The idea of simply converting a short weapon into a long one has a rich history and was originally related to the effort to better control burst-firing pistols. Even before World War I, several types of automatic pistols appeared, to which manufacturers attached an additional stock to improve combat handling. This stock also served as a holster.
A Century of History
The most famous type became the Mauser C96, produced since 1896 in calibers like 7.63mm, 9mm, or .45 ACP. A later model from 1932 enabled automatic fire and switched from the previous strip loading to 10 or 20 round magazines. Burst fire negatively affected accuracy, so the "holster stock" was more frequently used than in semi-automatic variants. The shooter attached it to the handle from behind and braced it against the shoulder, gaining a more stable grip and firmer support. Similarly, the Austrian 9mm Steyr M1912 initially emerged as a robust semi-automatic pistol. In 1915, a variant with an extended 16-round magazine appeared, allowing the shooter to attach a stock. Like the Mauser, the Steyr's stock gained popularity with the M1912/P-16 model, becoming the first pistol capable of burst fire. During the Cold War, designers didn't forget about such weapons, and similar solutions could be found in both the Western and Eastern blocs. In 1970, the German company Heckler & Koch introduced the 9mm VP70 (the world's first polymer-frame pistol) with an 18-round magazine. The weapon came with a plastic stock that also served as a holster, mounted on the back of the handle. A pin on the top projection engaged with a catch on the pistol frame, activating the three-round burst mode, which the shooter selected using a lever on the stock. In the 1970s, the Italian company Beretta also contributed with its model 93R, based on the famous 92 series. Designed for anti-terrorist units, it could fire three-round bursts in addition to single shots. The theoretical rate of 1100 rounds per minute made this feature, adopted by the Honduran army, somewhat difficult to control. Soviet designers had a similar idea in the 1950s, embodied in the Stechkin APS automatic pistol. It matched Western competitors and had a 20-round magazine for ample "feeding."
For Greater Certainty and Accuracy
Automatic pistols are not highly popular today, with semi-automatics taking the lead. So if there's no need to stabilize a short weapon for burst fire, what sense does it make to buy a conversion kit that turns it into something like a carbine or a "mini submachine gun" firing single shots? The answer is simple. The conversion gives you a similar ergonomic grip to a carbine, offering significantly greater control. More importantly, it provides a weapon with which you can hit targets more quickly and accurately, even at longer distances. Additionally, if the conversion kit allows for the mounting of an external sight, this effect is further enhanced. Legislative circumstances also favor buying a conversion kit for your pistol. For example, in Israel, where most top conversion kits come from, civilians are allowed to carry a visible weapon but are not permitted to own a submachine gun. Therefore, purchasing a conversion kit can be a good solution for pistol owners who desire a legally held long weapon. Moreover, the conversion kit itself is not considered a weapon or its main component, so it can be purchased without a firearms license, registration, or the need to apply for a purchase permit. For the same reason, you can safely store the kit in your car's trunk at a parking lot. One of the significant benefits is that even with "just" a pistol, the conversion allows you to practice handling more powerful arsenal. Besides practicing shooting, you can also train CQC (Close Quarters Combat) techniques with the improvised PDW, ideal for tactical team operations in confined spaces.
From Stock to Comprehensive Kit
There are various solutions differing mainly in the degree of transformation. The simplest involves add-on stocks, fundamentally similar to those described in the historical section. Today, they no longer serve as holsters; they resemble folding stocks of carbines in appearance and functionality and are fully adjustable according to the shooter's body proportions. Removable pistol stocks are no novelty on the Czech market, previously represented by products from the Israeli company Fobus. However, due to poor ergonomics, they didn't gain much traction. A middle ground is represented by Mech Tech CCU (Carbine Conversion Unit) conversions from the USA, imported to the Czech Republic about ten years ago. The main added value was a quality stainless steel barrel, but even the CCU didn't gain widespread use. They had to be registered, and the portfolio of compatible pistols was limited to Glock, Colt 1911, and Springfield XD. The price was prohibitively high, and instead of the whole pistol, only its frame was inserted into the conversion. Truly comprehensive and sophisticated conversions started appearing around 2009. Such kits nearly completely encase your weapon, revealing only the protruding grip. Unlike the CCU, no modification of the weapon is needed before installation, and quick-release systems allow easy switching between pistol and PDW in combat. Assembly is simple – after manually unlocking two pins, you insert the pistol into the rail, secure it with the rear pin, tighten the front pin, and you're done. Finally, you usually need to adjust the barrel extension to the correct position, depending on whether you use a larger weapon (like Glock 17) or a more compact model like Glock 19 – the extension must always align without a gap with the muzzle.
With Carbine Features
Modern sets are made from a combination of lightweight aluminum alloys and plastics, with metal parts typically being the most stressed parts, such as pins or barrel extensions. Generally, the higher the alloy content compared to polymer, the more durable the set is considered. While increasing the plastic content reduces costs, it also increases the play between the set's individual elements and between the conversion and the pistol. The most significant play appears at the top rear of the grip. Owners of pistols with polymer frames sometimes compensate for this play by applying two strokes of a hot glue gun or liquid metal to the degreased conversion – at the point where it grips the described part of the weapon – and inserting the weapon only after the strokes have slightly dried. Conversions typically include all the elements for grip and handling that you're accustomed to from rifles or carbines: telescopic multi-position stock, front grip, and sling attachment. Rails for mounting additional accessories are standard, and more sophisticated kits even include folding sights. Although the kit converts a short weapon into a long one, the assembly remains compact – for instance, the popular FAB Defense KPOS G2, with a length of 370mm (598mm with the stock extended), reaches dimensions similar to the legendary Mini-Uzi submachine gun (360mm/600mm). With a bit of skill, a pistol "dressed" in a conversion kit can still be suitable for concealed carry. At first glance, the price of conversion kits might seem like a disadvantage, with the best types approaching 15,000 CZK. However, when compared to semi-automatic PDWs, you'll find that conversions are more than worth it. For example, a semi-automatic Brügger & Thomet APC9 carbine from Switzerland, with accessories, costs around 75,000 CZK.
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