Compact Thunder: CZ-USA's 805 BREN S1 Pistol

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Compact Thunder: CZ-USA’s 805 BREN S1 Pistol
While the S1’s magazine well accepts AR-style magazines, CZ offers a kit to convert it for use with proprietary 805 BREN magazines.

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Compact Thunder: CZ-USA’s 805 BREN S1 Pistol
The aluminum receiver and matching bolt carrier are both serialized to ensure the correctly headspaced bolt stays with the rifle during assembly.

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Compact Thunder: CZ-USA’s 805 BREN S1 Pistol
The S1 pistol traces its roots to the CZ 805 BREN A2 battle rifle, which was designed as a modular platform that can accept different barrels, magazine wells and even chamberings.

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Compact Thunder: CZ-USA’s 805 BREN S1 Pistol
The CZ 805 Bren S1 Pistol, available in black or Flat Dark Earth (shown), is far shorter than AR-platform pistols and uses a gas piston system that runs cleaner and cooler while giving it a weight-forward balance.

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Compact Thunder: CZ-USA’s 805 BREN S1 Pistol
“… the S1 is a robust, reliable and very well made weapon with a smooth-functioning action and trigger, a high-quality finish and well-fitted parts.”

Pistol versions of semi-automatic rifles have become increasingly popular in recent years, and one of the more unusual ones is the CZ 805 BREN S1 Pistol that made its debut in the U.S. early last year. The S1 is a pistol version of the short-barreled, select-fire CZ 805 BREN A2 rifle that was introduced overseas in 2007.

Under The Hood

The S1 uses a short-stroke gas piston operating system. “Short-stroke” means the gas piston moves a distance shorter than the length of the cartridge. The stainless steel gas tube and gas block are mounted above the barrel and use a two-position regulator with settings for regular use and a wide-open port for extreme conditions. The gas settings are indicated by two different-sized dimples on the piston.

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The rotating bolt closely resembles the M16’s seven- lug design, and the S1 uses a reciprocating charging handle that can be mounted on either side of the receiver and also serves as a forward assist when encountering a partially chambered round. The action works very smoothly, underscoring the high quality of this pistol’s machining and construction.

Though the CZ design team originally used polymer for the 805 BREN receiver, a monolithic design that uses high-strength aluminum was introduced during development. The S1’s receiver is milled from a 7075-T6 forging and attaches to a polymer trigger housing with two pushpins. This aluminum-over-polymer approach is similar to that of the FN SCAR series. I think this setup is a better choice because the cost and weight advantages of using a polymer receiver are outweighed by an inevitable loss of zero that polymer-receiver rifles experience as they heat up during sustained fire.

The original 805 BREN used a proprietary magazine that rocks and locks with a paddle-style mag release like an AK-47’s. Luckily, the firearm’s design features a modular mag well, meaning guns coming to the U.S. are equipped to take AR-15 magazines. For those who want to use the CZ mags, a kit with a magazine well and five magazines will soon be available from CZ-USA for $150.

Though the receiver has an integral, full-length Picatinny rail on its top for mounting optics, the S1 comes with removable front and rear flip-up sights for quick targeting. Made from aluminum, the sights consist of a rear aperture and a protected post front. Adjusting the rear sight for windage is best done with a coin, while a tool or a cartridge tip can help you adjust the threaded front sight post for elevation. The rear sight has four apertures, ranging in size from ghost ring for CQB to small for precision sighting, that rotate into place.

The S1’s controls are roughly in the same convenient places as those on a typical AR, but the safety and bolt catch work differently. To me, having to put a weapon into the “fire” mode to clear the chamber when unloading is an oddity, yet the S1’s ambidextrous safety locks the bolt when activated.

The bolt catch is mounted on the left side, where you would find an AR’s, but while the AR’s locks and releases the bolt, the S1’s catch only locks the bolt rearward while depressing; the charging handle must be pulled rearward and released to chamber a round. The catch also has a fence surrounding its lower side that took some getting used to.

The magazine release buttons are ambidextrous, and a plastic shell deflector is mounted at the rear of the ejection port to protect the faces of left-handed shooters. The trigger has a very smooth travel of about 0.5 inches and a pull weight of 5.63 pounds according to my Lyman digital trigger pull gauge.

Like the BREN A2, the S1 has an 11-inch, cold-hammer-forged, medium-profile barrel capped with a two-chamber muzzle brake. The barrel has six-groove, 1-in-7-inch twist rifling. While current S1 models have 1/2×28 muzzle threading, the select-fire 805 BREN and earlier S1s had metric 14×1 LH threading. The barrel can be changed in the field using an Allen wrench to remove six screws—three on each side of the receiver. Evincing careful engineering, these screws use polymer sleeves to lessen the transmission of heat from the barrel to the receiver. Removing them allows the barrel and the attached Picatinny rail to be withdrawn. The original 805 BREN was designed with modularity in mind. The ability to swap to different chamberings like the 7.62x39mm or 6.8 SPC is there, though to date only 5.56mm NATO variants have been produced. Time will tell whether LE/military contracts or demand will justify more chamberings.

Field-stripping the S1 is easy and starts with clearing the weapon. Then remove two pushpins that secure the trigger assembly and separate it from the receiver. Push a spring-loaded plunger on the back plate on the rear of the receiver, then lift it up to allow the recoil spring and bolt carrier group to be removed. The bolt carrier (serialized to match the receiver) rides on full-length rails inside the receiver, a design that carries none of the carrier tilt problems associated with piston-driven AR-15s with conventional buffer tubes. The gas piston and operating rod are easily removed by depressing a spring detent to allow the piston to be rotated and removed.

Piston Power

Given its size—almost 23 inches long and weighing 6.7 pounds unloaded, as much as some AR-15 rifles—the S1 is a substantial piece of hardware. Since the S1 lacks an AR-pistol-type buffer tube that many shooters utilize to stabilize the firearm, each user needs to find a shooting grasp that works best.

Because the sight radius is much longer than on a conventional pistol, I tested the S1 for accuracy from a benchrest at 50 yards rather than the usual 25 yards prescribed for testing full-sized handguns. The S1 was accurate with the average group sizes with ball ammo measuring less than 3.5 inches using just the iron sights. Tighter groups would certainly be possible if a scope or holographic sight were added. Aiming was possible with all aperture sizes, but the smallest size was clearly better with a closer eye relief than a shooter would use on a pistol.

The S1 ran flawlessly with the four common factory loads I tested. Recoil was negligible given the S1’s weight and chambering, but like all short-stroke gas piston systems, the impulse is more disruptive than the direct-impingement AR because the operating rod slams against the bolt carrier.

Most shooters will wonder how much velocity is lost when using the S1’s short 11-inch barrel compared to a 16-inch rifle barrel. Testing this would require a longer barrel for this same platform, which was unavailable for my test. However, I chronographed the velocities for each test load from a 16-inch-barreled, direct-impingement AR-15 to get a comparison. The results showed that the S1’s 11-inch barrel gave up an average of 295, 323 and 328 fps for the Remington, Federal and Independence loads, respectively.

One concern I had was that the aluminum foregrip area, with its Picatinny-style bottom rail, is somewhat sharp and should be shielded with a rail cover.

Finally, the S1 can be slung from a swivel at the rear of the receiver using a neck sling, but the weight is apparent, so slinging it across the shoulders or using a single-point sling might be better.

Quality Build

As CZ puts it, the S1 has proven a popular short-barreled-rifle (SBR) candidate for customers wanting to convert it to an NFA firearm. I agree fully. Because of its size, weight and caliber, the S1, wearing a folding stock and other 922r parts, would be slick. (Note: Under current federal law and ATF policy attaching a stock to this pistol or attaching a device which is then used as a stock or intended to be used as a stock constitutes making an SBR, which requires registration with ATF and the payment of the applicable tax. Users of the CZ 805 BREN S1 Pistol bear the sole responsibility for ensuring their use of the firearm complies with all local, state and federal firearms laws.)

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But, as it stands, the S1 is a robust, reliable and very well made weapon with a smooth-functioning action and trigger, a high-quality finish and well-fitted parts.

For more information, visit cz-usa.com or call 800-955-4486.

Specifications