One of the great advantages of 3D-printed designs is the ease with which they make it possible to go from the initial concept to prototype without exorbitant costs. This allows those with lots of ideas but perhaps not as much capital, to emerge with ingenious and well-conceived products. This is the case of SRU of Taiwan, founded in 2012 and active for more than a decade in the airsoft accessories sector, where it has stood out due to its futuristic and visionary approach to this very dynamic sector.
In 2023, SRU took the plunge and opened a Real Steel division with the aim of applying all its innovations to real firearms.
This division works with US law enforcement agencies, combining innovation and experience. SRU uses Mil-Spec processes to produce high-quality firearms kits and accessories in Taiwan, utilising advanced techniques such as CNC machining and injection molding.
Currently, the SRU Division's flagship products are the SRUNA-22 and SARB-15 chassis stocks, which allow the ubiquitous (at least in the USA) Ruger 10-22 semi-automatic rifle and AR-15 type Black Rifles to be converted into a bullpup, respectively.
Let us take a step backwards to take one forwards, and review the concept: bullpup rifles and carbines have the trigger group positioned in front of the magazine, allowing a reduced overall length while retaining a long barrel, thus not adversely affecting ballistic performance. This is a concept of purely military origin, taken into serious consideration after the Second World War when it became clear that the modern infantry was increasingly conceived as a mechanised force, and deployed via helicopters or armored vehicles. The bullpup configuration was ideal for mechanised troops: more manoeuvrability without compromising precision and power. Today, several armies around the world partially or fully adopt assault rifles in bullpup configuration: Austria with the Steyr AUG, France with the FAMAS, the UK with the SA-80, Croatia with the VHS-2, Israel with the IWI Tavor, and many others, which we discuss in detail in this article.
For civilian shooters – military considerations count for little – and semi-automatic rifles in bullpup configuration are something that many enthusiasts certainly desire . However, the market does not always offer civil versions of the assault rifles already mentioned, so conversion kits are welcome, allowing any "Black Rifle" to be transformed into a shorter, more handy and compact version. The same applies to the airsoft sector, and let's not forget that SRU conversions were initially made for this market.
The SARB-15 bullpup conversion kit in detail
As you may have guessed, the SARB-15 is a chassis stock that makes it possible to radically change the ergonomics of an AR-15 type rifle by actually moving the lower receiver to an intermediate position between the recoil pad and the pistol grip. This allows a drastic reduction in the overall length of the weapon and also a shift in the centre of gravity that makes it very easy to handle, especially in confined spaces. To give a practical example, once inserted into the SARB-15 chassis, a Black Rifle with an 18.5-inch (47 cm) barrel will be only 68.5 cm long instead of the approximately 90 cm of the traditional stock version. The SARB-15 conversion is compatible with upper receivers with a built-in recoil spring (e.g. Brownells-180, Palmetto State Armoury JAKL, Foxtrot Mike-15) or AR-15 type with a short-stroke bolt carrier installed. The conversion allows the user to retain the classic T-shaped charging handle of the AR-15 or use side charging handles, depending on user preference. At the rear of the stock, a polymer cheek piece protects the handle itself from impacts and acts as a deflector for ejected cartridge cases, keeping them away from the shooter's face.
The "real steel" (i.e. intended for real weapons) chassis is built from 6061-T6 aluminum and aerospace-grade fiberglass, while the cheaper airsoft version is made of polymer with steel parts. What they have in common is their full modularity, which means they can be fitted with stocks, grips, sights and any kind of accessory, such as the Jackl handguard, manufactured by SRU itself, compatible with barrels between 10.5 and 16 inches long, with side M-Lok slots and long enough to accommodate a silencer. For the time being, the stock is available in black, FDE, tan and white.
Another strength of the SRU kit lies in the trigger linkage design. The forward placement of the pistol grip and trigger in this type of kits requires a linkage that transfers the movement of the new trigger to the original one. This additional linkage is often a source of play and an overall deterioration in trigger quality. In contrast, the trigger linkage that comes with the SARB-15 has been carefully designed to maintain the cleanest possible release, regardless of whether it is single- or double-stage. Magazine release is via an oversized double lever located behind the magazine and on the right side of the receiver. As for the selector switch, the kit is compatible with any AR15 safety selector and grip, greatly increasing customisation options.
Let's talk about prices: the basic cost of the SARB-15 kitis $429.99 for the standard version. Depending on the weapon to be used with the kit, it may be necessary to spend a few tens of euros more for a dedicated buffer stop (for example, using a JACKL upper from Palmetto State Armoury). However, this is a reasonable amount of money, allowing you to completely change the design of your Black Rifle without too much effort and in a reversible way.
In conclusion, the SRU kit is an interesting exercise in style and we would sincerely like to try it out on a real steel gun to see how it performs in the field. For now, we invite you to watch the video and visit the Taiwanese company's website.
