Description
Compact Power, PRIME Performance: Specna Arms SA-P21 PRIME M4/AR-15 AEG – High-Torque Motor Version
Bring advanced electronics, a reinforced gearbox and a compact modern design to your airsoft loadout with the Specna Arms SA-P21 PRIME SA-P21 M4/AR-15 AEG. This High-Torque Motor version combines Specna Arms’ upgraded AETHER V2 gearbox with a 22TPA high-torque motor and programmable HAL electronic trigger unit, creating a feature-packed platform for players who want more control over their rifle’s performance.
Featuring a full-metal receiver, compact 5-inch CNC aluminium M-LOK handguard and adjustable crane-style stock, the SA-P21 offers a practical balance of compact handling and familiar M4 ergonomics. The Nano Coating finish, modern furniture and integrated rail options give you plenty of scope to configure the rifle around your preferred playing style.
Inside, the reinforced gearbox, CNC steel gears, adjustable Magnus TDC hop-up and ESA2 quick-change spring system provide a strong technical foundation. With two 125-round S-MAG mid-cap magazines included, the SA-P21 is ready to become the centrepiece of a modern M4 setup.
High-Torque Motor and Reinforced AETHER V2 Gearbox
This particular SA-P21 PRIME configuration uses a 22TPA high-torque brushed motor with neodymium magnets. It is paired with Specna Arms’ reinforced AETHER V2 gearbox, featuring CNC-machined 16:1 steel gears running on 8mm J-CAGE bearings.
The internal assembly includes a reinforced polymer piston with a full steel tooth rack, reinforced tappet plate and CNC aluminium piston head, cylinder head and nozzle. The steel cylinder and quick-change spring guide complete an upgraded drivetrain designed for regular skirmishing.
It is worth noting that this is the High-Torque Motor version, not the separate PRIME configuration fitted with the Dark Matter brushless motor.
HAL Programmable Electronic Trigger Unit
The integrated HAL Electronic Trigger Unit (ETU) uses magnetic sensors and Hall-effect detection to monitor trigger input. It offers a range of programmable settings, allowing you to tailor the rifle’s trigger response and firing behaviour without replacing the electronic system.
Available functions include:
- Binary Trigger: Fires on both trigger pull and release.
- Programmable Burst: Configure three-round or five-round burst modes.
- Semi-Automatic Only: Configure the rifle for semi-auto operation.
- AUG-Style Trigger: Two-stage trigger behaviour.
- Sniper Delay Mode: An alternative firing configuration.
- Adjustable Pre-Cocking: Six levels to tailor trigger response.
- Trigger Sensitivity: Five adjustment levels from 20% to 100%.
- Active Braking: Electronic braking function.
- Low-Battery Alarm: Alerts you when battery voltage is running low.
HAL settings are adjusted through the trigger using the manufacturer’s programming instructions. Always check your chosen site’s rules before using programmable firing modes.
Magnus TDC Hop-Up and Precision Inner Barrel
The SA-P21 is fitted with Specna Arms’ Magnus TDC rotary hop-up chamber, paired with a Helium Flat Hop bucking and a 6.02mm stainless steel tightbore inner barrel.
The top-down-centre adjustment system provides a convenient way to fine-tune hop-up pressure. Correctly setting the hop-up for your chosen BB weight helps achieve a consistent flight path and makes the most of the rifle’s setup.
Compact M-LOK Design and Full-Metal Receiver
The SA-P21 features a full-metal receiver with a Nano Coating finish and a compact 5-inch CNC aluminium M-LOK handguard. A full-length 20mm Picatinny rail runs along the top, while removable and repositionable rail sections provide additional mounting options on the sides.
The adjustable six-position crane-style stock allows you to find a comfortable length of pull, while the textured pistol grip and foregrip provide a secure hold. At the front, the birdcage flash hider conceals a 14mm CCW threaded barrel, allowing compatible muzzle accessories to be fitted.
ESA2 Quick-Change Spring System
Specna Arms’ ESA2 quick-change spring system makes it easier to adjust the rifle’s output without removing the gearbox from the receiver. This is particularly useful when configuring the rifle for different site limits or playing environments.
Always check your site’s power limits and chronograph the rifle in its intended configuration before use. Any spring changes should be carried out correctly and safely.
Battery Requirements – Please Read
RECOMMENDED BATTERY: 7.4V LiPo ONLY.
Specna Arms PRIME AEGs intended for the UK market can pre-engage when used with an 11.1V LiPo battery. Specna Arms’ supplier guidance recommends using a 7.4V LiPo battery for this version.
Faults arising from the use of an 11.1V LiPo battery may not be covered by the manufacturer’s 12-month warranty. The battery and charger are sold separately.
The battery compartment is located inside the buffer tube, accessed by removing the adjustable stock. The rifle uses a Deans/T-Connect battery connection. A Mini Tamiya-to-Deans adapter is included in the package.
Technical Specifications
| Specification | Details |
|---|---|
| Manufacturer | Specna Arms |
| Model | SA-P21 PRIME M4/AR-15 |
| Version | High-Torque Motor |
| Platform | M4 / AR-15 AEG |
| Power Source | Electric |
| Motor | 22TPA High-Torque Brushed Motor with Neodymium Magnets |
| Gearbox | Reinforced AETHER V2 |
| Gear Ratio | 16:1 CNC Steel Gears |
| Bearings | 8mm J-CAGE Bearings |
| ETU | HAL Programmable Electronic Trigger Unit |
| Hop-Up | Magnus TDC Rotary Hop-Up |
| Hop-Up Bucking | Helium Flat Hop |
| Inner Barrel | 175mm x 6.02mm Stainless Steel |
| Outer Barrel | 7 Inch |
| Muzzle Thread | 14mm CCW |
| Handguard | 5 Inch CNC Aluminium M-LOK |
| Receiver | Full Metal with Nano Coating Finish |
| Stock | Six-Position Adjustable Crane-Style Stock |
| Magazine Type | M4 / AR-15 AEG Mid-Cap |
| Magazine Capacity | Approximately 125 Rounds Each |
| Included Magazines | 2 x 125-Round S-MAG Mid-Caps |
| Battery Recommendation | 7.4V LiPo |
| Battery Connector | Deans / T-Connect |
| Approx. FPS | 330 FPS +/- 10% (using 0.20g BBs, supplier specification) |
| Approx. Weight | 2.2kg |
| Length | Approximately 62-71cm |
Recommended Add-On: Specna Arms S-MAG 125-Round Mid-Cap Magazine
Give Yourself More Magazine Capacity
The SA-P21 already comes supplied with two 125-round S-MAG mid-cap magazines. If you want additional magazines ready for your next skirmish, we recommend adding another Specna Arms S-MAG 125-Round Mid-Cap to your order.
Designed for M4/AR-15 AEG platforms, this is a great matching magazine option for the SA-P21 PRIME.
Shop the Specna Arms S-MAG 125-Round Mid-Cap Magazine at BR Airsoft
What’s Included?
- 1 x Specna Arms SA-P21 PRIME M4/AR-15 AEG – High-Torque Motor Version
- 2 x 125-Round S-MAG Mid-Cap Magazines
- 1 x Mini Tamiya-to-Deans Adapter
Battery and charger are not included and must be purchased separately.
UK Airsoft Use
The SA-P21 is supplied with a quick-change spring system, allowing its output to be configured for different site requirements. Always check your chosen site’s FPS or joule limits and have the rifle chronographed using the BB weight you intend to use.
Remember that UK airsoft site rules can vary, particularly around programmable firing modes. Make sure your HAL ETU settings comply with the rules of the venue you are attending.
As with other realistic imitation firearms, UK purchasing requirements apply. If you do not have an applicable defence under the Violent Crime Reduction Act 2006, ask BR Airsoft about an appropriate two-tone option before ordering.
The BR Airsoft Pro Take
The SA-P21 PRIME is an interesting option for players who want the advanced features of the PRIME range but prefer a conventional high-torque motor setup over a brushless configuration.
The combination of the reinforced AETHER gearbox, programmable HAL ETU and Magnus TDC hop-up gives you plenty to work with. The compact handguard also makes this a practical choice for players who prefer a shorter M4 platform, without sacrificing the familiar controls and adjustable stock of a traditional AR-style rifle.
With two 125-round magazines included, you have a good starting setup straight out of the box. We’d recommend adding an extra S-MAG magazine if you like to carry additional loaded magazines during a game.
Frequently Asked Questions
Q: Is this the brushless version of the SA-P21 PRIME?
A: No. This is the High-Torque Motor version, using a 22TPA brushed motor with neodymium magnets. It is different from the PRIME models equipped with the Dark Matter brushless motor.
Q: What battery does the SA-P21 use?
A: It uses a Deans/T-Connect battery connection and is recommended for use with a 7.4V LiPo battery. The battery and charger are sold separately.
Q: Can I use an 11.1V LiPo battery?
A: Specna Arms’ guidance for UK-market PRIME AEGs recommends using a 7.4V LiPo. Using an 11.1V battery can cause pre-engagement and may affect warranty cover.
Q: How many magazines are included?
A: Two 125-round S-MAG mid-cap magazines are included with the rifle.
Q: Will the BR Airsoft S-MAG 125-round magazine fit this rifle?
A: Yes. The BR Airsoft-listed Specna Arms S-MAG 125-round mid-cap is designed for M4/AR-15 AEG platforms and is a suitable additional magazine option for the SA-P21.
Q: Does the rifle have a programmable trigger?
A: Yes. The HAL ETU offers programmable firing modes, trigger sensitivity adjustment, pre-cocking, active braking and other features.
Q: Can I change the spring?
A: Yes. The ESA2 quick-change spring system allows spring changes without removing the gearbox from the receiver.
Q: Does it have a threaded barrel?
A: Yes. It has a 14mm CCW threaded outer barrel, allowing compatible muzzle accessories to be fitted.
Shop the Specna Arms SA-P21 PRIME at BR Airsoft
Combining a reinforced gearbox, high-torque motor, programmable electronics and compact M-LOK construction, the Specna Arms SA-P21 PRIME M4/AR-15 AEG is a feature-packed platform for players looking for a modern, configurable airsoft rifle.
Don’t forget to check out the compatible Specna Arms S-MAG 125-Round Mid-Cap Magazine as an additional purchase.
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