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CZ’s semi-auto 805 Bren S1 Carbine has been well received in the US, see how it stacks up to the Czech Army original

The U.S. consumer has often benefitted from military arms development that occurs in faraway places worldwide and that eventually produces civilian versions for U.S. markets.

One recent example is the Czech CZ 805 Bren that was developed in 2009 as a select-fire military rifle and debuted in the United States in 2015 in both LE/MIL and civilian variants. The 805 Bren was originally intended to be made in three different calibers (7.62x39mm, 5.56 NATO and 6.8x43mm SPC Rem.), but only 5.56 NATO rifles are currently produced, with 300 BLK soon on the way.

This article will address the A2 select-fire version for LE/MIL and the semiauto S1 Carbine.

Gun Details

The Bren uses a sturdy, monolithic receiver milled from a 7075 forging with an integral, full-length MIL-STD 1913 rail on top. Two finishes are offered: black hard-coat anodizing or flat dark earth that uses a Cerakote-type product. The trigger housing and magazine well are polymer. Two magazine wells are available: the standard version that accepts M-16/AR magazines and has a similar push-button-style release; and a European version that fits proprietary CZ magazines and has a paddle-style release just ahead of the trigger guard. A kit to change from the U.S. to the CZ variant is available from CZ USA for $150 and includes a magwell and five magazines.

Staked pins on the gas block keep them from migrating out.

The Bren uses a short-stroke, gas-piston operating system with a rotating, seven-lug bolt that resembles the bolt used on the M-16. The gas system is made of stainless steel, with the tube and piston mounted above the barrel. The gas block has a regulator that can be set for normal or reduced gas operation. It is usually used when the rifle is equipped with a suppressor that typically increases gas pressure.


Reflecting the long, all-metal receiver and gas-piston operating system, these firearms are not lightweight—8.43 pounds for the S1 and 7.52 pounds for the A2 (without a magazine). Both are also compact (39 inches for the S1 and 30.7 inches long for the A2 with the stock unfolded and set to the shortest length of pull). With the stocks folded, the S1 is a mere 28.5 inches, while the A2 is 23. Both firearms can be fired when folded, which is an important tactical feature. CZ uses cold-hammer-forged barrels in all of its small arms production, and forged barrels are proven to last longer than conventional barrels. (FN also uses cold hammer forging in its M4 and machinegun barrels.) The A2 barrel is 11 inches long and chrome lined; the S1 is 16.2 inches and without chrome. Both are a slim, .545 inch in diameter and have a two-chamber muzzle brake and a 1:7 rifling twist typically used to stabilize longer bullets in the 62- to 74-grain range.

Lock, Stock and Barrel

The A2 and S1 barrels have different muzzle threads. The S1 uses the more popular thread of ½x28, and the A2 uses 14×1 LH metric (early imports of the semiauto were called the “Bren PS1” and were classified as pistols, because they didn’t have a stock. They used 14×1 LH metric threading). Although the barrel isn’t a quick change, it can be replaced without special tools or a vise by removing six hex-head screws on the sides of the receiver. This feature is a big plus for those who wish to change to 300 BLK, which requires only a change in barrel because it shares the same magazine and bolt as the 5.56 NATO. The Bren uses a side-mounted reciprocating charging handle that can be easily switched from the left to the right side. Reciprocating charging handles make chamber checks easier and can be used to seat a partially chambered round, thus negating the need for the separate forward assist found on an AR. However, they can also cause stoppages if their motion is impeded by situations such as the operator’s grip or when contacting a barricade that the shooter is using for cover.

The muzzle brake/compensator is loud—as can be expected from sideways venting.

The action on the Bren remains locked open after the last round is fired, but the bolt catch works differently than the one found on the AR. While the AR’s catch is dual function—it both locks and releases the bolt—the Bren’s catch only locks the bolt rearward when it is depressed—but it does not release it.

To chamber a round when the bolt is locked to the rear, the charging handle must be retracted and released. Both the S1 and the A2 have an ambidextrous safety/selector. The A2 selector offers 0-1-2-F with automatic fire of 750 rpm. The safety locks the action closed when engaged, thus requiring the firearm to be placed into “fire” mode to clear the chamber. This system is shared by the CZ Scorpion and the AK-47. Magazine release buttons are ambidextrous.

The plastic shell deflector works well to keep brass clear of left-handed shooters. Note the fence around the magazine release to protect it from accidental release. Removing the pin to its left allows the magazine well to be slid downward off the trigger housing to allow replacement with a different housing that accepts CZ’s proprietary magazines.

The Bren has a stock that folds to the right and is adjustable for four lengths of pull. It also has a removable cheek piece that snaps over the comb. The grip has a back strap that can be replaced with a larger size for $12. Dual-sided sling mount plates are at the front and rear of the receiver and accommodate either a 1-inch-wide sling or HK-style sling clips.

The Bren is equipped with removable, adjustable aluminum sights. Out front is a post with round protective ears, while the rear has two apertures: a ghost ring for CQB and a smaller aperture for precision aiming.

Windage errors are corrected using the rear sight, while elevation is adjusted by rotating the front post using a four-prong M-16-style tool or bullet tip. Both front and rear sights can be folded down when optics are used or for more-compact casing and transport.

The most significant difference between the semiauto S1 and the select-fire A2 is the fire control system: The A2 requires additional parts in the trigger group and a different bolt carrier. The trigger group on the A2 has a modified hammer and a burst ratchet and auto sear. The bolt carrier also has an extension at its rear—the “auto sear trip.” In brief, here’s how it works: In semiauto fire, the hammer is held rearward by the disconnector until the trigger is released, whereupon the trigger sear mates with the hammer sear and retains the hammer in its cocked position. Because the trigger is held rearward, it does not connect with the hammer. However, the disconnector makes this connection until the trigger is released and reconnects with the hammer.

The trigger sear engages a rear hammer hook resembling the AK-47 design.

Without a disconnector, the hammer would follow the bolt carrier forward, causing doubling, failures to fire or out-of battery firing. (This malfunction is called “hammer follow” for that reason.) In “full-auto” mode, the disconnector is made inoperative, but the auto sear catches the hammer and holds it rearward in the cocked position. As the bolt carrier comes forward during counter-recoil, the auto sear trip activates the auto sear, allowing the hammer to fall. The trip is located at the rear of the bolt carrier to ensure that the action is close to being fully locked by the time the hammer reaches the firing pin. This negates the possibility of hammer follow. In “burst” mode, a ratchet allows full-auto fire for a given number of cycles; in this case, two for the A2 when in “two-shot” burst mode.

Range Time

The S1 was tested for accuracy and reliability. It was reliable with all five different loads used, including steel-cased ammo that was relatively underpowered. Accuracy was tested by mounting a Leopold Mark IV 8.5-25X50mm scope and firing off a Caldwell Tack Driver rest and sandbag from 100 yards. The S1 showed very inconsistent performance—shooting average groups of 2 to 4.38 inches, with the smaller groups always shot on a cold barrel. Some of these groups had a concentration of several rounds in a tighter group, with two fliers consistently opening it up. With a 1:7 twist, one would think that the heavier, 75-grain Hornady match load would shoot the best, but my sample carbine did not work well with this otherwise very accurate load.

Fire control on the A2 is semi, two-round burst and full auto with a rate of fire of 750 rpm that is roughly equivalent to the M-16.

The best groups were shot with the Black Hills 60-grain V-Max load, with best/average groups of 1.88 and 2.0 inches.

This load also produced an interesting five-shot group, with four rounds dropping into a dime-sized hole and a heart-breaking fifth round landing 3 inches wide to spoil an otherwise perfect target!

The additional 5.2 inches of barrel length on the S1 Carbine over the A2 produced a material increase in velocity that ranged from 151 fps for the Federal 55-grain ball to 254 fps for the Black Hills 60-grain V-Max. Both the S1 and A2 had smooth trigger strokes but had lots of creep and a fair amount of overtravel.

The A2’s trigger was much better (4.5 pounds), compared to 5 pounds, 10 ounces for the S1.

“The additional 5.2 inches of barrel length on the S1 Carbine over the A2 produced a material increase in velocity…”

The bolt catch (located above the magazine release) can be pressed to lock the bolt to the rear, but pressing it will not release a bolt that is already locked to the rear, as on an AR15. Instead, the charging handle must be pulled to release the bolt.

Accuracy and Ergonomics

It should be noted that the Bren’s mediocre accuracy was not the result of poor workmanship, because this rifle uses durable materials and has high-quality machining and precision parts fit (no cost-cutting MIM parts are used, which is unusual). Rather, the Bren’s design necessarily limits its accuracy—with a thin, easily heated barrel having greater muzzle whip than heavier barrels; a gas piston system that induces inconsistent barrel vibrations; a trigger with lots of creep; an imprecise break and noticeable overtravel; and a tactical buttstock with some looseness and a small comb that can’t provide a full cheek weld when firing with a magnified optic.

Takedown is quick and easy. Note the stainless steel gas tube and piston. The receiver is milled from a 7075 forging and attaches to a polymer trigger housing with a single push pin. This aluminum-overpolymer approach is also used by FN on the SCAR series rifles, but the Bren receiver is far sturdier.

With that said, it’s clear that CZ’s main focus was on reliability, with accuracy being a secondary concern; “combat accuracy” is good enough. Ergonomics of the controls could be improved. The grip backstrap is curved in a way that doesn’t ideally fit, making it difficult to apply uniform tension between the top and bottom of the firing hand. Also, the safety lever is way too stiff to be placed into “safe” with the thumb and requires using the support hand. The selector on the A2 contacted and scraped the trigger finger when in “burst” and “full-auto” modes, especially with left-handed shooters. The left-side bolt catch has a fence surrounding its lower side that makes it fairly difficult to use. That’s a problem if the shooter is wearing gloves that reduce dexterity or has an injured hand and needs to lock the action open to clear a jam.

“… it is certainly a contender for a home-defense weapon when loaded with appropriate ammunition.”

Finally, the magazine release button is too far forward (about ¾ inch more than the AR-15), which slows down mag changes for those with average-length fingers and necessitates using the support hand to operate it for those with shorter fingers. Two items to remember when firing the Bren: Do not to use a “thumb-up” grip with your support hand without moving the charging handle to the opposite side. In addition, it’s best to install covers on the side and bottom Picatinny rails, which are sharp and easily abrade the hand.

Robust, Reliable… and Quirky

The Bren is a well-made, robust and reliable rifle with some interesting—and sometimes quirky—elements. Its feature-laden design accommodates right- and left-hand operation. For many, the semi-auto S1 Carbine is certainly a contender for a home-defense weapon when loaded with appropriate ammunition. For those who are accustomed to the AR-15, however, training and familiarity are necessary to become instinctive and proficient in its operation.

The Bren can be fired with stock folded; doing so makes the carbine shorter than 30 inches long.




Group Size (inches)



Black Hills 60-grain V-MAX



American Eagle XM193 55-grain FMJ



Hornady Match 75-grain BTHP



NOTE: These are sizes of best and average five-shot group in inches shot by the Bren S1 Carbine at 100 yards from a Caldwell Tack Driver rest and measured center to center.




Mean Velocity (fps)

S1 Carbine


Gain with

S1 Carbine

Black Hills 60-grain V-MAX




American Eagle XM193 55-grain FMJ




Hornady Match 75-grain BTHP




NOTE: Velocity was measured 15 feet from the muzzle with an Oehler 35 chronograph.




BARREL: 16.2 inches
OVERALL LENGTH: 39-inch stock, open and collapsed
WEIGHT: 8.43 pounds
SIGHTS: Windage-adjustable rear aperture; elevation-adjustable protected post front
STOCKS: Polymer
ACTION: Semi-auto
MSRP: $1,999


Editor’s note: A version of this article first appeared in the October 2017 print issue of Gun World Magazine.