Specna Arms SA-B01 ONE™ M4 AEG Rifle in Black

Specna Arms SA-B01 ONE™ M4 AEG Rifle in Black

The Specna Arms SA-B01 ONE™ M4 AEG in Black is a proper old-school M4A1-style airsoft rifle, combining the classic military carbine appearance with solid metal construction and some rather impressive internals. Made by Specna Arms as part of their popular ONE™ series, this full-metal airsoft gun offers the sort of reassuring weight and realistic handling that makes an M4 platform so enjoyable to use. There's no unnecessary furniture or overly complicated styling here. Just a traditional M4 assault rifle design, complete with a detachable carry handle, fixed front sight, adjustable stock and familiar polymer handguard. At approximately 3.5kg, it has a substantial feel without becoming awkward to shoulder, while the balanced construction makes it surprisingly comfortable to manoeuvre during a long day's skirmishing. For players who appreciate the traditional military look but still want modern AEG performance, the SA-B01 ticks plenty of boxes.

Starting at the front, the Specna Arms SA-B01 features a metal outer barrel with a traditional M4-style flash hider, mounted on a standard 14mm counter-clockwise (CCW) thread. This makes swapping the original flash hider for a compatible mock suppressor or alternative muzzle device straightforward. Moving backwards, you'll find the familiar triangular front sight assembly and classic two-piece M4 polymer handguard. The handguard separates in the same general fashion as its real-steel inspiration, providing access to the front battery compartment and wiring. It's a simple, proven arrangement that keeps the rifle looking authentic while offering enough space for a suitable battery. The original handguard can also be replaced with compatible aftermarket M4 furniture, giving you plenty of options if you fancy changing the appearance further down the line. Prefer a classic military carbine? Leave it exactly as it is. Sometimes the original look is hard to beat.

The receiver is where the SA-B01 ONE™ really starts to show its quality. Made predominantly from a zinc and aluminium alloy, with steel used for components such as pins, screws and sling attachment points, the construction feels reassuringly substantial. Specna Arms has also paid attention to the external finish, using surface treatments designed to improve resistance to corrosion and everyday wear. The receiver features realistic markings, including a distinctive US Navy insignia on the magazine well, giving the rifle a convincing military-inspired appearance. Up top sits the traditional detachable carry handle with integrated rear iron sight, mounted onto a standard 20mm Picatinny-style RIS rail. Remove the carry handle and you've got a flat-top receiver ready for a red dot sight, holographic optic or compatible scope mount. It's a particularly useful arrangement because you can switch between the classic M4A1 appearance and a more modern optic-equipped setup without making permanent modifications.

Moving towards the rear, the Specna Arms SA-B01 features a metal buffer tube, steel sling attachment plate and adjustable SF-style polymer stock. The collapsible stock allows you to alter the rifle's overall length from approximately 800mm to 880mm, making it easier to find a comfortable shooting position when wearing different equipment or thicker clothing. The textured butt pad helps keep the stock securely positioned against your shoulder, while the polymer pistol grip provides a familiar M4 handling experience. There's also a rear sling attachment point suitable for compatible single-point sling setups, particularly handy when transitioning between your primary airsoft rifle and a secondary during a game. The overall balance is worth mentioning too. Despite the metal construction and 3500g weight, the SA-B01 sits comfortably in the hands, with the adjustable stock helping you bring the sights naturally into position. It feels like a proper service-style carbine rather than a lightweight plastic imitation.

Inside the receiver sits a reinforced Version 2 gearbox, and this is where the Specna Arms ONE™ series earns much of its reputation. The upgraded internal configuration includes reinforced steel gears, 8mm ball bearings, a steel spring guide, lightweight polymer piston, sealed aluminium piston head, metal cylinder head and metal air-seal nozzle. These components work together to provide dependable mechanical operation and consistent air compression. The gearbox also features low-resistance silver wiring and is designed to work with suitable NiMH, LiPo and LiFe batteries. A 7.4V LiPo battery with a small Tamiya connector is a sensible choice, particularly when running the lower-powered spring. There's no factory MOSFET or electronic trigger unit fitted, so the SA-B01 retains a traditional mechanical AEG trigger arrangement. For players who enjoy maintaining and upgrading their own rifles, the familiar Version 2 gearbox layout also provides a well-established platform with plenty of compatible aftermarket components.

One of the most useful features of this Specna Arms M4 AEG is the Enter & Convert™ quick spring change system. This allows the main spring to be replaced without completely dismantling the gearbox, although the gearbox must first be removed from the receiver to access the system. The standard spring produces a quoted muzzle velocity of approximately 410 FPS, while the additional M90 spring included in the box can reduce output to around 310 FPS, depending on the rifle's individual setup and testing conditions. That's a particularly useful feature for players who visit different airsoft sites with different power limits. Bear in mind that the standard 410 FPS configuration may exceed the limits permitted for automatic electric rifles at many UK skirmish sites, so fitting the lower-powered spring and checking the rifle with a chronograph before playing is important. When using the M90 spring, Specna Arms recommends a 7.4V battery to help avoid potential operating issues. Always check your site's FPS and joule limits before heading into a game.

Accuracy and BB consistency are handled by a rotary-style adjustable hop-up unit paired with a 350mm inner barrel. The hop-up applies controlled backspin to the BB, helping it maintain a flatter flight path and improving usable range when correctly adjusted. Rotary adjustment is particularly welcome because it allows small, repeatable changes when setting the rifle up for your chosen BB weight. The SA-B01 also features a functional bolt catch mechanism, adding another satisfying touch of realism when accessing the hop-up adjustment area. Both semi-automatic and fully automatic firing modes are available, giving you the flexibility to take controlled individual shots or use short bursts when site rules permit. Feeding comes courtesy of the included 300-round steel high-capacity magazine, which provides a generous ammunition supply for general skirmishing. The rifle is also designed around the widely used M4 AEG magazine format, with compatibility reported across several aftermarket manufacturers, although individual magazine fit and feeding performance can vary.

Out on the airsoft field, the appeal of this rifle is easy to understand. The traditional M4 layout feels familiar, the metal receiver adds a satisfying sense of solidity, and the adjustable stock makes it easy to get comfortable behind the sights. The detachable carry handle is a lovely touch for anyone who enjoys classic military-inspired loadouts, while the hidden receiver rail means you can fit a modern optic whenever you fancy a change. The combination of a reinforced gearbox, adjustable hop-up and quick spring change system also makes the SA-B01 a practical starting point for future upgrades. It's particularly appealing to players who want a dependable full-metal airsoft AEG without jumping straight into complicated electronic systems or heavily customised externals. Just remember that its realistic weight is something to consider if you're accustomed to lighter polymer rifles, especially during longer games.

Overall, the Specna Arms SA-B01 ONE™ M4 AEG is a great choice for airsoft players looking for a traditional M4A1-style assault rifle replica with durable construction, sensible mechanical features and plenty of customisation potential. Its combination of metal externals, reinforced Version 2 gearbox, Enter & Convert™ spring system and standard M4-compatible furniture gives it a strong foundation for both regular skirmishing and future modifications. The included M90 spring adds welcome flexibility for UK site power limits, while the 300-round magazine gets you started without immediately needing additional magazines. Battery and charger are not included, so you'll need to select suitable power equipment separately. For anyone who likes their airsoft rifles with a bit of weight, a classic silhouette and internals that can be maintained and upgraded, the SA-B01 ONE™ is well worth considering.

Highlights

• Specna Arms ONE™ series M4A1-style electric airsoft rifle in Black
• Full-metal zinc and aluminium alloy receiver with steel reinforcement components
• Classic detachable M4 carry handle with integrated rear iron sight
• 20mm Picatinny-style upper receiver rail for compatible optics and accessories
• Traditional two-piece polymer M4 handguard with front battery storage
• Adjustable SF-style polymer stock with metal buffer tube and sling attachment plate
• Reinforced Version 2 gearbox with upgraded steel gears and 8mm ball bearings
• Enter & Convert™ quick spring change system for easier power adjustment
• Approximately 410 FPS with standard spring and 310 FPS with included M90 spring
• Rotary adjustable hop-up unit for improved BB flight consistency and accuracy
• 350mm inner barrel and 14mm CCW threaded outer barrel
• Semi-automatic and fully automatic firing modes
• Functional bolt catch mechanism for added realism
• Low-resistance silver wiring with small Tamiya battery connector
• Compatible with suitable NiMH, LiPo and LiFe batteries
• Includes a 300-round steel high-capacity M4 AEG magazine
• Compatible with a wide range of aftermarket M4-style external accessories
• Great platform for classic military loadouts, regular skirmishing and future upgrades

What's Included

• Specna Arms SA-B01 ONE™ M4 AEG Airsoft Rifle - Black
• 300-round steel high-capacity M4 AEG magazine
• Detachable carry handle with integrated rear iron sight and fixed front sight assembly
• Additional M90 main spring for lower-powered operation
• Battery and charger are not included

Technical Specifications

• Manufacturer: Specna Arms
• Product Name: SA-B01 ONE™ M4 AEG
• Product Code: SPE-01-004032
• Series: Specna Arms ONE™
• Platform: M4A1-style Airsoft Assault Rifle
• Power Source: Electric (AEG)
• Colour: Black
• Receiver Material: Zinc and Aluminium Alloy
• Additional Metal Components: Steel pins, screws and sling attachment points
• Stock, Pistol Grip and Handguard Material: