First Generation
XM8 First Generation Prototype Gun
Due to the technology of XM29 as a foundation and based on G36, the concept research and prototype of XM8 The production of the gun proceeds very quickly. The XM8 prototype gun was officially announced at the US Marine Corps display in October 2003, and the XM8 project name was changed from "Light Assault Rifle" to "Modular Assault System" ( Modular Assault System). The U.S. Army Infantry Center and the Picatinny Arsenal in New Jersey are also actively involved in the development of the XM8. ARDEC stationed at the Picatinny Arsenal is responsible for supervising the production and testing of the XM8 prototype gun. Under the supervision of ARDEC, the Army first obtained 30 XM8 prototype guns in the fall of 2003, and by October received the first batch of 200 XM8 prototype guns. This batch of prototype guns was first conducted live-fire testing at the Aberdeen Proving Ground in Maryland, then sent to Alaska for polar testing in February 2004, and tropical testing in June 2004 (probably in Panama). Finally, it will Sent to Yuma Proving Ground in Arizona for desert testing. The Army requires that the XM8 must be simple to operate and easy to train. Therefore, in addition to Army soldiers, the personnel participating in the live-fire test in Aberdeen also included Marines, pilots, Coast Guard members, and even retired veterans. Jodie Daubert, a spokesperson for the Office of Planning and Management, said that a veteran who had not touched a gun in six years of retirement used an XM8 to shoot a 300-meter target from a standing position, and every shot hit the target.
The overall shape of the XM8 is streamlined and looks like a fish, but the shape characteristics of the G36 can also be clearly seen, so some people may mistakenly think that the XM8 is just a G36 with a changed shape. But in fact, XM8 has greatly improved the G36 and adopted many new technologies from the XM29 research results. It not only improved some of the inherent shortcomings of the G36, but also improved the tactical performance of the G36. It is not so much that it has a different The G36 on the outside is rather an upgraded version of the G36. In fact, the German HK company is also transferring the new technology used in the XM8 to the newly produced improved G36.
Basically, the XM8 is a fully modular weapon system with 4 models: basic, precision shooting, heavy barrel automatic rifle, and compact. The modular components of the XM8 include the barrel, stock, magazine, and sighting system, and these components can be quickly replaced to change into different models.
The gas guide device and bolt of the XM8 are basically the same as the G36. It also uses a short-stroke gas piston system and a rotary locking bolt with 6 locking protrusions. This gas system is derived from the AR-18 and has been improved by HK engineers. About 90% of the gunpowder gas passing through the gas hole will leak forward, and the remaining 10% is used to complete the weapon's action cycle. Since the gas guide system of the XM8 is not as prone to carbon deposits in the gas guide tube and receiver as the M16/M4 series, the reliability is improved. It is said that in reliability tests, a prototype gun has fired 15,000 rounds without cleaning or lubricating, and can cope with most harsh operating environments. In addition, the new design of the XM8 also reduces the workload of maintaining the rifle by 70%. For example, it only takes 4 minutes to maintain an XM8, while it takes 14 minutes to maintain an M4. Moreover, the XM8 has a long maintenance cycle and excellent service performance.
Due to the use of new material technology developed for the XM29, the base XM8 is significantly lighter than either the M4A1 or G36K. The XM8 is very light. The basic model of the first-generation prototype gun weighs 2.84kg (6.25 pounds). This weight includes the sighting device that combines an infrared laser designator and a reflective sight. By comparison, the M4 MWS (Modular Weapon System) weighs 4kg (8.85 lbs) including rails, backup sight, M68 reflex sight and AN/PEQ-2 laser designator.
However, the original target of the basic model of XM8 is 2.6kg (the ideal weight is 5.7 pounds), so HK engineers are still working hard to reduce the weight of XM8.
The comprehensive sighting device used by the XM8 combines a red dot reflective close-combat optical sight (CCO), an infrared laser pointer and an infrared illuminator. One sighting device includes the M68 CCO, AN/PEQ- 2 and AN/PAQ-4 functions. This all-in-one sight reduces the size and weight. There is no need to install different accessories on the rail or different positions of the receiver like the M16/M4, and there is no need to separate them when zeroing the sight. Zeroing each sight can be done at once. However, the aiming device on the first-generation prototype gun only has one function: CCO, leaving only space for other functional modules. The non-magnifying reflex sight allows the shooter to aim with both eyes, making it easy to quickly acquire targets. A backup reticle is etched on the scope so that if the battery runs out and cannot be replenished in time, you can continue to aim and shoot. In addition, in the initial idea of ??XM8, it was required to use a wireless switch to control various functions of the sight. The shooter can install this wireless switch on any part of the gun body according to his own usage habits (the promotional materials say this, but it is not Know how to achieve it and ensure safety, reliability, and no interference). In the future, the XM8's fire control system is also planned to be compatible with Land Warrior technology.
XM8 no longer uses the M1913 Picatinny rail system, but uses the flat-surfaced hole-shaped Picatinny connection point (PCAP). This diamond-shaped pin connection technology has been patented. This connection method can automatically align, so the XM8's sight can remain zeroed. It only needs to be calibrated and reset by workers before leaving the factory. Then, when the soldier disassembles the sight and then reinstalls it on the rifle, it can still maintain the zero position. Original zero position. There are 14 PCAP points on a basic XM8. In addition to the two PCAP points on the sight base for installing sights, there are 4 PCAP points on both sides and the lower side of the handguard. (There were only 2 on the earliest prototype gun) for installing other accessories. These PCAP points can also be mounted with Picatinny rails, allowing shooters to use M1913 standard interface tactical lights, laser designators, or other accessories on the XM8. The prototype gun below is a new and improved model. It can be found that the two sides of the handguard have two more openings than the prototype gun when it was first announced. Moreover, the four gun types in the concept design are already available in real form.
Although the XM8 is very light, it is a very strong and durable weapon. The receiver is reinforced with a steel plate frame like the G36. The cold-forged barrel has a service life of 20,000 rounds, while the M4 With only 8,000 rounds, the XM8 has a long service life. The high-strength polymer material is very strong and can be produced in different colors. The first-generation prototype gun is available in three types: green suitable for jungle warfare environments, tan for desert environments, and matte black for urban environments. There are plans for more in the future. It is produced in white for polar environments and dark blue for urban environments. Some people even joked that a pink civilian version may be produced in the future, so that politicians who judge the threat of weapons by their appearance can give the green light to the civilian legalization of XM8. However, HK Company's promotional materials state that it has no plans to produce a civilian version of the XM8. Even if the validity period of the 1994 Prohibition of Assault Weapons Law is no longer extended, it will only be provided to law enforcement agencies in the future.
One of the original criticisms of the G36 was that the surface was too smooth, making it difficult to hold the weapon tightly on rainy days. The material surface of XM8 is not only non-slip, but also inlaid with soft rubber polymer on the parts that come into contact with the shooter, such as the lower handguard, cheek piece and shoulder pad, to increase friction and comfort, making it suitable for all weather conditions. weapons used. In addition, the problem of overheating of the handguard that caused headaches for German soldiers on the G36 series has also been solved on the XM8, because the XM8 is a newly designed weapon. The structure of the handguard is different from that of the G36, and heat insulation is added around the hand grip inside the handguard. screen.
The disassembly and assembly of the XM8 are very convenient. You only need to remove two pins to disassemble the rifle. There is one less pin than the G36, and the disassembly and assembly actions are also simplified.
After the disassembly pin is removed, it will be inserted into the two small holes on the carrying handle to prevent loss. This is the same as the G36 disassembly pin is stored on the butt of the gun.
The trigger of the G36 has been criticized by users as being very "stiff", while the trigger of the XM8 is very comfortable and feels obvious when pulled. It can easily fire two or three rounds in full-automatic mode. , and the barrel jump is very small. The sloped cheek piece allows the shooter to find the most suitable cheek position on the gun stock, and can naturally raise his head to aim, without having to aim with an unnatural crooked neck and shoulder position like the G36.
The XM8 can be operated by both hands, and left-handers will also find ways to operate it that is convenient for them. The charging handle is G36 style and is located in the middle of the top of the receiver. The charging handle can be rotated left or right. The magazine catch, empty magazine release button, safety/speed control handle and the elastic button of the telescopic stock can all be operated by both hands. In particular, the magazine catch and empty magazine release button are concentrated in front of the trigger guard, and only need to be used. It can be easily controlled with the index finger of the shooting hand, and it is not easy to operate accidentally. The XM8's short-stock hook release button is very creative. Originally, the short-stock hook handle of the G36 also had a manual hang-up function, but if you want to release the short-stock hook, you have to pull the bolt by hand. The XM8 just extends and bends the protrusion of the manual hang-up. It forms an "L" shape, and can be released from the idle state by just pressing it lightly with the index finger of the shooter's hand. This design does not increase the number of parts and increases the speed of reloading. So whether shooting left-handed or right-handed, shooters don’t have to take their shooting hand off the grip when loading, unloading magazines, switching firing modes or using other controls.
The theoretical rate of fire of the XM8 is 750 rounds/minute, which is similar to other assault weapons. However, due to the small muzzle jump and fast loading speed, the actual rate of fire after firing 210 rounds in a single-shot test can reach an average of 85 rounds/minute, while the average rate of fire of the M4 after firing 210 rounds in a single shot It's 50 rounds/minute. The U.S. Army changed the M16A2 from fully automatic to a three-round burst in the 1980s when office-based experts concluded that most soldiers fired less efficiently in full-auto mode and wasted bullets. However, weapons experts believe that for a well-trained soldier, using three-round burst fire is not more effective than fully automatic shooting. Therefore, the XM8 sample gun only has two shooting modes: single shot and fully automatic shooting. However, HK company’s promotional materials indicate that it can Two- or three-shot burst control devices are produced according to user needs.
The XM8 sample gun uses three types of magazines: 10 rounds, 30 rounds and 100 rounds. The 10 rounds and 30 rounds both use transparent plastic magazines that directly use G36. Two 30-round magazines can be used. Half-moon-shaped connecting points join together. The drum drum is the C-MAG drum produced by the American BETA company for the MG36. The supply reliability of the G36 magazine is better than the M16 standard magazine used by the US military, but it cannot be directly used with the M16 standard magazine. Therefore, if the XM8 is adopted, it is foreseeable that the future XM29 will abandon the M16 standard magazine and switch to the M16 standard magazine. XM8 magazine. However, HK Company has produced a new M16 magazine for HKM4. This magazine is more reliable than the American M16 standard magazine and can be used universally. Therefore, it is not yet certain what kind of magazine the XM8 will use in the future.
The butt of the XM8 is as retractable as the butt of the M4, and the length can be adjusted in 5 positions. After test-firing the XM8 in Las Vegas, some reporters thought that the distance between the shoulder stock and the scope was a little closer. However, due to the relatively mild recoil of the XM8, the scope would not hit the forehead, and many American soldiers would. Wearing a bulletproof vest and other combat gear, so this distance may be just right.
In the description of the early development of OICW, OICW was described as a replacement for the M16 M203 combination. However, during the development process, the Americans have obviously realized that the complex and heavy XM29 cannot completely replace the role of simple and lightweight rifles and ordinary grenade launchers in tactics, so they decided to retain the 40mm grenade crew in the infantry squad in the future.
The 40mm grenade launcher used by the XM8 is no longer the M203 produced by Colt, but an improved AG-C produced by HK Company and named XM320. The loading action of the XM320 is not to push the launch tube forward, but to open it to the left, so longer ammunition, such as the XM1060 dual-purpose grenade under development, can be used. The installation method of the XM320 is also different from that of the M203. It is hung directly under the handguard instead of under the barrel. The combination method is simple and quick, and no special tools are required. In addition, the contractor also plans to allow the XM26 12-gauge light shotgun system under testing to be hung on the XM8. Like the XM320, it can be easily installed or disassembled in the field without the need for special tools.
The XM8 is being tested and improved as it goes. According to a report in Army Times, the U.S. Army is considering adding some type of life monitoring system to each gun. By recording the total number of projectiles, it can Data is obtained on the weapon through an electronic reading device to know the service life of the weapon. The system may also include the ability to record weapons codes in registration files. This new technology will not be difficult. The SP2022 pistol produced by SAUER Company for France has already been implanted with a chip, which has the above functions. In addition, XM8 planners are planning to equip it with a new multi-function bayonet instead of using the existing M9 bayonet.
There are also some suggestions for improvement that hope to integrate some form of remaining ammunition quantity indication, such as using electronic technology to display the remaining ammunition number in the scope, or using mechanical principles to jack up the scope. A small rod so the shooter will know exactly how much ammo is left in the magazine. Although the number of ammunition inside the transparent magazine can be seen at a glance, this requires the shooter to shift his gaze, and the position "hidden" inside the magazine holder cannot be seen.
Second generation
XM8 second generation prototype gun
When the actual combat testing of the XM8 prototype gun in Afghanistan and Iraq is about to be completed, the XM8 Project managers announced the second phase of the XM8 prototype gun, known as the 2nd generation XM8. The soldiers who participated in the test had a good response to the first-generation XM8, but they also made many suggestions for the improvement of XM8, so the second-generation XM8 is the result of gathering feedback from soldiers. The second-generation XM8 was officially submitted to the U.S. Army on May 4, 2004. There are 17 carbines, 15 compacts and 14 precision shooters that will be produced by the weapons research department and the 101st in the fall and winter of 2004. Soldiers from the Airborne Division and the 3rd Infantry Division conduct testing and evaluation. The development progress plan for the XM8 is to complete the actual combat testing of the first-generation prototype gun in the second fiscal quarter of 2004, start the testing of the second-generation prototype gun during the third and fourth quarters of 2004, and conduct the first-generation prototype gun during the first quarter of 2005. The actual combat test of the second generation prototype gun began to be equipped with troops in the late third quarter of 2005. The production was further increased in 2006. The 7.62mm caliber type was tested in the second and third quarters of 2006. The actual combat of the 7.62mm caliber type was carried out in the first quarter of 2007. test.
The improvements of the second-generation XM8 prototype gun are illustrated in the picture below (click on the relevant position in the picture to open a larger image). There are many concepts listed in the design but not implemented on the first-generation prototype gun. items are all added to the second-generation prototype gun. For example, the sighting device on the first-generation prototype gun only has the function of a reflective red dot sight, while the second-generation prototype gun implements other functions of this comprehensive aiming system. , and two aiming devices are provided.
The first type of sight is equivalent to the functional combination of CCO and PEQ-2 used on the M16/M4 system. It is generally used for standard or compact or light machine gun types. The total weight is 272 grams, including A non-magnifying reflex sight with a 1.5 MOA red dot reticle (1.5 inches diameter at 100 yards), an 800 meter range infrared laser designator and a 600 meter range Mi's infrared lighting is powered by a lithium battery.
The second sight is equivalent to the functional combination of ACOG and PEQ-2. It is generally used for precision shooting or light machine gun types. It weighs 567 grams and includes a prism erect image that magnifies 4 times. The sight (same performance as ACOG) can also reflect a 1.5MOA red dot, and also has an infrared laser pointer and infrared illuminator with the same performance as the former.
Another important change regarding the sight is the redesign of the backup sight device. On the first-generation prototype gun, the backup reticle was etched in the sight, while the second-generation prototype gun canceled this reticle and replaced it with a traditional mechanical sight that can be folded and stored on the handguard and handle. Backup sight. On the one hand, the soldiers participating in the test suggested using traditional mechanical sights as backup sights. On the other hand, they also considered that if the photoelectric sight was damaged and could not be aligned, the backup sight would also be unable to be aligned, so an independent backup sight was designed. Tool.
The battery life of the sight has also been increased from 110 hours to 400 hours, and the new design uses a lever clamp instead of screws to fix the sight to the weapon, which is also a response to the soldiers who participated in the test Proposed an easier installation method. In addition, the adjustment of windage and height used to be done with a special small wrench that was easy to lose. Instead, it can be adjusted with a 5.56mm cartridge case or a small coin. In addition, a small and crisp clicking sound can be heard when adjusting windage and height. The control switch of the sight has been moved from the original side position to the back position, making it easier for soldiers to see and operate. The operating area of ??the control switch has also been increased, and the original "up and down" arrows have been replaced with "plus and minus" symbols.
After the disassembly pin is pulled out, it still "hangs" on the mounting hole without having to store it separately, etc. In the design of the first-generation prototype gun, after being removed, the disassembly pin will be inserted into the two small holes on the handle to prevent loss, but in the second-generation sample gun, the disassembly pin will still "hang" after being removed. The mounting hole does not need to be kept separately. This is based on feedback from soldiers who participated in the test, and the same disassembly pin form as the M16/M4 was adopted. In the first generation prototype gun, a telescopic butt that can be folded to the left was produced for compact use. The folding mechanism is the same as that of the G36 butt, but in the opposite direction. A similar design was designed in the second generation prototype gun. MP5 style lever telescopic stock.
In the second generation, the precision shooting type and the light machine gun type were combined into one, except that the light machine gun used a 100-round drum magazine, while the precision shooting type used a standard 30-round magazine. Magazines, of course C-MAG high-capacity drum magazines can also be used on other XM8 models. This decision is because the U.S. Army does not intend to let the XM8 light machine gun replace the M249, which is belt-fed and can quickly change the barrel. Although the modular XM8 can also easily change the barrel, the required process is still too long. long and cannot be used in combat. In addition, the new 20-inch barrel adopts a heavy-duty barrel with longitudinal grooves, which not only reduces weight but also utilizes heat dissipation. In addition, the newly designed bipod can be shortened so that it does not affect the position of the handguard after folding.
On the second-generation prototype gun, the designer increased the theoretical rate of fire from 750 rounds per minute to 850 rounds per minute. The main purpose was to increase the speed of the bolt retraction and make the penetration of the machine easier. The silt in the cartridge is more easily discharged from the gun to improve reliability in desert environments.
The second-generation XM8 also includes some ergonomic improvements, such as the addition of concave and convex grooves on the charging handle for a stronger grip. The hook handle is improved and the bolt release handle is enlarged to make it easier to operate. Improved handguards and increased heat resistance, adding heat shields on the inside of the handguards. Marks are added to the butt so that soldiers can know the extended length of the butt at a glance. The improved shoulder pad makes it easier to aim over the shoulder when wearing body armor. Weight reduction has also been achieved, with the standard model weighing about 1 pound less than the first-generation prototype gun. The standard type originally used the same split-type flash suppressor as the G36K, but the flash suppressors of two sample guns developed cracks after firing 15,000 rounds, so the second generation was changed to similar to the M16 type. birdcage flame suppressor.
The prototype guns are available in black, dark green and khaki, but according to Col. Michael Smith, director of the Project Manager Soldier Weapons office, the final production The model is likely to be an earth-toned digital camouflage, the same as the combat uniform approved by the Army, because camouflage testing found that the black prototype gun exposed the target too easily when moving.
The plan is to first equip two infantry brigades with XM8 in 2005. Although the U.S. Congress canceled the procurement cost of approximately US$27 million in the 2005 budget and supplementary budget, the Army will not give up. With plans to formally equip the XM8 in 2005, the Army is considering digging out money from existing funding. Before these decisions have been finalized, the second-generation XM8 is still scheduled to go to Arizona for desert testing in September, tropical testing in Panama in October, and polar testing in Alaska in December, and is still Experiment and improve as you go.