Specna Arms SA-B03 ONE™ SR-16 Carbine AEG; Kestrel Basic ETU

For those in search of an M4/AR-15 with a slightly longer barrel for more effective long-range engagements without taking too long to stay mobile; the SA-B03 SR-16 is where it's at! This AEG is based on the real steel SR-16 rifle, an enhanced M4/AR-15 variant built by a well-known high-end AR manufacturer in the US, designed as a perfect balance between assault rifle agility and marksman rifle accuracy.

The Specna Arms SA-B03 is a member of Specna's ONE™ range, the original Specna Arms M4/AR-15 platform sports the Enter & Convert™ quick change spring system which allows for easy power tuning without the need to split the gearbox shell and have to mess with gears. This not only makes power tuning more accessible for those of us with limited tech skills but also allows for a relatively easy conversion to the DMR role thanks to the ONE™  series internals which are designed to effectively handle up to M130 springs. Get this locked to semi-automatic and with a bit of HOP-up tuning and a new spring you are in DMR territory!

Starting up front we can find the KAC style birdcage flash hider, following the recognisable M4/AR-15 muzzle device style but with some more interesting geometry on the ports, linear grooves on the filled-out section and a cutout at the bottom front, designed to interface with KAC's QD suppressor. This device can easily removed and replaced with a tracer, suppressor or alternative flash hider thanks to the 14mm CCW male threading underneath, we think the device included with the platform looks different enough to stand out under close observation without losing the discrete, "means business" looks of the SR-16 rifle.

Following the alloy outer barrel rearwards we come to the KAC style low profile gas block which is positioned just ahead of the handguards in what is known as the "mid-length" gas block position. Mounted between the gas block and the receiver we can also see the dummy gas tube; a silver aluminium rod which is visible through the weight-reducing vents on the handguard, identical to the real rifle. The mid-length gas tube position improves the reliability of the real SR-16 and is one of the most notable areas in that it outdoes a standard military-issued M4, but for Airsoft purposes this just completes the SR-16 look and separates it visibly from more conventional M4 platforms.

The handguard is a near-perfect replica of the real KAC URX2, the handguard used on the real SR-16 to add additional rail space and facilitate modern shooting stances. The handguard is equipped with 20mm Picatinny rails at the 3, 6, 9 and 12 o'clock positions and also has QD sling sockets on either side; both at the front of the handguard and at the base, where it meets the receiver. The lower section of the handguard can also be removed to install a barrel-mounted M203 grenade launcher by removing the screws on each side, giving you the option of going "full Rambo" with the SR-16.

By modern standards, the URX2 handguard is an ageing design but it has more than its fair share of advantages built right in. As mentioned, the military-style configuration allows for mounting a grenade launcher; something very few modern M-LOK and KeyMod rails allow for. The "quad rail" configuration means you have all the space in the world for accessories without being limited to M-LOK or KeyMod rail sections when you need to mount something like a laser which needs to be zeroed to be useful.

The front sight is also built into the handguard rail itself and is retained by a button on the left side, keeping things low profile and light while still giving you a reliable aiming device without taking up any front rail space. The QD sling sockets are the icing on the cake, allowing for a quickly removable sling setup which can easily be reconfigured on the fly. The URX2 also looks positively deadly in our opinion, its dynamic swept-back front end gives the SR-16 the vibe of a lance just waiting to be pointed in the right direction!

The bolt release catch is functional on the SA-B03 ONE™, allowing you to pull the charging handle (located at the top rear of the receiver) and lock the mock bolt carrier back to reveal the rotary adjuster of the HOP-up unit. The rotary HOP-up unit design is the latest for the M4/AR-15 platform and allows for finer increments of adjustment than the legacy gear HOP-up unit as well as more effectively holding its setting under the vibrations of full auto fire.

Adjusting the HOP-up allows you to tune the SA-B03 ONE™ for your chosen weight of ammo and extend your range by applying backspin, a prerequisite of any Airsoft AEG which is intended for skirmishing. With your HOP-up adjustment complete, you can hit the "ping pong paddle" aka bolt catch on the centre left of the receiver and send the chrome-coloured mock bolt home with a satisfying metal-on-metal "clank".

Furniture-wise, the SA-B03 is equipped with an "A2" finger-ridged pistol grip and an M4/AR-15 Crane stock at the rear. The A2 grip is the original grip used on the M16A2 and M4A1 rifles and is known to be a comfortable grip for a variety of different hand sizes, though the grip can be swapped out for M4/AR-15 AEG aftermarket pistol grips if you have a preferred grip style and the technical expertise necessary. The trigger guard is the standard flat M4 type, keeping the trigger protected from accidental discharges and also allowing the guard to be opened up for use with thick winter gloves by pushing in the spring-loaded detent on the right side of the trigger guard at the front and folding the trigger guard back towards the grip. This isn't ideal for safety but may be essential when the frost sets in!

At the rear of the receiver, we are treated to a steel CQD style sling plate which allows single-point slings to be mounted on either side of the rifle and can also be paired with the QD sling sockets up front to mount a two-point sling. Being made from steel, this sling point is guaranteed to provide the strength necessary to support the SA-B03 and any accessories you have mounted, just make sure your sling is up to the task!

The sling plate is held on by a steel castle nut which also functions to keep the buffer tube firmly. The battery compartment of the SA-B03 is located inside the Crane stock and can be accessed by removing the butt plate. To do this, simply squeeze the two tabs at the toe of the stock together and push them through the stock to release the butt plate. 

After this, the battery plug which seals the two battery compartments will need to be pulled out which will reveal a mini-Tamiya battery connector inside. We recommend a 7.4v 2600mAh 25C LiPo Crane Stock Battery for the SA-B03, though you can use an M4/AR-15 buffer tube style 7.4V LiPo instead, however, if you choose to do so, you will potentially not be able to collapse the stock all the way with a buffer tube battery installed.

On the inside, the SA-B03 follows the usual Specna Arms ONE™ system format, sporting a plethora of pre-upgraded components with an emphasis on reduced mechanical stress and minimising things to go wrong. The gearbox is a version 2 with an alloy shell fitted with reinforced steel gears running on 8mm bushings, an aluminium piston head and cylinder head, a steel ball-bearing spring guide and an aluminium nozzle to top it off.

The highlight of this refined version of the original SA-B03 ONE™ is its Kestrel Basic ETU/MOSFET, offering 6 levels of adjustable pre-cocking, options for 3 round burst and binary trigger along with low battery warning, cycle completion, active braking and low/high voltage cutoff. This means you can crank up the trigger response for super fast double taps or run the SR-16 with SAFE-SEMI-3RND BURST fire controls. Also inside is a 6.03mm tightbore inner barrel and rotary HOP-up unit, giving you superb accuracy potential and the latest HOP-up design for M4/AR-15 platforms.

The Enter & Convert™ spring change system requires the gearbox to be removed from the receiver but doesn't require the gearbox itself to be opened, saving you hassle when it comes to power tuning. The ONE™ series was designed to run M130 springs, so there is little chance of failure from regular use with the M90 spring initially installed to meet UK legal requirements. This also means there is not much extra effort required if you decide to go full DMR build with the SA-B03; simply lock it to semi-auto only and drop in your choice of spring and you're ready for skirmishing! 

So, if you are looking for an M4/AR-15 with a base long range and the potential to go even further into the DMR realm, the SA-B03 would be a fine choice. Being slightly longer than the average assault rifle but still shorter than a full-length rifle or SPR, the Specna Arms SA-B03 ONE™ SR-16 Carbine AEG; Kestrel Basic ETU styling presents a unique opportunity for engaging at longer ranges without hindering your mobility with an overly heavy or long rifle!

Features

• Full metal construction
• 16-inch outer barrel - The perfect length for a DMR build
• 14mm CCW Male threaded outer barrel - Ready for a tracer or suppressor
• URX2 Style quad rail handguard - Integrated front flip sight, lower can be removed to mount M203
• Integrated front flip-up sight - Hidden in the front of the URX2, saves rail space
• Numbered rail slots - Keep track of where you place your accessories when switching platforms
• QD Sling sockets on either side of the handguard - QD sling swivel ready
• Steel CQD style sling plate - Ready for single-point slings or pair it with the QD sockets at the front
• Rotary adjustable HOP-up unit - The most recent design for the M4/AR-15 platform
• 6-Position M4/AR-15 buffer tube - Allows stock adjustment to suit your body type and loadout
• M4/AR-15 Crane stock - Sloped cheek rest for comfort, sling slots built-in
• Rear wired - Deans battery connector inside the Crane stock
• Recommended battery - 7.4v 2600mAh 25C LiPo Crane Stock Battery
• Finger ridged "A2" pistol grip - Textured sides and rear for extra grip
• Version 2 gearbox:
  • Enter & Convert™ quick change spring system
  • Steel spring guide
  • 8mm Ball bearing bushings
  • 18:1 Ratio steel gear set
• Kestrel Basic MOSFET/ETU functions:
  • Binary Trigger
  • 3-Round burst
  • Active braking
  • Low/high voltage cutoff
  • Low battery warning
• Kestrel Basic MOSFET/ETU programming instructions are available here
• Compatible with M4/AR-15 AEG magazines - Plenty of spares and styles available!

Package Includes

• Specna Arms SA-B03 ONE™ SR-16 Carbine AEG; Kestrel Basic ETU
• 300rnd High-capacity magazine
• Specna Arms stickers