The Colt CK901: The Mystery Colt of Yemen

The Colt CK901: The Mystery Colt of Yemen


ABOVE: The author firing a full auto burst with the Colt CK901. Notice the four fired cartridge cases ejecting from the rifle and how flat the muzzle is. Very little recoil compared to a standard AKM.

The industry does have its share of “ghost guns”, or guns they get a slight glimpse at but never much info at all. Some of these guns are the industry’s best kept secrets. The Colt CK901 fits right into that role. One picture leaked out on the internet of a writer shooting a strange looking rifle with an AK-type magazine at the Colt research and development range. The groups on the web speculated what it was.

The CK901 or the Colt Kalashnikov 901 was designed specifically for one customer, which was the Yemeni Republican guard. They have large existing stocks of AK47/AKM rifles and wanted a better rifle, one that they could use their existing ammo and magazines in. In the 1990’s, Colt introduced a Colt Sporter rifle chambered in 7.62x39mm. This was to offer a rifle capable of hunting medium game such as deer but also to take advantage of the large influx of inexpensive 7.62x39mm ammunition. All good in theory and from a marketing standpoint but there was one giant hiccup; the magazine.

The Colt CK901 is the newest development by Colt. Notice the AK magazine as well as the Colt monolithic receiver. The rifle uses the VLTOR Modstock.

The AR magazine well is straight for several inches. The 7.62x39mm cartridge case has a severe taper compared to that of the 5.56x45mm cartridge. This caused severe stacking issues in the magazines. Colt sold the rifle and conversion uppers with straight magazines based off of their 20 round 5.56mm magazine. Put 5 rounds in and the rifle was moderately reliable. The aftermarket companies started making 30 round magazines. At this time in the early to mid 1990’s, it was a disaster. The larger capacity magazines were horribly unreliable. Colt discontinued this rifle due to these issues. Another problem was the bolt itself. This was not as much of a problem for Colt as it was for several other companies. The breechface was opened up to accept the larger 7.62x39mm cartridge. This left the locking lug support wall rather thin. Bolts would fracture, locking lugs would break off. Sort of a consequence for trying to make something do a job it was never designed to do.

Colt having this experience, realized that to make a proper AR rifle to fire the 7.62x39mm cartridge they would have to overcome these issues they struggled with two decades ago. Right around this time Colt had introduced their CM901/LE901 series of rifles. This was their new modular 7.62x51mm rifle. The modularity consisted of being able to fire the 7.62x51mm round and then by way of switching to a M16/M4 upper via magazine well adapter the rifle will fire 5.56mm. Two guns in one. They chose the 7.62x51mm configuration to be the host weapon. The most critical reason being the bolt was designed around the 7.62x51mm cartridge case, not the 5.56mm. This also enabled them to make a proper bolt that would fully support the 7.62x39mm cartridge. With the 7.62x51mm magazine well, it gave them much more room to work with to design it to accept a AK magazine. This would solve the reliability issues caused by trying to use an AR-type magazine well.

The CK901 weighs 9.4 pounds and utilizes AK-type magazines. During testing by Colt, they were most impressed by the durability and reliability of the US Palm magazine but the rifle was designed to take almost any AK-type magazine. According to Colt’s testing, the US Palm magazines worked the best out of all the magazines tested and is the preferred manufacturer. The barrel length is 16.1 inches which is ideal for the 7.62x39mm cartridge.

Notice the modified 7.62x51mm bolt to fire the 7.62x39mm cartridge case. Unlike usual AR bolts in this caliber based on the 5.56mm round, the CK901 bolt properly supports the 7.62x39mm cartridge case.

The overall length with the stock fully closed is 34.24 inches and with it extended is 37.5 inches. The cyclic rate of fire is similar to the M4 at 700 to 950 rounds per minute. Maximum effective range is roughly 600 meters. This stretched the effective range of the 7.62x39mm cartridge beyond anything seen before in this caliber on the battlefield. In all reality with an average AKM, many times 100 to 200 meters would be considered normal. The CK901 far exceeds this standard making it one of the most accurate rifles in this caliber class.

Starting with the lower receiver, the lower is based on the CM901 rifle. The stock is the VLTOR Modstock with the standard 6-position receiver extension. The buffer chosen is specifically designed and marked “7.62x39mm.” It is made up of several proprietary weights and dampeners and is a prodigy of the CM901 system. The standard M4 pistol grip is used with the traditional winter trigger guard. The fire control group is the select-fire SAFE, SEMI and AUTO positions but can be had in BURST or SEMI only. The selector lever is ambidextrous and positions are marked on both sides of the rifle. Due to the use of the AK-type magazines, there is no bolt catch on this rifle. The AK magazines do not permit the use of an AR-type bolt catch. The magazine release is similar to that of an AK but much smoother. It would also be considered ambidextrous. According to Colt, the magazine catch is a complex system and more difficult to assemble for mass production. As previously stated, Colt test engineers tested numerous magazines and found the US Palm to be the finest they tested. All CK901 rifles were supplied with US Palm magazines but were compatible with the magazines in the Yemeni arsenal.

The lower receiver is manufactured from 7075 T6 aircraft grade aluminum like all Colt AR-type rifles. Due to the low number of rifles bought by the Yemeni forces, all of the upper and lower receivers were manufactured in the Colt model shop.

The charging handle is the new Colt ambidextrous charging handle. Much consideration was put into the design of this rifle to make it as fully ambidextrous as possible. In looking at the design of this rifle, the charging handle was the only issue this author had with this incredible rifle. Due to there being no bolt catch, the shooter is forced to unshoulder the rifle each time the magazine is changed. The shooter would hear the “Click”, drop the rifle down and release and remove the magazine. Now rock the new magazine into place. The charging handle now must be fully retracted to load and then the rifle goes back up to the shooters shoulder. If the charging handle would have been mounted to the right side of the front of the bolt carrier, the shooter could maintain the rifle in the shouldered position, change out the magazine and charge the rifle without the butt of the rifle leaving his shoulder. All actions could be made with his right or left arm. Also clearing malfunctions would be much faster as well with a side charging handle. But there are many ways to accomplish the same task. Colt had planned on designing a bolt catch into the CK901 for US use and possibility for the commercial market. As of this writing the CK901 has yet to be introduced into the LE and commercial market.

The bolt carrier group itself is also modified for the 7.62x39mm cartridge. The bolt carrier is similar to the CM901 with a couple changes. Due to the much lower pressure of the 7.62x39mm cartridge than the 7.62x51mm cartridge there were changes in the exhaust ports on the bolt carrier. The CK901 has only one exhaust port and one small weep hole. None of the CK901 integral parts are interchangeable with the CM901 or LE901 rifles. Like any Colt rifle, the bolt carrier and key are manganese phosphate finished with the inside of the bolt carrier and carrier key being chrome plated. There are forward assist notches on the bolt carrier which functions extremely well if the mechanism needs to be used. The bolt is obviously modified for the 7.62x39mm cartridge case. The bolt is test fired with a proof cartridge and then magnetic particle inspected (Magnaflux) to ensure against stress fractures. The extractor is highly modified and well executed. The extractor claw is enlarged over any previous designs and grabs more material of the cartridge case rim.

The heavier extractor spring and buffer are used as well as a rubber “O” ring to enhance extraction. The firing pin has a robustly modified shape as well as a spring. The 7.62x39mm cartridge offers some additional challenges over NATO ammunition. First is primer hardness. Most Warsaw Pact ammunition uses a much harder primer due to the weight of the AK firing pin (without spring). If the primer was normal, the gun would be at risk for slamfire from the inertia of the firing pin alone. Second is much of the ammunition produced in this caliber use corrosive primers and or propellant. Chrome plating of the bore, chamber, carrier key and bolt carrier are critical to ensure the rifle does not rust due to this condition.

The Colt CK901 lower receiver uses a proprietary buffer for the 7.62x39mm cartridge. Notice the grooves on the front of the magazine release lever. The VOLTOR Modstock is one of the finest and most durable stocks in the industry.

The upper receiver is of Colt designed monolithic upper receiver. It should be noted that the lower handguard is removable so I guess that would be a 2-piece receiver! The main upper is manufactured from a single solid aluminum forging (7075 T6 aircraft grade aluminum). Top rail is a continuous Mil-Std-1913 rail. There are four QD sockets on the handguard area for insertion of a QD sling swivel. The handguard accepts removable Mil-Std-1913 rail segments. This is a good system because the shooter only has rail where it is needed. The upper is equipped with a forward assist, fired cartridge case deflector as well as ejection port dust cover. The cartridge case deflector is machined with a slot cut in it to catch and deflect the 7.62x39mm cartridge case.

The 16.1 inch barrel uses a midlength gas system. The muzzle device is a Smith Enterprises Vortex flash hider. This is perhaps one of the best flash hiders in the industry. This author has tested these in the night and little-to-no flash signature is visible. The crude Warsaw Pact propellants prove a challenge for the Vortex flash hider but it for the most part overcomes it. The front sight base is a Colt folding front sight with a sliding lock. There is a bayonet lug. Due to the midlength gas system the bayonet lug is in the proper location to accept a bayonet slid over the Vortex flash suppressor. The barrel is test fired with a 7.62x39mm proof cartridge and then magnetic particle inspected to ensure against stress fractures. The barrel has a chrome plated bore and chamber, and a 1 turn in 12 inch twist with 6 lands and grooves right twist to optimally stabilize the projectile. Barrel life on this rifle will not be the same as the standard M4 due to the ammunition. Much of the Warsaw Pact made 7.62x39mm ammunition use a steel jacketed projectile which will wear a barrel faster than the NATO copper jacketed projectiles. If not properly maintained, the corrosive salts from primers and propellants could pre maturely wear and or corrode the rifle as well. The rear sight is manufactured by Troy Industries.

SAR had the opportunity to get a firsthand look and test fire the CK901 at the King Abdullah Special Operations Training Center in Amman, Jordan. In looking at the rifle it was exactly the quality one would expect from Colt. Fit, finish and balance were impeccable. This rifle was used for demonstrations for the multiple special operations soldiers there from across the world. Originally the rifle was tested using the US Palm magazine. During some rough handling (slam loaded repeatedly by several of operators) one of the feed lips on the magazine broke. They obtained some Russian magazines from the base armory to continue shooting. The ammunition available was oddly enough the Remington UMC 7.62x39mm 123gr FMJ. The cyclic rate of the CK901 is set to be 700 to 950 rounds per minute. When firing this rifle on full auto, the cyclic rate was most certainly on the real low end of this. Perhaps even below 700 rounds per minute. It appears as though the UMC ammunition has a much lower port pressure than that of Warsaw Pact/Soviet specification 7.62x39mm ammo. The rifle functioned without issue. The low rate of fire was very noteworthy and again this is not a reflection on the rifle. Traditionally UMC ammunition is lower on port pressure, this author has noticed this when firing 5.56mm on fully automatic comparing it to NATO specification ammunition. The recoil of the CK901 was certainly less than that of the AK47 and to someone of my large frame, the CK901 was much more comfortable to shoot.

Shown is the modified LE901 bolt carrier group to fire the 7.62x39mm cartridge. Notice only one exhaust port and one small weep hole in the bolt carrier.

We were shooting off hand at 50 yards, the opportunity did not exist to do any precision shooting. All rounds hit right in the center of the target, the rifle was equipped with a Trijicon Gen 2 Compact ACOG. This premium optic complimented the rifle. It featured a red fiber optic. The combination of platform design, optics and caliber gave this weapon system a very user friendly character.

Colt showed the CK901 at SHOT Show 2016 along with a 7.62x39mm rifle based on the LE6940 which utilized the AR-pattern 7.62x39mm magazine. They received many inquires as to if and when the CK901 may be offered on the civilian market. Colt has yet to give a final answer as to when or if the CK901 will become offered to this market but does say the other rifle with the AR-based magazine will be. The CK901 is perhaps one of the most significant rifles to come out of the West Hartford plant in many years. It is a true new design that took a demand for a military grade AR-type rifle in the 7.62x39mm along with the requirement to use standard AK magazines and put it in the field.

According to sources, the CK901 was extremely well received. According to Colt sources, within the first 24 hours of the rifle being put into service in Yemen, the Yemeni Republican Guard dispatched more than 200 insurgents. Its main attribute was the accuracy upon targeting.

Colt has come to market with some new weapons platforms. The LE901 has been expanded into the M.A.R.C. 901 Series which expands upon the LE901-16S providing the flexibility of the 7.62 to 5.56mm barrel interchange with a more cost effective 7.62mm upper receiver putting the MSRP between $1399 and $1999 compared to $2599 of the LE901-16S. This puts Colt in a competitive pricing with other industry options for 7.62x51mm (.308 Win) caliber semi-automatic rifles. The industry would certainly be hot on the CK901, we just have to wait and see if Colt releases it to the market.

Shown is a picture of an early prototype CK901 with the US Palm magazine which Colt equipped each rifle that went to Yemen.
Close up of the left side of the Colt CK901 receivers. Notice no bolt catch lever and the magazine release lever in front of the trigger guard.
Close view of the right side of the receivers of the CK901. Notice the ambidextrous selector as well as the newly designed bolt carrier for the 7.62x39mm cartridge. Notice there is no magazine release button in the traditional location but in front of the trigger guard.