allow the player to customise trigger sensitivity, pre-cocking and firing modes without opening the gearbox or installing additional electronics.
Adjustable trigger sensitivity
Trigger sensitivity can be adjusted in five levels, from 20% to 100% of the trigger travel. A shorter activation distance provides a more responsive trigger feel, particularly useful for rapid semi-automatic shooting.
Six-level pre-cocking
Pre-cocking allows the piston to remain partially tensioned after a shot, reducing the amount of movement required before the next shot. This can significantly improve semi-automatic trigger response.
The six adjustment levels allow pre-cocking to be matched to the spring and gearbox configuration. Higher settings increase spring tension and mechanical load, so the feature should be adjusted with the complete build in mind.
Programmable firing modes
The HAL™ ETU allows the firing modes assigned to the SEMI and AUTO selector positions to be configured separately:
- AUTO position: Full Auto, Semi-Auto, 3-Round Burst or 5-Round Burst
- SEMI position: Semi-Auto, Binary Trigger, AUG Mode or Sniper Mode
- Binary Trigger: Fires once when the trigger is pulled and once when released
- AUG Mode: Semi-automatic fire with a partial trigger pull and automatic fire with a full pull
- Sniper Mode: Semi-automatic fire with a two-second delay between shots
Programming is performed directly through the trigger and fire selector, without requiring a computer or smartphone application.
Electronic protection and active brake compatibility
The HAL™ ETU includes low-battery warnings, electronic protection functions and an adjustable active brake feature.
Important: Specna Arms instructs users to disable the HAL™ active brake when using a brushless motor. Since this rifle is equipped with a Dark Matter™ BLDC motor, the active brake must remain disabled.
Reinforced Aether™ V2 Gearbox
The SA-F04-RL FLEX™ BLDC™ features the reinforced Specna Arms Aether™ Version 2 gearbox, designed for durability, convenient maintenance and future tuning.
The gearbox shell features additional reinforcement at critical stress points, particularly around the front of the gearbox. It also includes inspection openings for checking piston Angle of Engagement (AoE) and pre-cocking, along with practical adjustment and service features.
The gearbox components and features include:
- Reinforced Aether™ V2 gearbox shell
- Strengthened gearbox front section
- Pre-cocking and piston AoE inspection openings
- Anti-reversal latch release access
- Mechanical trigger adjustment
- Steel gears
- Polycarbonate piston with a full-length steel tooth rack
- Sealed aluminium nozzle
- 8 mm gearbox bushings
- ESA™ quick spring-change system
- Factory-installed HAL™ ETU electronic trigger system
The steel-toothed piston, reinforced gearbox shell and brushless motor provide a durable mechanical foundation for the rifle's responsive electronic operation. The inspection openings and service features also make the gearbox easier to maintain than a conventional basic gearbox.
Magnus™ TDC Hop-Up and Helium™ Flat Hop Bucking
The rifle features the Specna Arms Magnus™ TDC (Top Dead Center) rotary hop-up chamber. Its adjustment mechanism applies pressure vertically to the hop-up bucking, helping maintain consistent contact with the BB and making adjustments more repeatable.
The chamber is paired with the Helium™ Flat Hop bucking, designed to provide a broad and consistent contact surface. This helps generate stable backspin and is especially useful when using heavier BBs that require sufficient hop-up grip to maintain a predictable trajectory.
A 6.03 mm precision inner barrel, approximately 229 mm long, completes the hop-up and compression assembly.
These components provide a well-equipped accuracy system without requiring an immediate replacement of the hop-up chamber, bucking or inner barrel.
ESA™ Quick Spring Change System
The ESA™ quick spring-change system allows the main spring to be replaced without opening the gearbox, making it easier to adapt the rifle's power to different field limits.
The spring can be accessed through the rear of the receiver after removing the stock and buffer tube. The spring guide is then accessed using an appropriate tool, allowing the spring to be replaced before reassembly.
The rifle is supplied with an M120 spring installed at the factory and an additional M90 spring for lower-powered configurations.
The indicative muzzle energy figures for the two spring configurations are approximately 0.9 J and 1.6 J. Actual performance may vary between individual rifles, and muzzle energy should always be checked with a chronograph after changing springs.
When using the M90 spring, a suitable 7.4V battery is recommended to reduce the risk of malfunctions caused by excessive gearbox cycling speed.
Lightweight FLEX™ Construction and Light Ops Stock
The SA-F04-RL features a nylon fibre-reinforced polymer receiver designed to combine low weight with a rigid external construction. Important components, including the outer barrel, flash hider, charging handle and several control parts, are manufactured from metal.
The rifle features ambidextrous fire selector and magazine release controls, making operation convenient for both right- and left-handed players. A functional bolt catch holds the mock bolt open, providing convenient access to the hop-up adjustment wheel.
The lightweight Light Ops stock features six adjustment positions, rubberised cheek contact surfaces and a curved rubber butt pad. Its minimalist design reduces unnecessary weight while allowing the stock length to be adjusted to the player.
The polymer M-LOK handguard provides mounting positions for compatible accessories such as foregrips and weapon lights, while the full-length Picatinny top rail accommodates optics. Folding iron sights are also included.
A 14 mm CCW muzzle thread beneath the flash hider allows compatible tracer units, suppressor replicas and other muzzle devices to be installed.
Technical Specifications
- Manufacturer: Specna Arms
- Series: FLEX™ Gen. 2 BLDC™
- Model: SA-F04-RL Light Ops Stock / HAL ETU™ Gen. 2
- Product type: Electric airsoft rifle (AEG)
- Platform: M4 / AR15
- Calibre: 6 mm BB
- Receiver material: Nylon fibre-reinforced polymer
- Handguard: Polymer M-LOK
- Stock: Six-position adjustable Light Ops stock
- Gearbox: Reinforced Aether™ V2
- Electronic trigger unit: HAL™ ETU Gen. 2
- Trigger detection: Magnetic Hall-effect sensors
- Motor: Specna Arms Dark Matter™ High Speed 27k BLDC brushless
- Motor type: Long
- Trigger sensitivity: 5 adjustable levels
- Pre-cocking: 6 adjustable levels
- Active brake: Available in HAL™, must be disabled with the installed brushless motor
- Firing modes: Programmable Semi-Auto, Full-Auto, Burst, Binary, AUG and Sniper modes
- Gearbox internals: Steel gears, steel-toothed piston and sealed aluminium nozzle
- Bushings: 8 mm
- Quick spring change: ESA™
- Factory-installed spring: M120
- Additional spring: M90
- Indicative muzzle energy: approximately 0.9 J / 1.6 J, depending on spring
- Hop-up chamber: Adjustable Magnus™ TDC
- Hop-up bucking: Helium™ Flat Hop
- Inner barrel diameter: 6.03 mm
- Inner barrel length: approximately 229 mm
- Overall length: approximately 670-750 mm
- Weight: approximately 2125 g
- Magazine type: S-MAG mid-cap
- Magazine capacity: 125 rounds per magazine
- Battery connector: T-plug / Deans
- Battery compartment: Stock / buffer tube
- Recommended battery: Compatible 7.4V LiPo or Li-ion battery with Deans connector when using the M90 spring
- Muzzle thread: 14 mm CCW
- Blowback: No
- Colour: Olive
- Manufacturer product code: SPE-01-047995
- EAN: 5902543211910
Package Contents
- 1 × Specna Arms SA-F04-RL FLEX™ BLDC™ Light Ops Stock / HAL ETU™ Gen. 2 - Olive
- 2 × 125-round S-MAG mid-cap magazines
- 1 × BB speedloader
- 1 × M90 replacement spring
- 1 × Cleaning rod
- 1 × Small Tamiya-to-Deans battery adapter
- 1 × Hex key
- Folding iron sights, installed on the rifle
Battery and charger are not included and must be purchased separately.
HAL™ Trigger Activation Before First Use
The HAL™ trigger must be activated before the rifle is used for the first time. Follow these steps:
- Set the fire selector to SAFE.
- Connect the battery while the selector remains in SAFE.
- Wait approximately three seconds until the rifle emits a beep.
- Pull the trigger fully and hold it for approximately five seconds until another beep is heard.
The second beep confirms successful activation. Repeat the procedure if the HAL™ factory settings are restored.
Important: Keep the active brake disabled when using the factory-installed brushless motor.