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Wikipedia
The M4 carbine is a 5.56×45mm NATO, gas-operated, magazine-fed, carbine developed in the United States during the 1980s. It is a shortened version of the M16A2 assault rifle.
The M4 is extensively used by the United States Armed Forces, with decisions to largely replace the M16 rifle in United States Army (starting 2010) and United States Marine Corps (USMC) (starting 2016) combat units as the primary infantry weapon and service rifle. The M4 has been adopted by over 60 countries worldwide, and has been described as “one of the defining firearms of the 21st century”.
Since its adoption in 1994, the M4 has undergone over 90 modifications to improve the weapon’s ergonomics and modularity, including: the M4A1, which strengthened the barrel and removed the burst-fire option; the SOPMOD, an accessory kit containing optical attachments; and the underbarrel M203 grenade launcher.
In April 2022, the U.S. Army selected the SIG MCX SPEAR as the winner of the Next Generation Squad Weapon Program to replace the M16/M4. The rifle is designated XM5.
Following the adoption of the M16 rifle, carbine variants were also adopted for close quarters operations, the first of which was the CAR-15 family of weapons, which served through the Vietnam War. However, these rifles had design issues, as the barrel length was halved to 10 inches (25 cm), which upset the ballistics, reducing its range and accuracy and leading to considerable muzzle flash and blast, meaning that a large flash suppressor had to be fitted.
In 1982, the U.S. Government requested Colt to make a carbine version of the M16A2. At the time, the Colt M16A2 was the Colt 645, also known as the M16A1E1. Later that year, the U.S. Army Armament Munitions Chemical Command helped Colt develop a new variant of the XM177E2, and the U.S. Army redesignated the XM177E2 to the XM4 Carbine, giving the name as the successor to the M3 Carbine. The carbine used the same upper and lower receiver as the M16A1, and fires the M855 cartridge along with the older M193 cartridges. In 1983, the 9th Infantry Division requested a Quick Reaction Program (QRP) for a 5.56mm carbine to replace the M1 Carbine and M3 sub machine gun in service. The XM4 was tested by the Army’s Armament Research and Development Center (ARDC) in June 1983. Later, the gun was updated with improved furniture, and a barrel with rifling of 1 turn in 7 inches (180 mm). The ARDC recommended additional commonality with the M16A2 rifle, as well as lengthening the barrel to 14.5 inches (370 mm). In January 1984, the U.S. Army revised the QRP, and a month later, the Army formally approved development of the new carbine.
In June 1985, the Picatinny Arsenal was given a contract to produce 40 prototypes of the XM4. Initially a joint program between the Army and Marines, in 1986 the Army withdrew their funding. The XM4 was finished in 1987, and the Marines adopted 892 for that fiscal year, with the designation “carbine, 5.56 mm, M4.” Owing to experience from the 1991 Gulf War, the Army gave Colt its first production contracts for M4 carbines in May and July 1993, and M4A1 carbines for SOCOM operators in February 1994.
Interest in the M4 Carbine was accelerated after the Battle of Mogadishu (1993), in which Rangers complained that their M16 rifles were “unwieldy”, whereas members of Delta Force in the same battle, equipped with the CAR-15, had no such complaints. The M4 Carbine first saw action in the hands of U.S. troops deployed to Kosovo in 1999 in support of the NATO-led KFOR peacekeeping force. It would subsequently be used heavily by U.S. forces during the Global War on Terrorism, including in Operation Enduring Freedom and Operation Iraqi Freedom. In the Army, the M4 had largely replaced M16A2s as the primary weapon of forward deployed personnel by 2005. The M4 carbine also replaced most submachine guns and selected handguns in U.S. military service, as it fires more effective rifle ammunition that offers superior stopping power and is better able to penetrate modern body armor.
In 2007, the USMC ordered its officers (up to the rank of Lieutenant Colonel) and staff non-commissioned officers to carry the M4 carbine instead of the M9 handgun. This is in keeping with the Marine Corps doctrine, “Every Marine a rifleman.” The Marine Corps, however, chose the full-sized M16A4 over the M4 as its standard infantry rifle. United States Navy corpsmen E5 and below are also issued M4s instead of the M9. While ordinary riflemen in the Marine Corps were armed with M16A4s, M4s were fielded by troops in positions where a full-length rifle would be too bulky, including vehicle operators, fire team and squad leaders. As of 2013, the U.S. Marine Corps had 80,000 M4 carbines in their inventory.
By July 2015, major Marine Corps commands were endorsing switching to the M4 over the M16A4 as the standard infantry rifle, just as the Army had done. This is because of the carbine’s lighter weight, compact length, and ability to address modern combat situations that happen mostly within close quarters; if a squad needs to engage at longer ranges, the M27 IAR can be used as a designated marksman rifle. Approval of the change would move the M16 to support personnel, while armories already had the 17,000 M4s in the inventory needed to outfit all infantrymen who needed one. In October 2015, Commandant Robert Neller formally approved of making the M4 carbine the primary weapon for all infantry battalions, security forces, and supporting schools in the USMC. The switch was to be completed by September 2016. In December 2017, the Marine Corps revealed a decision to equip every Marine in an infantry squad with the M27, replacing the M4 in that part of the service. MAR SOC will retain the M4, as its shorter barrel is more suited to how they operate in confined spaces.
In 2009, the U.S. Army took complete ownership of the M4 design. This allowed companies other than Colt to compete with their own M4 designs. The Army planned on fielding the last of its M4 requirement in 2010. In October 2009, Army weapons officials proposed a series of changes to the M4 to Congress. Requested changes included an electronic round counter that records the number of shots fired, a heavier barrel, and possibly replacing the Stoner expanding gas system with a gas piston system.
The benefits of these changes, however, have come under scrutiny from both the military and civilian firearms community. According to a PDF detailing the M4 Carbine improvement plans released by PEO Soldier, the direct impingement system would be replaced only after reviews were done comparing the direct impingement system to commercial gas piston operating system to find out and use the best available operating system in the U.S. Army’s improved M4A1.
In September 2010, the Army announced it would buy 12,000 M4A1s from Colt Firearms by the end of 2010, and would order 25,000 more M4A1s by early 2011. The service branch planned to buy 12,000 M4A1 conversion kits in early 2011. In late 2011, the Army bought 65,000 more conversion kits. From there the Army had to decide if it would upgrade all of its M4s. In April 2012, the U.S. Army announced it would begin purchasing over 120,000 M4A1 carbines to start reequipping front line units from the original M4 to the new M4A1 version. The first 24,000 were to be made by Remington Arms Company. Remington was to produce the M4A1s from mid-2013 to mid-2014. After completion of that contract, it was to be between Colt and Remington to produce over 100,000 more M4A1s for the U.S. Army. Because of efforts from Colt to sue the Army to force them not to use Remington to produce M4s, the Army reworked the original solicitation for new M4A1s to avoid legal issues from Colt. On 16 November 2012, Colt’s protest of Remington receiving the M4A1 production contract was dismissed. Instead of the contract being re-awarded to Remington, the Army awarded the contract for 120,000 M4A1 carbines worth $77 million to FN Herstal on 22 February 2013. The order was expected to be completed by 2018.
Replacements for the M4 have mostly focused on two factors: improving its reliability, and its penetration. The first attempt to find a replacement for the M4 came in 1986, with the Advanced Combat Rifle program, in which the case less Heckler & Koch G11 and various flechette rifles were tested, but this was quickly dropped as these designs were mostly prototypes, which demonstrated a lack of reliability. In the 1990s, the Objective Individual Combat Weapon competition was put forth to find a replacement for the M4. Two designs were produced, both by Heckler & Koch: the XM29 OICW, which incorporated a smart grenade launcher, but was canceled in 2004 as it was too heavy, and the XM8, which was canceled in 2005 as it did not offer significant enough improvements over the M4.
The Heckler & Koch HK416 was introduced in 2005, incorporating the same lower receiver as the M4A1, but replacing its direct impingement system with a gas-operated rotating bolt, more comparable to that of the G36. The HK416 was adopted by the Navy SEALs, Delta Force, and other special forces. In 2010, it was adopted by the Marines as the M27 Infantry Automatic Rifle. The same year, the Rangers and Navy SEALs adopted the FN SCAR, but later withdrew their purchase, as it was not a significant enough improvement over the M4A1.
After the failure of the Individual Carbine program, the Next Generation Squad Weapon (NGSW) was started in 2017. The program aimed to replace the M4 Carbine and the M249 SAW with weapons that would compensate for their perceived deficiencies when fighting at longer ranges, as well as addressing concerns about the effectiveness of traditional 5.56x45mm ammunition against troops wearing body armor in a future peer or near-peer conflict. In order to achieve these goals, all weapon submissions were to be chambered in a new 6.8×51 mm caliber.
SIG Sauer, Textron Systems, FN Herstal, True Velocity (previously Lone star Future Weapons and General Dynamics), and PCP Tactical took part in the program. Text ron submitted a cased-telescoped (CT) ammunition-firing rifle for the program; FN Herstal submitted their HAMR IAR re-chambered in 6.8mm caliber; PCP Tactical submitted a modified Desert Tech MDRx; SIG Sauer submitted a redesigned MCX variant known as the MCX-SPEAR. In early 2022, the program concluded, with SIG Sauer being declared the winner. Their rifle entry was designated the XM5, and their automatic rifle the XM250. Operational testing and fielding are scheduled for 2024.
The M4 and its variants fire 5.56×45mm NATO (and .223 Remington) ammunition, and are gas-operated, magazine-fed, selective fire firearms with either a multi-position telescoping stock or a fixed A2 or LE tactical stock. The first stock fitted onto the M4 in 1985 was made entirely of plastic, which only had two positions; fully closed or fully extended. Later models have greater adjust ability, and are commonly known as the “six position stock”, “M4 stock”, or, because of its recesses, “waffle stock”.
The M4 is a shorter and lighter variant of the M16A2 rifle, with 80% parts commonality. The M4’s maneuverability makes it beneficial for non-infantry troops (vehicle crews, clerks and staff officers), as well as for close quarters battle. The M4, along with the M16A4, has mostly replaced the M16A2 in the Army and Marines. The U.S. Air Force, for example, has transitioned completely to the M4 for Security Forces squadrons, while other armed personnel retain the M16A2. The U.S. Navy uses M4A1s for Special Operations and vehicle crews. However, the M4’s shorter barrel reduces its range, with its rear iron sights integrated in the (removable) carry handle only adjustable from 300 m (328 yd) up to 600 m (656 yd), compared to the M16A2 rear iron sights integrated in the fixed carry handle, which can reach up to 800 m (875 yd).
Like all the variants of the M16, the M4 and the M4A1 can be fitted with many accessories, such as night vision devices, flash suppressors, laser sights, telescopic sights, bipods, either the M203 or M320 grenade launcher, the M26 MASS shotgun, forward hand grips, a detachable rail-mounted carrying handle, and anything else compatible with a MIL-STD-1913 picatinny rail.
Other common accessories include the AN/PEQ-2, AN/PEQ-15 multi-mode laser, AN/PEQ-16 Mini Integrated Pointing Illumination Module (MIPIM), M68 CCO, Trijicon TA01 and TA31 Advanced Combat Optical Gunsights (ACOG), EOTech 550 series holographic sights, and Aimpoint M68 Close Combat Optic. Visible and infrared lights of various manufacturers are commonly attached using various mounting methods. As with all versions of the M16, the M4 accepts a blank-firing attachment (BFA) for training purposes.
The M4 and the M4A1 feed from 30-round STANAG magazines. Other types of magazines with different capacities such as the 100 rounds Beta C-Mag are also available. In January 2017, a USMC unit deployed with suppressors mounted to every infantry M4 service weapon. Exercises showed that having all weapons suppressed improved squad communication and surprise during engagements; disadvantages included additional heat and weight, increased maintenance, and the greater cost of equipping so many troops with the attachment. In July 2020, the Marine Corps announced it would be ordering suppressors for use by all M4 carbines used by close combat units. The Marines began to rollout suppressors for all M4/M4A1 carbines in infantry, reconnaissance and special operations units in December 2020.
In 1992, U.S. Special Operations Command (USSOCOM) developed the Special Operations Peculiar Modification (SOPMOD) Block I kit for the carbines used by units operating under its command. The kit features an M4A1, a Rail Interface System (RIS) handguard developed by Knight’s Armament Company (KAC), a shortened quick-detachable M203 grenade launcher and leaf sight, a KAC sound suppressor, a KAC back-up rear sight, an Insight Technologies AN/PEQ-2A visible laser/infrared designator, along with Trijicon’s ACOG TA-01NSN model and Reflex sights, and a night vision sight, among many other accessories. This kit was designed to be configurable (modular) for various missions, and the kit is currently in service with special operations units.
In 2002, the Block II modification kit was adopted featuring two new upper receivers: the Special Purpose Receiver (SPR) and Close Quarter Battle Receiver (CQBR). M4A1s fitted with the SPR were designated by the Navy as the Mk 12 Special Purpose Rifle, a type of designated marksman rifle. M4A1s with the CQBR were designated the Mk 18 Mod 0.
In 2018, the Upper Receiver Group-Improved (URG-I) modification kit was approved for the conversion of Block I and Block II carbine’s upper receiver “to an improved barrel and rail assembly..” which includes the Magpul Industries M-LOK rail interface system.
Variants of the carbine built by different manufacturers are also in service with many other foreign special forces units, such as the Australian Special Air Service Regiment (SASR). While the SASR uses weapons of essentially the same pattern built by Colt for export (Colt uses different models to separate weapons for the U.S. military and those for commercial/export purposes), the British Special Air Service uses a variant on the basic theme, the Colt Canada C8SFW.
Colt Model 925 carbines were tested and fitted with the KAC M4 RAS under the designation M4E2, but this designation appears to have been scrapped in favor of mounting this system to existing carbines without changing the designation. The U.S. Army Field Manual specifies for the Army that adding the Rail Adapter System (RAS) turns the weapon into the M4 MWS or modular weapon system.
The Renault 4, also known as the 4L (pronounced “Quatrelle” in French), is a small economy car produced by the French automaker Renault between 1961 and 1994. Although the Renault 4 was marketed as a short station wagon, its minimal rear overhang, and single top-hinged rear opening made it the world’s first mass-produced hatchback car, as well as the first front-wheel drive family car produced by Renault.
The car was launched at a time when several decades of economic stagnation were giving way to growing prosperity and surging car ownership in France. The first million cars were produced by 1 February 1966, less than four and a half years after launch; eventually over eight million were built, making the Renault 4 a commercial success because of the timing of its introduction and the merits of its design. In early 2020, the 33-year production run of the Renault 4 was counted as the seventeenth most long-lived single generation car in history.
The Renault 4 was Renault’s response to the 1948 Citroën 2CV. Renault was able to review the advantages and disadvantages of the 2CV design. The Citroën had made motoring available to low-income people in France, and especially to farmers and other people in rural areas, for whom the car was as much a working tool as personal transport. The 2CV had been designed in the 1930s for use in the French countryside where the road network was poor – speed was not a requirement but a good ride, useful rough-terrain ability, a versatile body for load carrying, and economy and simplicity of operation were its key considerations. However, by the late 1950s, the 2CV was becoming outdated. Rural roads in France were improved and the national system of auto routes was being developed. Agriculture was becoming more mechanized with fewer smallholdings and family farms for which the 2CV was designed. The Citroën had also proved popular with people living in towns and cities as affordable, economical transport but the 2CV’s rural design brief made it less than ideal as a city car and, despite improvements, the late-1950s 2CV had a top speed of just 70 km/h (43 mph). Its air-cooled two-cylinder engine was reliable and economical but noisy and offered poor performance. The 2CV’s suspension gave it an excellent ride and good grip and handling but was mechanically complex with many moving parts that required regular maintenance and lubrication at intervals as low as every 1000 miles (1600km). With its roots in the 1930s, the 2CV’s styling was also outdated and, with its separate wing/fenders, had a relatively narrow and cramped body for its overall footprint. While the Citroën had been designed during the Great Depression when money was tight and living standards were relatively low, by the 1960s the French economy was growing and people would be able to afford a more modern, refined, and less utilitarian small car.
In early 1956, Renault Chairman Pierre Dreyfus launched this new project: designing a new model to replace the rear engined 4CV and compete against the Citroën 2CV that would become an everyman’s car, capable of satisfying the needs of most consumers. It would be a family car, a woman’s car, a farmer’s car, or a city car.
The Renault 4 shared many design traits with the older Citroën 2CV to allow it to fulfill the same role as a versatile utility car, especially for people in rural France and other parts of the world with poor roads. It had a large structural platform with a separate body. It had front-wheel drive, long-travel fully independent suspension, and Rack and pinion steering. It had a simple body with minimal equipment, a large space for cargo or luggage, and ‘deckchair’ seats which could be easily removed. However, the Renault 4 updated this basic concept with a larger four-cylinder water-cooled engine with a sealed cooling system offering much better refinement and performance than the contemporary 2CV, with a top speed of over 104 km/h (65 mph). The suspension consisted of torsion bars which required no regular maintenance. The boxy full-width body offered more space for both passengers and luggage than the similar-sized 2CV and the car boasted an early hatchback body for greater practicality.
Renault launched the Renault 3 and the Renault 4 simultaneously in July 1961. The cars shared the same body and most mechanical components, but the R3 was powered by a 603 cc version of the engine while the R4 featured a 747 cc engine. This placed the R3 in the 3CV taxation class while the R4 was in the 4CV class. Maximum power output was rated by Renault as 22.5 hp for the R3, and 26.5 or 32 hp for the R4, depending on price level and the type of carburettor fitted. Initially the base versions of the R3 and R4 came with a thick C-pillar behind each of the rear doors. Quarter glass was a 400 francs option for the basic R4. The extra visibility increased the weight of the vehicle, but these windows soon became standard for all R4s.
The R3 and R4 were targeted at the Citroën 2CV that employed soft springs and long wheel travel to absorb bumps on rough roads. The Renault 3/4 applied the same approach and two models appeared at the Paris Motor Show in 1961 on a specialized demonstration display that incorporated an irregular rolling road. Visitors could sit inside a car, which remained undisturbed while the suspension absorbed the erratic bumps of the rolling road. In 1962 Renault employed the same display at the Turin Motor Show.
The basic version of the R3 was priced 40 francs below the lowest-priced version of the Citroën 2CV in 1961 and featured painted bumpers and grille, a simplified instrument panel, a single sun visor, no windshield washer, and no interior door trim panels. This trim was also offered in the more powerful R4. The R4L with six side windows, chrome-colored bumper and grille, as well as a less spartan interior cost 400 francs (roughly 8%) more than the R4 with its four side windows. However, as with the Renault 4CV “Service” in 1953, customers shunned the basic model and in October 1962, the Renault R3 was discontinued, along with the most basic version of the Renault 4.
A “super” version (branded “de luxe” in some export markets) with opening rear quarter-light windows and extra trim was also offered. The de luxe and super versions of the R4L received a version of the engine from the Renault Dauphine giving them an engine capacity of 845 cc. After the withdrawal of the 603 cc engined R3, the 747 cc R4 model continued to be listed with an entry-level recommended retail price, but the slightly larger-engined L versions were more popular. By 1965, Renault had removed the extra “R” from their model names: the Renault R4L had become the Renault 4L.
Early versions of the Renault R4 used engines and transmissions from the Renault 4CV. The original design brief called for an engine size between 600 cc and 700 cc, but there was no consensus as to whether to use a four-cylinder unit or to follow Citroën with a two-cylinder unit. With Volkswagen rapidly growing market share across Europe and North America, Renault also gave serious consideration to an air-cooled boxer motor option for the forthcoming R3/R4. However, using the existing water-cooled unit from the 4CV was a solution, especially in view of the extended period of teething troubles encountered by the Renault Fre gate, which was then Renault’s most recent attempt to develop an innovative powerplant. The existing engines were larger than that specified by management for the new 4CV, but the automaker addressed this by reducing the bore so that the overall capacity of the base engine for the new R3 worked out to be 603 cc, comfortably at the lower end of the required 600–700 cc range. However, since Renault already produced the 747 cc version of the engine that was well proven in the 4CV, it made sense to use this as well in what would in many respects be the older car’s successor. Therefore, in 1961, the R3 had a 49 mm bore and 80 mm stroke, while the R4 received the 54.5 mm × 80 mm existing engine.
Moving the engine from the rear of the 4CV to the front of the new model involved significant planning: design changes to the unit were introduced as part of the process. The inlet manifold was now a steel casting whereas on the 4CV it had been constructed of a light-weight alloy: this was driven by cost considerations now that aluminum was not so inexpensive as it had been fifteen years earlier. Renault also took the opportunity to introduce a feature which subsequently became mainstream. Renault also designed a “sealed-for-life” cooling system, supported by a small expansion tank on the right side of the engine bay. The cooling system contained antifreeze intended to enable operation without topping up or other intervention throughout a car’s life provided ambient temperatures below -40 C were avoided.
The engines were larger than the small 425 cc (later 602 cc and 29 hp), engines in the 2CV. The R4 always had a four-cylinder water cooled engine. The original Renault R4’s engine capacity of 747 cc served to differentiate the model from the more powerful Renault Dauphine, but the Dauphine’s 845 cc engine was used in the 4 itself from 1963 on wards: for most markets at this stage the Dauphine engine now came as standard in the top of the range Renault R4 Super, and was available in some other versions only as an optional extra. Given that Renault’s 603, 747, and 845 cc engines all shared the same cylinder stroke and were all of the same basic design, it is likely that there was very little difference between the manufacturing costs of the basic engine block between the three. From the perspective of the sales and marketing department, they did fall within different taxation classes (respectively 3CV, 4CV, and 5CV) but at this end of the market tax level differences were by now less of an issue even in those European countries that still taxed cars according to engine size.
With time, the increasing trend to the production of Renault 4s in a wide range of countries reduces the validity of generalized statements as to which engines were fitted when: in French-built cars the old 845 cc engine continued in the low versions until the mid-1980s, but in 1978 the top-end Renault 4 GTLs received the new 1108 cc engine: this engine was not new to Renault, however, being the five-bearing “Sierra” engine, first installed in the Estafette van and R8 in the summer of 1962. A smaller version (956 cc) of this new engine finally replaced the by now venerable 845 cc engine in the 4 in 1986. Unlike the original “Billancourt” engine from the 4CV, Renault’s “Sierra” engine rotated in a clockwise direction, so fitting it required reversing the direction of the differential in the gear box in order to avoid producing a car with one forward speed and four reverse speeds.