The M4 is a compact automatic rifle developed in the United States based on the popular M16 assault rifle. Designed to meet the need for a lighter, shorter version of the M16 suited for close-quarters and urban combat.
In the 1960s, the M16, developed by Armalite and adopted by the US Army, laid the foundation for the M4. The first prototypes of the M4 appeared in the 1980s with a shorter barrel and telescopic stock, improving handling in confined spaces.
In the 1990s, the M4 was officially adopted by the US armed forces as the standard carbine, replacing older models such as the M3 and M9. The M4’s ability to fire in single shots or bursts makes it a versatile weapon.
The M4 quickly became popular among soldiers due to its light weight, compactness, and reliability. It was widely used in conflicts such as the Iraq and Afghanistan wars, becoming an iconic weapon of the modern US military.
In addition to the standard model, there are many variants of the M4 equipped with different accessories and upgrades to meet the specific needs of military units.
The AEG assault rifle M4 in the basic FLEX™ series by Specna Arms emphasizes a lightweight nylon body combined with excellent construction and fit. The fiberglass-reinforced body offers greater durability than standard metal alloys, appreciated by beginners and advanced players alike who favor the lightweight nature for speedsoft action. This material is also found in the CZ Scorpion Evo and MP7.
The FLEX series is essentially a counterpart to the CORE series, with FLEX featuring a nylon handguard compared to the CNC metal handguard in CORE. Internal components are identical to CORE.
What does the Specna Arms M4 Carbine RL M-LOK (SA-F05-RL FLEX™ HAL ETU™) offer?
Internal Components
The M4 Carbine RL M-LOK (SA-F05-RL FLEX™ HAL ETU™) is equipped with an HAL ETU™ electronic processor unit for exceptional performance, bringing Specna Arms into the upper echelon of brands offering advanced features in their base models.
HAL is named for its use of Hall effect technology, which enables sensitive trigger response detection.
The M4 comes standard with a 6.03 mm precision barrel for improved accuracy and an adjustable hop-up chamber with a quality rubber.
It also includes the increasingly common ESA quick spring change system, allowing easy spring replacement through the stock tube without removing the gearbox.
The reinforced gearbox can handle springs up to M120 as specified by Specna Arms.
HAL ETU™ functions include:
- Trigger response detection via magnetic sensors and Hall effect
- Active brake
- Binary trigger (fires on press and release)
- Adjustable trigger sensitivity (5 levels from 20% to 100%)
- Adjustable piston pre-cocking (6 levels)
- Programmable semi-auto modes (semi, binary, AUG, sniper delay)
- Programmable auto modes (auto, semi, 3-round burst, 5-round burst)
- Simple programming via trigger
- Low battery warning
- Brushless motor compatibility (e.g., Specna Arms Dark Matter or Warhead)
Important instructions for weapon activation
To start shooting, the HAL ETU unit must be activated by following this procedure exactly, otherwise the weapon will not respond to the connected battery:
- Switch the selector to Safe.
- Connect the battery and wait for 3 seconds until a beep sounds.
- Pull the trigger and hold it for 5 seconds until another beep sounds.
- The weapon is now ready for use.
External Components
The Specna Arms M4 Carbine RL M-LOK (SA-F05-RL FLEX™ HAL ETU™) has a high-quality nylon body with a matte finish and realistic appearance. As part of the RL SAAS (Specna Arms Accessory System) line, it has a distinctive, aggressive look that differs from classic AR15 receivers. Fiberglass-reinforced, it is highly durable yet lightweight.
The metal outer barrel and steel screws, ejection port, and pins ensure reliability.
Ergonomic AR15 design and modern construction offer comfortable handling and ease of use. This rifle simply feels right!
The nylon M-LOK handguard on the M4 supports accessories such as grips, AN/PEQ boxes, flashlights, etc.
Equipped with an adjustable Crane stock, the rifle is ready for diverse scenarios, accommodating Buffer Stick, Nunchuck, or Crane type batteries.
Overall, it combines lightweight design and excellent internal components at an attractive price.
FLEX series plastic parts include:
- Receiver
- Stock tube
- Handguard
- Pistol grip, stock, and sights, as in the Edge series
Metal parts include:
- Outer barrel with 14 mm suppressor thread
- Flash hider
- Handguard nut
- Charging handle for hop-up access
- Screws, pins, and small receiver components, made of steel
Key Features
- High-quality nylon body reinforced with polymer fibers
- Programmable HAL ETU™ unit with T-DEAN connector in the stock
- Crane stock for multi-part battery placement
- QD ESA quick-change spring V2 gearbox
- Reinforced polymer piston with all steel teeth
- Polymer nozzle
- Polymer cylinder head with sealing and metal nozzle base
- Polymer piston head with sealing
- 8mm metal slide bearings
- Standard ratio gear set 18:1
- Polymer rotary hop-up chamber
- 6.03 mm precision barrel
Package Contents
- Specna Arms AEG rifle
- Hi-Cap S-MAG magazine for 380 BBs
- Folding sights
- Spare weaker spring (M90) for CQB
- Specna Arms stickers
- User manual
