Torture Tests: The CZ 807 AI

Torture Tests: The CZ 807 AI


ABOVE: CZ Engineer Martin Sanda puts rounds downrange and brass in the air during the test of the 5.56x45mm CZ 807 AI assault rifle, using a benchrest bipod and Meopta’s “MeoTac” 3-13×50 sniper scope. Photo courtesy CZ.

CZ is an old and highly respected firearms manufacturing company located in the Czech Republic. SADJ is certain our readers are familiar with the many military and civilian products that they have produced over the years; the ZB-26 light machine gun which became the British Bren; the famous CZ 75 handgun, as well as many fine sporting and hunting firearms. We were delighted to have the opportunity to visit the Bzenec Shooting Range and to spend some serious time testing the current version of the BREN series of modern assault rifles. We would like to thank Military Product Engineer Martin Sanda, Gunsmith Pavel Vrága, Sniper Petr Marek, Project Manager David Kreisl, Media Liaison Manager Hana Smilkova and Promotion Manager Jiri Sedlacik among others for their assistance in this endeavor, they made it possible.

Late June, 2015 – Uhersky Brod is located about 300 kilometers southeast of Prague, in the beautiful Zlin forest regions of the Czech Republic. It was easier to fly into Vienna, Austria and drive to the town, than to come down from Prague, and the scenery was breathtaking on the trip. The original “CZ” firearms manufacturing company known as Ceská zbrojovka was re-formed into Ceská zbrojovka a.s. in 1992.

David Kreisl

The introduction of the new style of assault rifle – the CZ 805 BREN – using lightweight alloys and polymers with special characteristics, has led to a new contract to outfit the Czech Army. That program is going well, and CZ is actively pursuing new frontiers for this new style of product. “I” is for “India”

While the CZ 807 series of rifle is an extension of the CZ 805 assault rifle design, there are specific customers in mind for the 807 series. Two customers that CZ is working with are New Zealand (Thus the “NZ” in the serial numbers) and India. Each has specific characteristics that the customers want. The trials in New Zealand required several barrel lengths, about half with 14” and the other half with 16” barrels. The Indian requirement was for 16” only.

It was the Indian requirement for over 65,000 new rifles that initially led to this test, and dictated some of the details. However, the CZ 807 A has a broad appeal to many other customers. The now dormant Indian solicitation included a very difficult requirement that both 5.56x45mm, and a change to 7.62x39mm be available to the soldiers. The Indian Army has been using their indigenous INSAS 5.56x45mm AK based rifles with many reported problems, while many of their soldiers also use AKMs in 7.62x39mm for various situations. Thus, the dual caliber change-out requirement. At SADJ, we’re not convinced that this broad a paintbrush need be used to solve that issue; perhaps the Indian Army might be better served by homogenizing their service caliber to one or the other- The CZ 807 could certainly satisfy either choice they made and simplify the Army’s logistics. Nonetheless, what the customer wants is what the vendors strive to provide, and the CZ 807 series of dual caliber is an outstanding contender.

CZ Engineer Martin Sanda gives the “Thumbs Up” at the end of the test showing his satisfaction with the pile of brass after three days’ work by the testers.

The Gauntlet

When CZ contacted SADJ to organize a Mil-Spec test, this dual caliber situation had to be taken into account. We were aware that the CZ 805 series had undergone many military style tests, in many environments, and had performed exceptionally. There had been tests where massive amounts of ammunition- in the tens of thousands of rounds- had been expended very rapidly. Gossip from the testers involved spoke of high heat (Of course) at these high rates of fire, with the weapons just keeping on firing with little to no problems. While this sounds outstanding to a fighter, it does not provide quantifiable data that a procurement person could use. CZ was asking SADJ to provide a proving ground where not only would the CZ 807 face what Special Operations fighters are looking for answers on, but what do the procurement people, the logistics people who must prepare an army for such a major change, want to know.

The Gauntlet was thrown down, and it was just the kind of thing that we at SADJ knew we were up for.

Our proposed test was for two rifles, one of each caliber, each firing 12,000 rounds. We wanted the following answers for CZ’s customers:

1- Is the CZ 807 AI up to Mil-Spec?

2- Will it perform through a US style Mil-Spec test?

3- Are the parts interchangeable for full function testing?

4- What are the Mean Rounds Between Failures?

5- What is the barrel life and how is the dispersion testing?

6- Can we ascertain that both the logistics groups and the end users will be satisfied with the weapon system?

Petr Marek has been a sniper with the Czech military for many years, and is a skilled marksman. Like all true marksmen, he takes pride in his cleaning regimen. Cleaning is done from chamber end towards muzzle, and the brush is removed before withdrawing. Petr had many procedures he adhered to, but we thought our readers would be interested in this set of 4 cleaning tools he used. The black spray bottle in the back was given to Petr by Gunnery Sergeant Carlos Hathcock himself, at a sniper competition and training event in the 1990s, when the Gunny advised Petr to use this bottle for an alcohol spray. If the Gunny said use it, wise people do.

SADJ could ascertain the Mil-Spec issues and caliber interchange very easily with a properly designed test. Barrel life and dispersion are more related to how that test is performed- leading to the most crucial questions we had to design the test for- elaborated in number 6 above.

Most end users intuitively consider the famous four qualities in firearms that the likes of Eugene Stoner, L. James Sullivan, Reed Knight and many others have polished over the years; is the weapon design Simple, Reliable, Accurate, and Robust? If it doesn’t meet those requirements, it’s hard to get it accepted by the professionals who have to use it. Most end users will look at how reliable it is, and ask whether it can it withstand heavy use- long bursts while they provide cover, “mad minutes” in tough firefights? All questions that when answered, provide confidence and comfort for the warrior who has the weapon as a life-saving or life-taking tool.

Logistics personnel have a different requirement in mind- it’s not all combat, it’s mostly about training sessions, longevity, chain of supply, and cost accounting. The planned purchase of a new weapon system requires many factors be taken into account- and SADJ had to design a test that could answer these questions as well.

The basic operating group; the bolt carrier assembly with piston and spring, as well as the gas plug set.

The tests were designed to answer these questions in a proficient and comprehensive manner. We invite our readers to understand that while this type of test sounds like fun, it is in fact a grueling and demanding task- many hours and many people working to keep the details in order to not invalidate the terms of the test. (Imagine yourself, excited to partake in a 30,000 round handgun live fire test, then discovering that someone has to LOAD all of those magazines, and it’s going to be YOU). It was decided that the best way to proceed was for the factory to provide the firearms, the ammunition, the shooters and technicians and the range, and this author would be in a supervisory capacity to ensure protocols and temperatures were adhered to, and perhaps do some of the test firing.

In order to speed up the testing time, and allow a natural test of barrel erosion and dispersion, CZ provided an air compressor with hose to cool the barrels. It’s important to “Rest” the barrels and return them to an agreed ambient temperature between each firing. For those who want to engage in this type of test, dropping weapons in water or using other methods that cool too rapidly are not effective in getting true results. The need is to simulate years of training interspersed with long periods of no use, not to wow a crowd with clouds of steam. Ambient temperature air sent through the barrels at perhaps 100psi will speed up the removal of heat, and shorten your testing time without compromising the barrels. If you do this type of testing a lot, then remember that compressors mean moisture and add some condensing to the system.

First the gas plug is turned and removed forward, then the gas piston and spring are removed forward.

We utilized one shooter at a time, alternating rifles to allow for the cooling period.

Some of the details of what we arranged for the test firing protocol changed as we discussed the on-going tests with CZ and their engineers. Essentially, they were confident that the temperature on the barrels could go higher than our first recommendation of taking the temperature down to around 80° F before returning to firing. Their engineer felt very strongly on two subjects- first, that we could fire faster than our test protocol, and second, that he did not want any mandatory parts changes- just inspections at the prescribed points. Having run similar tests in other conditions, he was confident in his product. So, we ran the first part of our tests at the prescribed rates, and as SADJ saw the performance of the weapons was superior, we switched the firing rates up, and did away with parts changes.

Days at the Range

A total of 24,000 rounds would be expended, 12,000 of each caliber, and only one rifle in each caliber would perform this. Each day, the temperature was around 77-80 degrees Fahrenheit, or 24 degrees Centigrade. It did not rain, and the humidity was average. Nice days for testers and testing alike.

First the gas plug is turned and removed forward, then the gas piston and spring are removed forward.

The firing sequence would be 90 rounds at semi-automatic for the first rifle, fired 12 rounds per minute. That is an excruciating 5 second wait between firing.

Then, 60 rounds at fully automatic, fired in 5 round bursts with 5 second intervals.

The rifles are switched, and the temperature of the first rifle has the barrel brought down to 80-100 Degrees F before it is returned to the line.

At approximately 600 rounds per rifle, SADJ was satisfied that the cooling periods were longer than necessary, and the CZ engineer’s desire to speed up the testing would work well and not skew the results from the point of view of
procurement personnel.

The firing sequence would be 90 rounds at semi-automatic for the first rifle, fired 20 rounds per minute. That is a 3 second wait between firing.

Then, 60 rounds at fully automatic, fired in 5-7 round bursts with 3 second intervals.

The rifles are switched, and the temperature of the first rifle has the barrel brought down to 120 Degrees F before it is returned to the line.

We continued with this regimen until approximately round 8000 for each rifle, when we stepped up the pace to 90 rounds at semi-automatic fired 40 rounds per minute, then, 60 rounds at fully automatic, fired in 5 round bursts with 2 second intervals. Heat issues at this point were reaching the limits of what the procurement part of the test required, but the rifles showed no negative signs whatsoever.

The basic operating group disassembled for cleaning about halfway through the test. No broken parts are discovered at all, wear was minimal. Note the multi-lug bolt head. On the bolt carrier side there is a clear view of the cam pin path, which dictates the time before bolt rotation begins.

Hasty Defense

The last 5 magazines that we fired were at full cyclic rate- approximately 800 rounds per minute. This was in keeping with the US military’s new “Hasty Defense” test. No problems were encountered other than one double feed that was magazine related. Temperatures on the gas port block, which had been between 450 and 600 degrees F for most of the testing, approached 780 degrees F. High, but not scary high for what the rifles were doing.

Mean Rounds Between Stoppages (MRBS) is determined by dividing the total number of rounds fired by the total number of stoppages. “A stoppage is defined as any unplanned cessation in firing or the inability to commence or cease firing attributable to the gun. All incidents shall be recorded and any considered as not chargeable to the machine gun shall be substantiated by the contractor.” During testing on the CZ 807 AI, we had (4) total stoppages that were properly attributed to the ammunition. Ammunition issues (failure of ammunition) do not count in this type of test. We had one stoppage attributable to a magazine failure to feed, and one extractor issue. The math on that is: 12,000/2=6,000. That’s “6,000 Mean Rounds Between Stoppages.”

Air hose inserted into the chamber end of the barrel. At 100 psi (690 kPa) the barrels cooled down to an acceptable temperature in approximately 3 minutes. Normal ambient air would take about 15 minutes to cool down to an acceptable level. While one barrel was cooling, the other rifle was being fired.

Mean Rounds Between Failures (MRBF). MRBF is determined by dividing the total number of rounds fired by the total number of failures. “A failure is defined as any stoppage which involves part replacement or requires in excess of one minute to correct; or involves any failed or damaged part detected during scheduled preventive maintenance, the replacement of which is not authorized at the crew or organizational level of maintenance as prescribed by Source Maintenance Recoverability Code and TM-9-1005-313-23P.”

The MRBF numbers are the same as for Stoppages, we had only one issue with an extractor that needed changing on the 5.56x45mm rifle. This was a very impressive 6,000 rounds. We had no real failures whatsoever that were related to the firearms parts.

To be clear, the US M4A1 Rifle Mil-Spec test specifications require better than 600 MRBS and 3600 MRBF for performance. The CZ 807 AI clearly performed well above those standards.

Recording temperatures to keep the barrel within the prescribed temperature range is difficult without a quality instrument to read them. This Voltcraft IR 1200-50D with USB provides a -50 to 1370° C (-58 to 2898° F) temperature range which more than covers the temperature range needed here. Quick readings were taken of barrel temperature after each firing, and checked for proper cooling before returning the firearm to the firing line.

CZ 807 A Series

The 807 series is derived from the CZ 805 BREN series of rifles. The basic characteristics of the rifle are that it is a piston operated, gas-driven select-fire rifle of dual calibers. The ambidextrous charging handle is easy to change sides on. It has a modular design, with an aluminum alloy upper receiver and a polymer lower receiver/fire control group. The bolt is a multi-lug type riding in a bolt carrier, locking into a barrel extension. The system is balanced well, and designed to meet the most rigorous modern requirements of an assault rifle.

Top: CZ 807 AI in 5.56x45mm; Bottom: CZ 807 AI in 7.62x39mm. Both stocks are locked in fixed position but not extended.
CZ 807 AI rifles that were used in the test, on the forest floor amidst the pine needles and cones indigenous to the Zlin region forests.
Automatic Fire: as the bolt carrier comes forward, the trip actuator approaches the trip lever. Once it passes and trips the lever, if the trigger is held down then the hammer has been delayed long enough for brass case relaxation and extraction, and the hammer is released. The cycle is repeated as long as the trigger is held back. In semi-automatic fire, the trigger must reset for each round fired. (In the center photo, the trip actuator appears behind the trip lever—in reality, it would ride over the trip lever.)
Left side of the bolt carrier group, fully assembled. Note that the squarish construction speaks of a good design with ease of manufacturing, and the bolt carrier overhangs the bolt itself. This compacts the distance that the piston needs to reach to operate the bolt carrier withdrawal. A clear view can be seen of the cam pin in the side, and the path length and angle it travels in.
Front top view of the trigger group, showing the takedown pin and its detent spring with two positions to retain the pin during assembly and disassembly.
The bolt and extractor are in a familiar, tried and proven style- the extractor takes the place of one of the multiple locking lugs as on the M16, AR-18, SA-80, G36 and many other modern rifles. This photo is at 9000 + rounds, and small amounts of brass shavings show in the picture, as is expected.
Underside of the buttstock- it has multiple extension lengths, controlled by a convenient and easy to use lever.
The main magazine release is on the right side, available to the trigger finger. The button is depressed to drop either caliber magazine, and the button is protected by two ridges to avoid accidental mag-drops. On the left side, however, is another magazine release that works in tandem with the main one using an internal connection. This release is protected inside a well at the front of the trigger guard, and under the bolt release.
Caliber Conversion: The CZ 807 AI complete package- the rifle in 7.62x39mm at top, and the 5.56x45mm caliber conversion below it. One of the best features of the CZ 807 series of rifles is the caliber choice available to the end user. The purchaser can opt to have either 5.56x45mm for NATO compliance, or 7.62x39mm for keeping with existing inventories or ammunition choices. The purchaser can opt to make both calibers available to special users, or start with one caliber to use up existing stores, and switch to another for updating. This situation is especially handy for countries that are based in 7.62x39mm and must supply troops to international missions that require ammunition in 5.56x45mm to ensure homogenous supply with all involved countries’ troops, such as many UN missions. Changing caliber is simple: the barrel assembly, bolt and firing pin, and the magazine are changed out in a field safe operation at the unit level. A special magazine well insert is used to convert from the 5.56x45mm magazine to the 7.62x39mm magazine.
The trigger group of the CZ 807 has a magazine well that is for the 7.62x39mm magazines. To convert to 5.56x45mm, the only item needed for the lower (Trigger group) is the magazine well insert.
Top: CZ 807 AI in its natural caliber of 7.62x39mm, showing the underside of the standard magazine well. Bottom: Converted to 5.56x45mm, showing the insert inside the magazine well. Note that the trigger guard can be adjusted for gloved use.
Top view of the trigger group showing the magazine well insert converting the CZ 807 to 5.56x45mm.
Barrel groups are readily identified by the caliber marking on the gas block- 5.56 for 5.56x45mm and 7.62 for 7.62x39mm.
Both calibers use a common bolt carrier- it is the bolts and firing pins that need to be changed to convert. The bolts are caliber marked, as are the firing pins, but a quick check is to look at the bolt face. The cartridge base on the 5.56x45mm is smaller in diameter than the 7.62x39mm, and in this photo you can easily see that the left bolt is the 5.56x45mm one. (The one on the right is 7.62x39 and has the firing pin extended, this is not a difference in design, just in the position of the bolt during this photo).
Caliber conversion package- these are the components necessary to change caliber on the CZ 807 from 7.62x39mm to 5.56x45mm. The 7.62x39mm package would appear the same except no magazine well insert is needed and the magazine would be more curved. Barrel group and bolt markings would also indicate caliber.
CZ 807 series magazines: Left- 5.56x45mm 30 round polymer magazine- CZ has chosen to use a CAA made M16 style magazine- very reliable, and available off-the-shelf. End users may choose their own M16 type magazine. Right- CZ is manufacturing their own proprietary 7.62x39mm magazine that supplies 30 rounds. Standard AK magazines will not work in the CZ 807, which is due to the design of the receiver. SADJ does not see this as a negative at all- the caliber change capability, along with the reliability of the magazine feeding system used outweigh any advantage of trying to use existing steel magazine in stores.
At the end of firing over 12,000 rounds through each rifle, it was noticed that the 7.62x39mm rifle had a lot of case base markings on it. We had expected a more violent ejection than the 5.56x45mm, and noticed the pattern in brass ejection, but here is physical evidence of the difference. The 5.56x45mm ejection port buffer shows little wear in comparison, if any. For the purposes of an end user, this is hardly a large consideration- a 12,000 round life on the training aspect has hardly left any wear at all on any receiver part. We noted a consistent brass ejection at the 1 o’clock position (Right forward) with some variation to 3 o’clock. This was healthy for the weapon design, and variation was ammunition related.
Accuracy and Barrel related dispersion: In any scientific test, as many variables must be reduced or accounted for as possible. In accuracy testing, we’re looking for how the rounds fired might see a spread of the group- a reduction in accuracy from barrel wear- after certain benchmark rounds are fired. The first thing the tester must do, is to ensure the ammunition used in the test is from the same manufacturer, with the same characteristics, and hopefully from the same lot. In the case of the test at hand, we had two calibers to fire in parallel. Sellier & Bellot ammunition was chosen by the factory. While this author has a healthy respect for the quality of S&B ammunition, SADJ is also aware that these loadings are not sniper grade ammunition- this means that all parties involved knew that there would be a few “Flyers” when firing for accuracy. We did not want to switch ammunition from the test ammunition to a higher grade S&B product, we wanted to stay with our test ammunition to reduce variables. In the following photos, the upper part of the pen shown for comparison is 1.75 inches in length. It can be seen that in both calibers, degradation of accuracy is negligible over the course of fire SADJ put these through.
5.56x45mm- expert marksman and well respected Czech sniper Petr Marek fired the accuracy groups at 50 meters. On the left there are two groups of 5 shots, with each group being approximately 1” in diameter. On the right, after over 12,000 rounds through the rifle, the 5.56x45mm group Petr fired is approximately 1.5” in diameter. This is a negligible degradation in accuracy over that use of the barrel. This would be approximately 10 years of training firing for the average soldier, at 120 rounds per year. Special Forces and those in actual combat units would have a different time/use standard of course, but most soldiers are only in qualification fire on a yearly basis.
7.62x39mm is a different animal from the 5.56x45mm as far as inherent accuracy. Testers expect a slightly less accurate round. In this case, Petr fired the starting set with a fresh barrel showing a group of 5 at about 1.5 inches. After 12,000 plus rounds through the barrel, the group has spread to a little over two inches, with one “flyer” due to ammunition. A very, very acceptable and minimal decrease in accuracy.
CZ 807 AI in 7.62x39mm disassembled.