M k.18 Mod 0/1 CQBR

                          M k.18 Mod 0/1 CQBR


                              Caliber: 5.56 × 45mm M855 / M k.262

The Close Quarters Battle Receiver (CQBR) is a replaceable upper receiver for the M4A1 carbine. Its purpose is to provide naval special forces with a short-length and light-weight close combat weapon that can be used with the SOPMOD M4 tactical attachment. Completely versatile, minimizing the workload of logistical maintenance.

This short-barreled M4A1 conversion kit was designed by the U.S. Naval Surface Warfare Center in Crane, Indiana . Although the length of the M4A1 is already shorter than the standard M16 series, it is not suitable for all missions. Such as VIP protection, urban combat or indoor close combat (CQB) and other situations. The CQBR uses the modular function of the M16 series to allow users to adapt to the needs of the mission by replacing the upper receiver of the existing weapon to turn it into a short assault weapon that is the size of a submachine gun but fires rifle rounds. There were several Special Purpose Receiver (SPR) items included in the SOPMOD Block II kit at the time, and the CQBR was one of them. When the M4 modified with the CQBR did not have an official name, it was called the NSWC CQB M4 or NSWC Crane M4 or other similar informal names by some, but as the special purpose rifle was converted by replacing the special purpose receiver, it was designated as the Mk. 12 Mod 0/1, later the U.S. Navy designated a complete indoor close quarters rifle (Close Quarters Battle Rifle, still abbreviated as CQBR) that had a CQBR receiver replaced as Mk.18 Mod 0.

The CQBR entered service in 2000. At first, it was only issued to the Navy's special forces as a standard weapon for VBSS missions. Later, the Army's Delta Commando, Green Berets, FBI's HRT, etc. also began to equip it. The Mk.18 MOD0 is equipped with the U.S. Navy's Explosive Ordnance Disposal Team (EOD), sailors responsible for ship security, etc. In addition, there are also manufacturers on the market that provide clone gun products with similar designs for civilians and PMC companies to purchase. However, according to DEVGRU retired Kyle Defoor, the need for this kind of CQBR was actually raised as early as the mid-1990s, but it was not until 2000 that NSW Crane designed the CQBR.

In the mid-1990s, the M4A1 was fully equipped, and SEAL Team 6 (the predecessor of DEVGRU) was quite satisfied with it. They especially believed that the matching KAC quick-release muffler was efficient and easy to use. To paraphrase Kyle Defoor, at that time, Team 6 used it in almost 100% of its missions. A silencer was used. This situation changed after Team Six deployed to Bosnia. After the Bosnian War, Team Six began to deploy to Bosnia to carry out war criminal arrest missions. In the early intelligence operations, various disguised reconnaissance missions required members of the six teams to travel in plain clothes; and when performing reconnaissance missions in vehicles, an automatic weapon with powerful firepower that is readily available in the vehicle is needed to facilitate identity exposure. Finally, you can suppress the enemy's firepower and buy yourself time to retreat. At the same time, during the capture mission, although the M4 is more suitable for CQB missions than the M16, it is not the same after adding a silencer. The above various mission environments required an M4 with a shorter barrel, so the Sixth Team approached NSW Crane and proposed the research and development requirements for the shorter M4. This led to the CQBR that was later equipped with special forces of various services.

But there is an "Over gassed" problem here (referring to the problem that the M4A1 and CQBR with short barrels have increased chamber pressure when a silencer is installed, causing too much gunpowder gas to enter the weapon's action mechanism. The consequence is that the weapon is easier to It becomes dirty, the failure rate increases, and there are problems such as gas leaking from the charging handle and hitting the shooter's face). Therefore, the M4A1 using a silencer requires more and more frequent maintenance than the M4A1. In fact, the original intention of Delta Force to cooperate with HK Company to develop the HK416 was not because they believed that the M4A1 was not reliable enough, but because they were looking for a short barrel AR with fewer problems after being equipped with a silencer.

Although CQBR is designed for indoor close combat environments at a distance of tens of meters, it can be used even in a more open environment. In recent years, more and more special operations units have replaced M4 with CQBR. JD Potynsky, a retired Army 3rd Special Forces Group (3th SFG) member, was quoted as saying: "My unit is responsible for direct attack operations (Direct Attack Operations). Action) mission. Our main method of penetration is by vehicle. This means that most of our actual threats are within a 100-meter radius. This also means that we have vehicle-mounted weapons. (.50 machine gun or Mk19 grenade launcher) vehicles are never more than 200 meters apart... Since our mission requirements rarely require us to engage with the M4 beyond 150 meters, when we receive the Mk18 on board. When the magazine was released, many people, including myself, switched to this shorter, more maneuverable and flexible weapon platform. Using standard bullets and our shooting skills, it (Mk18) can perform comparable to SOPMOD (Mk18) when we perform missions. This refers to the accuracy of the M4 and its faster reaction speed in small spaces.”

Interestingly, a member of the U.S. Army Special Forces once posted his CQBR rifle on social media and said that the Army has never been equipped with the Mk18, and the Navy’s weapon is called the Mk18. The Army is only equipped with a "short upper receiver" M4A1". On the surface, this issue seems to be the pride of Army soldiers in the atmosphere of the US land and sea struggle, but in fact the Army still uses weapons such as Mk19 that were standardized by the Navy. There is no weapon that does not use the "Mk" prefix name. The real reason may be related to Americans’ love of word games:

First of all, the US military’s identification of AR guns is based on pressing the receiver, so the model, gun number, government property information, etc. are all engraved on the lower receiver, while the upper receiver can be counted as an accessory ( here is another Examples can deepen readers' understanding. For details, see the explanation of the inclusion of the Reaper 33 upper receiver as a SOPMOD II accessory in AD-15 ). Therefore, the CQBR upper receiver with a 10.3-inch barrel purchased by SOCOM cannot be counted as a gun, but as an accessory. SOCOM distributes this SOPMOD accessory to its subordinate units, allowing special forces to install this accessory on the lower receiver of the M4A1 according to the needs of the mission. The M4A1 equipped with this "accessory" is called the CQBR gun in the M4A1.

On the other hand, what the U.S. Navy ordered actually replaced the entire gun with this upper receiver. The method was as follows: the Navy handed over the M16A1 in stock to the supplier, and the supplier replaced these M16A1s with CQBR specification upper receivers. (But unlike SOCOM, the barrel in the Navy order is 10.5 inches long). At the same time, the MK18 and anchor marks are marked on the side of the lower receiver magazine socket - this approach is similar to the US Air Force's transformation of old guns into GUU- 5/P , it is the same as striking out the original gun type on the lower receiver and adding "GUU-5/P" in the empty space. However, the Navy has more information to engrave, so it is not like the Air Force who just prints it on the receiver. Instead of adding engraving to the left space, add engraving to the right side. In short, what the Navy purchased was a complete gun called Mk18, not accessories.


Therefore, the storage numbers of CQBR and MK18 are different. The NATO Stock Number (NATO Stock Number) of the CQBR upper receiver is 1005-LL-L99-5996, while the National Stock Number (NSN) of a complete Mk18 short carbine is 1005-01-527-2288 . The ordering unit for the former is SOCOM, and the latter is the Navy (it is reported that the Air Force has also ordered).


CQBR upper receiver

Mk18 Mod0 complete gun

Ordinary M4A1 (top) and the "short upper receiver M4A1" with CQBR replaced (bottom)


For ordinary SEAL M4A1 gun cases, each M4A1 is equipped with two upper receivers, one long and one short. You can decide which combination to use based on mission needs or personal preference.

A Green Beret soldier showed off the "short upper receiver M4A1" in their unit online. He said that the Army has never equipped the Navy's MK18. From his description, the Green Berets are the same as ordinary SEALs. Each M4A1 is equipped with two upper receivers, one long and one short. You can decide which combination to use based on mission needs or personal preference. Since the lower receiver does not change the receiver inscription like the sailor's MK18 on the ship, the Army does not call this weapon MK18.

The Mk18 purchased by the Navy has the Mk18 mark engraved on it, while the CQBR purchased by SOCOM allows users to install it on their own M4A1 lower receiver, so there will be no Mk18 mark.


Note the Mk18 MOD0 mark on the magazine holder in this picture. This is the weapon of the US Navy Ships boarding Teams.



The barrel length is only a little over 10 inches, which is shorter than the 11.5-inch barrel of the Colt 733/933. Compared with the CQBW M4 system with a 14.5- inch barrel, the Mk18 is actually a true CQBW M4. But the improvement of CQBR is not just about shortening the barrel. Its main improvements are as follows:

Barrel: Using a 1:7 twist rate M4 barrel, there are actually two barrel lengths. The CQBR upper receiver provided by Colt has a 10.3-inch (about 262mm) barrel, while the Lewis Machine and Tool Company (Lewis) The Mk18 barrel provided to the Navy by Machine & Tools (LMT) is 10.5 inches (approximately 267mm). The diameter of the barrel is 0.625 inches (16mm) inside the handguard. A KAC QD flash suppressor is installed in front of the barrel, and a KAC QD silencer can be used (NSN code 1005-01-437-0324). Although the bayonet bayonet is retained, the CQBR cannot be equipped with a bayonet.

Gas guide device: The diameter of the gas guide hole was expanded from 0.062 inches (about 1.6mm ) to 0.070 inches (about 1.8mm ) to alleviate the problem of increased pressure in the gas guide holes caused by the short barrel, and the design of the gas guide hoop was changed.

Bolt: A one-piece McFarland bolt gas ring replaces the original three-piece gas ring assembly.

Shell hook: The standard 4-turn shell spring is changed to a 5-turn shell spring developed by NSWC. Currently, manufacturers have provided commercial finished products for sale. Use an O ring to surround the shell spring (the previous content is collected from WIKI, but former Green Beret member Jeff Gurwich said that there is already such an improvement on the SOPMOD M4. The reason is that the chrome layer of a batch of barrels is too chromium-plated. Thick, affecting normal shell extraction. Then I used a new shell extraction hook spring and this rubber ring to increase the shell extraction force).

Charging handle: PRI's M84 Gas Buster charging handle is used. This charging handle enlarges the size of the charging handle lock, but its main function is to deflect gas flow. Because the AR system has an inherent shortcoming, when shooting with a silencer, gunpowder gas will overflow from the charging handle groove and hit the shooter's face. So some manufacturers have produced replacement products that can deflect these gases, and the PRI M84 Gas Buster charging handle is one of them.

Mechanical sights: In order to facilitate the installation of optical sights, and because it is a close-combat weapon and does not require the KAC's 600-meter independent rear sight, the original design was to cut off the detachable handle, leaving only the rear sight seat. However, most of the current CQBRs are replaced with finished rear sights similar to the cut-off handle produced by Lewis Machine & Tools. Interestingly, according to Kyle Defoor, the method of sawing off the handle itself was a "little invention" of the DEVGRU team members. At that time, no manufacturer produced a folding rear sight for the AR-15. In order to be able to install a red dot mirror while In order to protect the mechanical rear sight as a backup, they sawed off the handle themselves and only kept the rear sight seat. As a result, it has become "standard equipment", and there are companies that produce this type of rear sight mount for sale.

Stock: A variety of M4 telescoping stocks are currently used on the CQBR, but the most common is the SOPMOD stock, commonly referred to as the "Crane stock", designed by Dave Armstrong of NSWC-Crane )design. The stock has a comfortable cheekrest and two storage compartments for backup batteries. This stock was originally made from fiberglass polymer by NSWC-Crane, but it was prone to chipping. The current Crane stock is supplied by LMT (hence the name LMT stock) and does not have the problem of chipping. . Not all shooters use LMT stocks, some still use Colt stocks, and some people now replace their CQBR rifles with Magpul M93B stocks or other stocks.

Handguard: The original standard handguard for CQBR and Mk18 MOD0 is KAC's RIS (NSN code 1005-01-416-1089), which can be installed with any accessories that comply with the MIL-STD-1913 Picatinny rail interface, Navy special The troops mainly distribute accessories ordered in the SOPMOD system. Later, some CQBR rifles were replaced with VLTOR's CASV free-floating handguard. When SOPMOD II finally decided to use DDL's RIS II handguard, many Mk18 MOD0 (or the Army's M4 CQBR) also used RIS II handguards or DDL's upper receiver. Initially, some people thought that there was no Mk18 MOD1. It’s just that some players and manufacturers call this type of Mk18 this way. But later, more and more evidence confirmed that Mk18 MOD1 does exist (including the name in some procurement documents), but the actual finalization time may be between 2013 and 2015. In other words, the RIS II handguard was installed before that Still MK18 MOD0. However, because some wealthy companies are dissatisfied with DDL upper receivers, they will purchase handguards or upper receivers produced by other companies, such as TORY .

Ammunition: The CQBR is designed to use standard 5.56×45mm NATO standard 62 grain M855 regular rounds and M856 tracer rounds. However, due to the low muzzle velocity due to the short barrel, the heavier 77-grain Mk . 262 bullet is the first choice.

Lower receiver: The lower receiver is still an unmodified standard M4A1 lower receiver, with a choice of semi-automatic and fully automatic modes. However, rifles modified in different periods or rifles delivered to different troops have different treatments for the inscriptions on the lower receiver. For example, some rifles are not changed at all and the Colt M4A1 style inscriptions can still be seen, while other rifles have original inscriptions on the lower receiver. The right side of the blank magazine holder is marked with "Mk18 MOD0", but some guns have other inscriptions, which leads to confusion about the Mk18 inscription. The lower receiver of the later officially finalized MK18 MOD1 will have "18-1" written on it.

Upper receiver: Depending on the barrel, there are two types: Colt receiver and LMT receiver. Therefore, the total length including the barrel is 19.25 inches (489mm) or 19.7 inches (494mm). When the butt is retracted The total gun length is 26.25 inches (666mm) or 26.77 inches (671mm).

               

The left is the original M4A1 air- locking ring, and the right is the new CQBR air- locking ring.

              

The left is a 4-turn tension shell spring, and the right is a 5-turn tension shell spring.

CQBR rear sight with handle cut off

LMT rear sight

LMT’s 10.5-inch barrel

PRI's M84 GAS BUSTER Charging Handle




It seems that there are more and more Mk18s using M16A1 lower receiver + M4 upper receiver on the ship.

HLTVrocks, who served on the CG-70 Lake Ilya, took a picture of the Mk18 with his mobile phone. Although it was not clear, he confirmed that the inscription on the lower receiver of the gun was modified from the M16A1.

To save money, use Mk18 with M16A1 lower receiver

A new photo taken by HLTVrocks in January 2009. This photo is even more interesting. The Mk18 upper receivers pictured here were returned to Crane a few months ago and replaced with standard M4 upper receivers, but the lower receivers are still Mk18 ones.

A MK18 MOD1 with "18-1" written on the lower receiver but equipped with a 14-inch barrel

CQBR with VLTOR handguard and stock installed at the same time


The CQBR upper receiver photographed by SMGLee in the SEAL Armory

CASV handguard is a new accessory for Mk18

CQB M4 with silencer

A CQBR with Mk18 markings on the left side of the receiver, but still has Colt M4A1 markings on the right side of the receiver

The U.S. Navy Special Forces purchased a large number of HK416 steel magazines, and this seems to be one of them

Mk18 or M4 CQBR with DDL RIS II installed

Mentioned in SOPMOD II about the various "short upper receiver M4A1" teammates of that Green Beret Jeff Gurwitch

The modified "short upper receiver M4A1" used by the Army Special Forces (Green Berets) in Afghanistan. The picture on the left is the TROY-VTAC Alpha handguard, and the picture on the right is the TROY Alpha handguard.

Jeff Gurwitch mentioned that more and more people like to install laser pointers further back, because the laser is not like a tactical electric hand, where part of the light beam will be blocked by the handguard or muzzle and silencer, but if it is installed farther back, it can It makes the center of gravity of the gun less forward, and it is also very convenient to hold the gun with C-clamp (also called TOB, thumb pressing barrel position, commonly known as "Magpu grip" in China)

       The lower rail of the DD handguard is removable, so the M203 can still be hung


Mk18 civilian clone gun, and not all clone CQBRs use RIS handguards


After confirming that SOPMOD II uses DDL's RIS II, private players also cloned the same Mk18 MOD0

Mk18 clone gun with Geissele M-LOK interface SMR MK4 handguard

Civilian player’s MK18 clone gun, equipped with URGI handguard

Tintin ’s NSWC Mk18 clone gun from QBQ and C2K Gunmen

Civilian clone guns are not necessarily 10.3 inches. For example, this one has a 10-inch barrel.

In Tintin ’s photography practice in 2015 , his MK18 was also replaced with a DDL handguard, a collection that made domestic AR fans envious and jealous.

The clone CQBR of the ARMS company's SIR handguard used by the bodyguards of the first American "Governor" Brymer of Iraq - the contractors of Blackwater.


































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