5.56×45mm NATO

and 5.56×45mm NATO cartridges compared to an AA battery In 1954, the larger 7.62×51mm NATO rifle cartridge was selected as the first standard NATO rifle cartridge. At the time of selection, there had been criticism that the recoil power of the 7.62×51mm NATO, when fired from a handheld lightweight modern service rifle in full automatic mode, did not allow for sufficient control, so the automatic follow-on shots would not hit the intended target but scatter around it. The British had extensive evidence from their own experimentation with intermediate cartridges since 1945, and were on the point of adopting the .280 (7 mm × 43mm) cartridge when the selection of 7.62×51mm (.308) as the NATO standard was made. The FN company had also been involved in the development of the .280 round, including developing a version of the FN FAL in .280. The United States overruled concerns about the recoil and overall effectiveness of 7.62 mm, and the other NATO nations accepted that standardization was more important than the selection of a cartridge that was otherwise ideal. , 7.62×51mm NATO, 7.62×39mm, 5.56×45mm NATO, 5.45×39mm The development of the cartridge that eventually became the .223 Remington (from which 5.56mm NATO would eventually be developed) would be intrinsically linked to the development of a new lightweight combat rifle. The cartridge and rifle were developed as a single unit by Fairchild Industries, Remington Arms, and several engineers working toward a goal set by the U.S. Continental Army Command (CONARC). Early development work began in 1957. A project to create a small-calibre, high-velocity (SCHV) firearm was created. Eugene Stoner of Armalite was invited to scale down the AR-10 (7.62mm) design. Winchester was also invited to participate. Of the cartridges tendered, the .223 Remington (M193) was the basis for a new design created by FN Herstal. The FN-created cartridge was named "5.56×45mm NATO" with a military designation of SS109 in NATO and M855 in the U.S. These new SS109 ball cartridges required a 228 mm (1-in-9 inch) twist rate while adequately stabilizing the longer L110 tracer projectile required an even faster, 178 mm (1-in-7 inch), twist rate. ==Cartridge dimensions==

The 5.56×45mm NATO has a 1.85 mL (28.5 gr H2O) cartridge case capacity. 5.56×45mm NATO maximum NATO cartridge dimensions, all sizes in millimeters (mm) The rifling twist rate for this cartridge is 177.8 mm (1 in 7 in), 6 grooves right-hand twist, Ø lands = , Ø grooves = . STANAG 4172 defines the Belgian ball cartridge SS109 as the NATO reference cartridge and adds a considerable number of technical requirements like a minimum pressure of at the gas port down the long standard proof barrel and primer sensitivity that are not defined by civilian C.I.P. and SAAMI ammunition rulings and recommendations. HPI GP6 Transducer or by equipment to C.I.P. requirements. ==Rifle barrel configurations==

When 5.56×45mm NATO was adopted as standard in 1980, NATO chose a 178 mm (1:7) rifling twist rate for the 5.56×45mm NATO chambering to adequately stabilize the relatively long NATO L110/M856 5.56×45mm NATO tracer projectile. The US at that time converted all rifles in inventory by replacing the barrels and all new US military rifles since have been manufactured with this ratio. In the US, builders of AR-type rifles can specify barrels with either .223 Remington, .223 Wylde, 223 Noveske, or 5.56×45mm NATO chambers in lengths from pistol (7.5") to long rifle (24"). These barrels are also available with rifling ranging from 356 mm (1-in-14") to 178 mm (1-in-7"). US makers are moving toward 5.56×45mm NATO and 178 mm (1-in-7"), which will ensure the least liability. ==Performance==

magazine The 5.56×45mm NATO SS109/M855 cartridge (NATO: SS109; U.S.: M855) with standard 62 gr. lead core bullets with steel penetrator will penetrate about into soft tissue in ideal circumstances. As with all spitzer shaped projectiles, it is prone to yaw in soft tissue. However, at impact velocities above roughly , it may yaw and then fragment at the cannelure (the crimping groove around the cylinder of the bullet). These fragments can disperse through flesh and bone, inflicting additional internal injuries. Fragmentation, if and when it occurs, imparts much greater damage to human tissue than bullet dimensions and velocities would suggest. This fragmentation effect is highly dependent on velocity and therefore on barrel length: short-barreled carbines generate lower muzzle velocity and therefore lose wounding effectiveness at much shorter ranges than longer-barreled rifles. Proponents of the hydrostatic shock theory contend that the shockwave from a high-velocity bullet results in wounding effects beyond the tissue directly crushed and torn by the bullet and fragments. However, others argue that tissue damage from hydrostatic shock is a myth. Critics argue that sonic pressure waves do not cause tissue disruption and that temporary cavity formation is the actual cause of tissue disruption mistakenly attributed to sonic pressure waves. SS109/M855 NATO ball can penetrate up to of steel at 600 meters. According to Nammo, a Finnish-Norwegian ammunition producer, the 5.56×45mm NATO M995 armour piercing cartridge can penetrate up to of RHA steel at 100 meters. The US Army's Ballistic Research Laboratory measured a ballistic coefficient (G7 BC) of 0.151 and form factor (G7 i) of 1.172 for the SS109/M855 ball projectile. The Swedish military has measured the bullet velocities of SS109/M855 military cartridges at from the muzzle fired from differing barrel lengths. Criticism There has been much debate about the bullet's allegedly poor on-target performance regarding stopping power, lethality, and range. Some of this criticism has been used to advocate an intermediate-sized cartridge between the 5.56 and 7.62 NATO sizes while criticisms of poor barrier penetration and accuracy have been used to support the M855A1 EPR round. The shorter barrel of the M4 carbine (with a STANAG 4172 conform 1:7 twist and M855/SS109 5.56 rounds^) generates significantly lower muzzle velocity, reducing the likelihood that the bullet will upset (yaw, fragment, or expand) in the target and resulting in less significant wounds. The 5.56×45mm NATO standard SS109/M855 cartridge was designed for maximum performance when fired from a long barrel, as was the original 5.56 mm M193 cartridge. Experiments with longer length barrels up to resulted in no improvement or a decrease in muzzle velocities for the SS109/M855 cartridge. Shorter barrels produce a greater flash and noise signature, and adding a suppressor to a short-barreled AR family rifle can make it unreliable, as the reduced time for the propellant to burn in the barrel and the higher muzzle pressure at the suppressor entrance can cause faster cycling and feeding issues. Unless the gas port can be regulated or adjusted to higher pressures, suppressors for short-barreled 5.56×45mm NATO firearms must be larger and heavier than models for standard-length rifles to function reliably. SS109/M855 cartridges fired from barrels under about in length do not have enough muzzle velocity energy to cause extreme damage that occurs only at terminal velocities of over on impact, reducing the wounding capacity. Compared to larger calibers, proponents of the 5.56×45mm NATO round contend that animal studies of the wounding effects of the 5.56×45mm NATO round versus the 7.62×39mm have found that the 5.56×45mm NATO round is more damaging, due to the post-impact behavior of the 5.56 mm projectile resulting in greater cavitation of soft tissues. The US Army contended in 2003 that the lack of close-range lethality of the 5.56×45mm NATO was more a matter of perception than fact. With controlled pairs and good shot placement to the head and chest, the target was usually defeated without issue. The majority of failures were due to hitting the target in non-vital areas, such as the extremities. However, a minority of failures occurred despite multiple chest hits. Some have contended that shot placement is the most important factor in determining a bullet's lethality. Difficulty with the 5.56×45mm NATO at long ranges has been attributed to training; Swedish ISAF units relied on .50 BMG heavy machine guns for long-range shooting due to resilience to factors such as range and wind drift. Underperformance is thus attributed to errors in range and wind estimation, target lead, firing position, and stress under fire, all of which can be resolved through training. Originally designed for use in the Mk 12 SPR, the ammunition has found favor with special forces units who were seeking a more effective cartridge to fire from their M4A1 carbines. Commercially available loadings with these heavier (and longer) bullets can be prohibitively expensive, costing much more than military surplus ammunition. Additionally, these heavy-for-caliber loadings sacrifice some penetrative ability compared to the M855 round (which has a steel penetrator tip). The performance of 5.56×45mm military ammunition can generally be categorized as almost entirely dependent on velocity to wound effectively. Heavy OTM bullets enhance soft tissue wounding ability at the expense of hard-target/barrier penetration. U.S. Special Forces had sought to create a round that had increased power out of carbine M4 barrels and compact SCAR-L barrels, while increasing hard target performance. Developmental efforts led to the creation of the Mk318. The bullet uses an open-tip design to inflict damage on soft tissue and has a brass rear to penetrate hard targets. The tip and lead core fragments consistently, even when using short barrels, while the rear moves through once the front impacts. It has more consistent performance because it is not yaw-dependent like the M855; the nose fragments upon impact and solid rear penetrator continues to move relatively straight. This makes the Mk318 effective against personnel with or without body armor. The round also increases accuracy, from 3–5 minute of angle (MOA) with the M855 from an M4A1 barrel to 1.71 MOA at 300 yards and 1.67 MOA at 600 yards from a SCAR-L barrel. For general issues, the U.S. Army adopted the M855A1 round in 2010 to replace the M855. The primary reason was pressure to use non-lead bullets. The lead slug is replaced by a copper alloy slug in a reverse-drawn jacket, with a hardened steel penetrator extending beyond the jacket, reducing lead contamination to the environment. The M855A1 offers several improvements other than being lead-free. It is slightly more accurate, has better consistency in its effect on wounding ability, and has increased penetrating capability. The 62-grain (4.0 g) projectile can better penetrate steel, brick, concrete, and masonry walls, as well as body armor and sheet metal. It penetrates of mild steel at 350 meters, which the M855 can only do at 160 meters. The propellant burns faster, which decreases the muzzle flash and gives a higher muzzle velocity, an important feature when fired from a short-barreled M4 carbine. Although the M855A1 is more expensive to produce, its performance is considered to make up for it. One possible danger is that it generates much greater pressure in the chamber upon firing, reducing the service life of parts and increasing the risk of catastrophic failure of the weapon (though this has yet to occur). The U.S. Marines adopted the Mk318 in early 2010 due to delays with the M855A1. This was a temporary measure until the M855A1 was available to them, which occurred in mid-2010, when the Army began receiving the rounds. Both the Mk318 and M855A1 weigh the same, have similar performance, and outperform the M855 against all targets. SOCOM spent less money developing the Mk318, and it is marginally better than the M855A1 in some situations, but costs more per round. The Army spent more developing the M855A1, which performs as well or nearly as well as the Mk318 but is cheaper per round and is lead-free. While SOCOM constantly seeks better equipment, the Army and Marines have far more troops to supply and buy more ammunition than SOCOM does. Alternatives If the 5.56 mm bullet is moving too slowly to reliably yaw, expand, or fragment on impact, the wound size and potential to incapacitate a person are greatly reduced. There have been numerous attempts to create an intermediate cartridge that addresses the complaints about 5.56 NATO's lack of stopping power, as well as the lack of controllability seen in rifles firing 7.62 NATO in full auto. Some alternative cartridges, such as the 300 AAC Blackout (7.62×35mm), prioritize penetration and stopping power at short ranges by sacrificing long-range performance. These calibers are designed to be interoperable with 5.56 by maintaining similar dimensions, allowing them to be used in a 5.56-chambered rifle with a simple barrel change. By late 2004, the 6.8mm Remington SPC (6.8×43mm) was in limited use with U.S. Special Operators. In 2007, both the U.S. SOCOM and the U.S. Marine Corps decided not to field weapons chambered in 6.8×43mm due to logistical and cost issues. In April 2022, the U.S. Army selected a new rifle and light machine gun as part of the Next Generation Squad Weapon Program. They will replace 5.56 mm weapons, being chambered in 6.8×51mm Fury that has greater accuracy and range while being more lethal than 5.56×45mm NATO and 7.62×51mm NATO against emerging threats. ==5.56mm NATO versus .223 Remington==

The exterior dimensions of the 5.56mm NATO and .223 Remington cartridges are identical. While the cartridges are identical other than powder load, the chamber leade, i.e., the area where the rifling begins, is cut to a sharper angle on some .223 commercial chambers. Because of this, a cartridge loaded to generate 5.56mm pressures in a 5.56mm chamber may develop pressures that exceed SAAMI limits when fired from a short-leade .223 Remington chamber. As the chambers differ, the head space gauges used for the two chamberings differ. Brass case The dimensional specifications of 5.56 NATO and .223 commercial brass cases are identical. The cases tend to have similar case capacities when measured, with variations chiefly due to brand, not to the 5.56 vs .223 designation. The result is that there is no such thing as "5.56 brass" or ".223 brass"; the differences between the cartridges lie in pressure ratings and chamber length, not in the shape or thickness of the brass. In July 2012, the US Army requested vendors to supply alternative cartridge cases to reduce the weight of an M855A1 5.56 mm round by at least 10 percent, as well as for the 7.62 NATO and .50 BMG rounds. The cartridge cases must meet all performance requirements when fully assembled, be usable by the Lake City Army Ammunition Plant, and be manufactured in quantities totaling approximately 45 million per year. Polymer-cased ammunition is expected as a likely lightweight case technology. A hybrid polymer/metal version of a conventional cartridge case would be thicker than regular cases and reduce the amount of space for the propellant, although certain polymers could be thermodynamically more efficient and not lose energy to the case or chamber when fired. Pressure The pressure limits for .223 Rem and 5.56×45mm NATO are very similar, fired in their respectively designed chambers, if using similar measurement methodologies. Chamber pressures obtained using different methods are not comparable. • The SAAMI sets the pressure limit for .223 Rem at , using a chamber-conformal piston transducer. The US military uses a similar methodology (SCATP) and produced a very similar limit for their ammunition, at , in the 1970s–80s. Early versions of NATO standards quote a very similar number. • On the other hand, Bryce Towsley quotes Jeff Hoffman from Black Hill Ammunition as saying that military cartridges can yield peak pressures in excess of in the SAAMI setup. • NATO EPVAT testing uses case-mouth transducer pressure. • The 2005 proof pressure for 5.56×45mm NATO is , which, when divided by a factor of 1.25, yields the same maximum service pressure of . • It is the current latest (2020) NATO AEP-97/AOP-4172 pressure testing method. NATO no longer gives a limit on the mean pressure, only a "mean + 3 standard deviations" limit of . The "NATO Reference Ammunition" from the same publication has a mean pressure of . Chamber The 5.56mm NATO chamber, known as a NATO or mil-spec chamber, has a longer leade, the distance between the mouth of the cartridge and the point where the rifling engages the bullet. The .223 Remington chamber, known as the SAAMI chamber, is allowed to have a shorter leade and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Rock River Arms) or the ArmaLite chamber, which are designed to handle both 5.56×45mm NATO and .223 Remington equally well. The leade of the .223 Remington minimum C.I.P. chamber also differs from the 5.56mm NATO chamber specification. The casings and chambers for .223 Remington and 5.56×45mm NATO are virtually the same dimensions. Still, because .223 Remington is designed to handle much lower pressures than 5.56×45mm NATO, the rounds are not completely interchangeable. Firing a 5.56×45mm NATO round out of a rifle chambered in .223 Remington could be injurious or fatal to the user as well as the gun, however .223 Remington ammunition can be fired safely from almost any rifle chambered in 5.56×45mm NATO as the NATO specified rifles can handle much higher chamber pressures than the .223 Remington is capable of producing. Using commercial .223 Remington cartridges in a 5.56mm NATO-chambered rifle should work reliably, but until recently it was believed that it was less accurate than when fired from a .223 Remington-chambered gun due to the longer leade. Although that may have been true in the early 1960s when the two rounds were developed, recent testing has shown that rifles chambered in 5.56×45mm NATO can also fire .223 ammunition every bit as accurately as rifles chambered in .223 Remington, and the 5.56×45mm NATO chamber has the additional advantage of being able to fire both calibers safely. Using 5.56×45mm NATO mil-spec cartridges (such as M855) in a .223 Remington-chambered rifle can lead to excessive wear and stress on the rifle and may even be unsafe, and SAAMI recommends against the practice. (More recent tests have failed to find any "dangerous pressure spike" when firing military ammunition in a .223 chamber.) Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56×45mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14 (marked ".223 cal", except the Mini-14 "Target" model, which only fires .223), but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56×45mm NATO ammunition. The upper receiver (to which the barrel with its chamber is attached) and the lower receiver are entirely separate parts in AR-15 style rifles. If the lower receiver has either .223 or 5.56 stamped on it, it does not guarantee the upper assembly is rated for the same caliber, because the upper and the lower receiver in the same rifle can, and frequently do, come from different manufacturers, particularly with rifles sold to civilians or second-hand rifles that have been repaired with spare parts. Since all parts are interchangeable, a shooter must take great caution to check for markings of 5.56×45mm on the barrel before attempting to fire 5.56×45mm NATO ammunition out of it. In more practical terms, most AR-15 parts suppliers engineer their complete upper assemblies (not to be confused with stripped uppers where the barrel is not included) to support both calibers to satisfy market demand and prevent any potential problems. Some manufacturers have begun offering a hybrid .223 Wylde chamber designed to support both cartridges optimally. ==Ammunition capacity for weight comparison==

The first confrontations between the 7.62×39mm chambered AK-47 and the 7.62×51mm NATO cartridge M14 rifle came in the early part of the Vietnam War. Battlefield reports indicated that the M14 was uncontrollable in full-auto and that soldiers could not carry enough ammo to maintain fire superiority over the AK-47. A replacement was needed; as a result, the Army was forced to reconsider a 1957 request by General Willard G. Wyman, commander of the U.S. Continental Army Command (CONARC) to develop a .223 caliber (5.56 mm) select-fire rifle weighing 6 lbs (2.7 kg) when loaded with a 20-round magazine. This request ultimately led to the development of a scaled-down version of the Armalite AR-10, called the ArmaLite AR-15 rifle. During testing it was found that a 5- to 7-man team armed with ArmaLite AR-15s had the same firepower as an 11-man team armed with M14s. Also, soldiers armed with ArmaLite AR-15s could carry nearly three times more ammunition as those armed with M14s (649 rounds vs 220 rounds). The ArmaLite AR-15, officially designated Rifle, caliber 5.56 mm, M16, was later adopted by U.S. infantry forces as the standard-issue rifle. The following table compares the maximum ammunition load a fire team can carry to support five similar rifles (measured in box magazines of ): ==5.56mm NATO versus 7.62mm NATO==

, 5.56mm NATO and 9mm Parabellum Hit probability refers to the ability of a soldier to concentrate on firing despite their weapon's recoil and noise, which is noticeably different between the two cartridges. The 7.62 NATO has twice the impact energy of the 5.56 NATO, preferable if a target is protected by higher-level armor, especially at "medium" range. If not, both rounds normally penetrate satisfactorily through enemies up to approximately 600 meters. A 5.56 NATO round fired from a barrel has a flatter trajectory than a 7.62 NATO round fired from a barrel of equal length, while the 5.56 NATO fired from a barrel has the same trajectory as the 7.62 NATO from a 20 in barrel, as well as the same time of flight. A 7.62 NATO round reaches 50 percent of its velocity within of the barrel when fired, so decreasing the barrel length for close quarters combat results in increased muzzle pressure and greater noise and muzzle flash. ==Military cartridges==

Australia Packaging configurations for M2A1-type ammunition boxes include 1,080 loose rounds, 900 rounds divided across eighteen plastic film packs containing fifty rounds each, 600 rounds in bandoliers containing 15-round charger clips, and 800 linked rounds divided across four 200-round belts each which can contain either a single ammunition nature or a mix of ammunition natures (e.g. four ball rounds followed by one tracer round). Unless stated otherwise, all ammunition listed below is produced by Thales Australia. Since 2012, Thales Australia's ammunition production has been conducted via its Australian Munitions subsidiary. • Cartridge, Ball, F1 (1985–present): Unlike the F1 cartridge, the F1A1 headstamp has a dimple at 3 o'clock and 9 o'clock. This is a hallmark of the automated SCAMP loading machinery used to make the new cartridges. • Cartridge, Ball, F193: Belgium • Cartridge, Ball, SS109: 5.56×45mm semi-armor-piercing cartridge with steel penetrator produced by Fabrique Nationale. Adopted in 1979 as the NATO standard. • Cartridge, Tracer, C78: 5.56×45mm FN SS110 equivalent used in the C7, C8 and C9 type weapons. Made by General Dynamics Canada. • Cartridge, Blank, C79 [Crimped tip]: 5.56×45mm blank cartridge used in the C7, C8 and C9 type weapons. Also made by General Dynamics Canada. France Ammunition made by GIAT. • 'Type O (Ordinaire, "Standard" or "Ball"):' A full-metal-jacketed lead-core bullet similar to the US M193. It was used with the FAMAS. • 'Type T (Traçant, "Tracer"):' A tracer bullet similar to the US M196. Germany • Patrone AA59, 5.56×45mm, DM11, ("Soft-core", or Ball) [Green tip]: 5.56×45mm 4.1 g dual core ball cartridge with steel core, similar to M855/SS109, produced by RUAG Ammotec. • Patrone, 5.56×45mm, DM11 A1, [Green tip]: 5.56×45mm dual core ball cartridge with steel core, similar to M855/SS109, designed for and used by the German Bundeswehr with NATO approval (AC/225-125A), produced by Metallwerk Elisenhütte GmbH. • Patrone, 5.56×45mm, DM18, ("Maneuver"): Blanks with brass base, produced by Metallwerk Elisenhütte GmbH. • Cartridge, Ball, Type 89(C) • Cartridge, Ball, Type 89(C), Linked • J3 : 5.56×45mm bullet, weight 12 grams, made from steel and red brass, and uses a double-base powder, specifically made for Japan's new Type 20 rifle, which will replace the Type 89 rifle in Japan Ground Self Defence Force service. South Africa Packaging configurations for all ammunition natures consisted of a plastic 8217 box containing 2,700 rounds, divided across nine PVC bags of ten thirty-round cartons each, and a conventional M2A1 box containing 800 rounds, divided across forty twenty-round cartons each. For linked ammunition, configurations consisted of a plastic 7716 box containing 2,000 linked rounds, divided among five plastic 7815 cases of two 200-round belts each, and a conventional M2A1 box containing 800 linked rounds, divided among four 200-round belts each. Unless stated otherwise, all ammunition listed was or is produced by Pretoria Metal Pressings, which became a division of Denel upon the latter's formation in 1992. • Round, 5.56×45mm, Ball, R1M1/M2: M193 equivalent with Boxer (R1M1) or Berdan (R1M2) primers produced from 1977 to 1983. • Round, 5.56×45mm, Tracer, R1M1/M2: M196 equivalent produced from 1979 to 1983. • Round, 5.56×45mm, Tracer, M2A2/A3/A4: M196 equivalent produced from 1983 onwards. or 900 rounds, with these containing either cardboard cartons of twenty rounds each, cardboard cartons of thirty rounds each (900-round H83s only), or nylon bandoliers with five pockets containing three ten-round charger clips each for a total of 150 rounds per bandolier (900-round H83s only). In addition to these H83 configurations, blank rounds can come in wire-bound wooden boxes containing 1,000 rounds in twenty-round cartons. Linked ammunition is supplied in H83 boxes that contain belts of the desired quantity and link configuration (e.g. a 800-round box consisting of belts arranged in a sequence of four ball rounds followed by one tracer round). • Round, 5.56mm Ball, M193: M193 equivalent produced by Radway Green (though some quantities of Hirtenberger Patronen-produced rounds were imported) • Round, 5.56mm Ball, L2A1/A2: FN SS109 equivalent produced by Radway Green. • Round, 5.56mm Ball, L3A1: M193 equivalent produced by Hirtenberger Patronen for use in AR-15 weapons and the HK 53 (L101A1/A2) rifle. • Round, 5.56mm Ball, L7A1: Produced by Hirtenberger Patronen • Round, 5.56mm Tracer, L1A1/A2 [Red tip]: Tracer round complement to L2A1/A2, produced by Radway Green. 1,140 rounds of blank ammunition in cartons, and 800 linked rounds irrespective of ammunition natures. Typical wire-bound wooden box capacities include 1,680 rounds and 1,600 rounds. US Army • Cartridge, Caliber 5.56 mm, Ball, M193: 5.56×45mm ball cartridge. This was type-standardized and designated by the US Army in September 1963. • Cartridge, Caliber 5.56 mm, Grenade, M195 [Crimped tip with Red lacquer seal]: 5.56×45mm high-pressure grenade-launching blank. • Cartridge, Caliber 5.56 mm, Tracer, M196 [Red or Orange tip]: 5.56×45mm tracer cartridge. • Cartridge, Caliber 5.56 mm, High Pressure Test (HPT), M197 [stannic-stained or nickel-plated case]: High-pressure Testing cartridge used when proofing weapons during manufacture, test, or repair. • Cartridge, Caliber 5.56 mm, Dummy, M199 [No primer, Fluted case]: 5.56×45mm inert cartridge with fluted indentations in the case. Used for loading and unloading drills during basic training. • Cartridge, Caliber 5.56 mm, Blank, M200 [Crimped tip with Violet lacquer seal]: 5.56×45mm training blank cartridge. • Cartridge, Caliber 5.56 mm, Ball, M202: 5.56×45mm FN SSX822 cartridge. • Cartridge, Caliber 5.56 mm, Dummy, M232 [No primer, Black-anodized case and bullet]: 5.56×45mm inert cartridge. Used for testing rifle mechanisms. • Cartridge, Caliber 5.56 mm, Ball, XM287: 5.56×45mm ball cartridge produced by Industries Valcartier, Inc. An Improved version was also produced designated XM779. • Cartridge, Caliber 5.56 mm, Tracer, XM288: 5.56×45mm tracer cartridge produced by Industries Valcartier, Inc. An Improved version was also produced designated XM780. • Cartridge, Caliber 5.56 mm, Grenade, M755 [Crimped tip with Yellow lacquer seal]: 5.56×45mm grenade launching blank specifically for the 64mm M234 launcher. The original white lacquer seal was discontinued due to excessive bore fouling. Its design is otherwise an exact duplicate of the M195 Grenade cartridge. • Cartridge, Caliber 5.56 mm, Ball, XM777: 5.56×45mm ball cartridge. An attempt to create a 55-grain SS109-style semi-armor-piercing round that weighed the same as the M193 and could use the same US-standard 1-in-12-inch rifling. It replaced the 6×45mm SAW round as the baseline cartridge for the Squad Automatic Weapon trials in the late 1970s and early 1980s. • Cartridge, Caliber 5.56 mm, Tracer, XM778: 5.56×45mm tracer cartridge mated with the XM777 Semi-Armor-Piercing cartridge. • Cartridge, Caliber 5.56 mm, Ball, M855 [Green tip]: 5.56×45mm 62-grain FN SS109-equivalent ball cartridge with a steel penetrator tip over a lead core in a full copper jacket. It is designed to penetrate lightly armored targets, such as body armor or light vehicles, and has a steel core that provides increased penetration. • 'Cartridge, Caliber 5.56 mm, Ball, M855LF Lead Free [Green tip]': bullet with a steel penetrator tip over a tungsten-composite core in a full copper jacket. Primarily used during training in countries with strict lead disposal laws. • 'Cartridge, Caliber 5.56 mm, Ball, M855A1 Enhanced Performance Round [unpainted steel penetrator tip]' (2010–present): bullet with a steel penetrator tip over a copper alloy core in a partial copper jacket. • Cartridge, Caliber 5.56 mm, Tracer, M856 [Orange tip]: 5.56×45mm FN L110 tracer cartridge. Provides red visible light and lacks a steel penetrator. • Cartridge, Caliber 5.56 mm, Tracer, M856A1 [Red tip]: 5.56×45mm 56-grain Lead Free slug (LF) Tracer with similar ballistic performance to the M855A1 and improved visible trace to range consistency. • Cartridge, Caliber 5.56 mm, Plastic, Practice, M862 [Brass primer, Aluminum case and Blue plastic projectile]: Short Range Training Ammo (SRTA) uses a light plastic bullet with a maximum range of just 250 meters. Because the M862 has less energy, the M2 training bolt must be used in the M16 Rifle / M4 Carbine for the weapon to cycle properly. The M2 training bolt and M862 cartridge case use a smaller-than-standard head diameter as a safety feature, preventing standard ammunition from being chambered or fired. The M862 SRTA is typically used for training on small, limited-size shooting ranges, such as near built-up or populated areas. • Cartridge, Caliber 5.56 mm, Armor Piercing, M995 [Black tip]: 5.56×45mm AP cartridge with a tungsten core. • Cartridge, Caliber 5.56 mm, Tracer, XM996 [Crimson tip]: So-called "Dim Tracer" with reduced effect primarily for use with night vision devices. US Air Force • Cartridge, Caliber 5.64 mm, Ball, MLU-26/P (Munition, Live, Unit #26 / Personnel use) (Federal Stock Number (FSN): 1305-968-5892, DOD Identification Code (DODIC): A066; assigned 1 January 1962): Early USAF designation for a 5.56×45mm FMJ Boat-Tailed ball cartridge produced by Remington-Union Metallic Cartridge Company. It was their designation for the commercial 55-grain .223 Remington M.C. ("Metallic-Cased", or Full Metal Jacketed) cartridge, which the Air Force initially designated "5.64 mm" (.222 caliber) rather than 5.56 mm (.218 caliber). The first order in 1963 (headstamped RA 63 or REM-UMC 63) consisted of 8.5 million rounds and was procured for testing, training, and unconventional warfare use with the XM16 rifle. The cartridges came packed unclipped in white 20-round commercial ammunition cartons, packed 36 cartons (720 rounds) per M2A1 ammo can, and shipped two M2A1 cans (1440 rounds in total) per wire-bound plywood crate. Until the Army adopted the M193 Ball round, this was the only type of military 5.56mm ammunition available in the Southeast Asia theater. US Navy and US Marine Corps • Cartridge, Caliber 5.56 mm, Frangible, MK 255 MOD 0 [White Tip]: 5.56×45mm Reduced Ricochet Limited Penetration (RRLP) round with copper/polymer composite core for training and operational use. • Cartridge, Caliber 5.56 mm, Special Ball, Long Range, Mk 262 MOD 0/1: 5.56×45mm open-tipped match/hollow-point boat-tail cartridge. MOD 0 features a Sierra MatchKing bullet, while MOD 1 features either a Nosler or a Sierra bullet. • Cartridge, 5.56×45mm, semi-jacketed Frangible, MK 311 MOD 0 : Reduced Ricochet Limited Penetration (R2LP) round, frangible bullet intended for training. Produced by Western Cartridge Company (headstamp: WCC). • Cartridge, Caliber 5.56 mm Ball, Enhanced 5.56 mm Carbine, MK 318 MOD 0: 5.56×45mm Open-Tipped Match Boat-Tail cartridge. Optimized for use with 14-inch barreled weapons like the M4A1 Carbine and MK 16 SCAR and designed to penetrate light barriers like windshields or car doors with no loss of accuracy or damage. Since designated as Caliber 5.56 mm Ball, Carbine, Barrier. SS109/M855 In 1970, NATO decided to standardize a second rifle caliber. Tests were conducted from 1977 to 1980 using U.S. XM777 5.56 mm, Belgian SS109 5.56 mm, British 4.85×49mm, and German 4.7×33mm caseless. No weapon could be agreed upon, as many were prototypes, but the SS109 was found to be the best round and standardized on 28 October 1980. The SS109 was developed in the 1970s for the FN FNC rifle and the FN Minimi machine gun. To increase the Minimi's range, the round was designed to penetrate 3.5 mm of steel at 600 meters. The SS109 had a steel tip and lead rear and was not required to penetrate body armor. Barrels required at least a 1:9 in rifle twist, but needed a 1:7 in rifle twist to fire tracer ammunition. The M855 is yaw dependent, meaning it depends on the angle at which it hits the target. If at a good angle, the round turns as it enters soft tissue, breaking apart and transferring its energy to what it hits. If impacting at a bad angle, it could pass through without transferring its full energy. In Afghanistan, troops found that M855 rounds also suffered at long ranges. Although 5.56 mm rifles have an effective range of 450–600 meters, the M855 bullet's performance falls off sharply beyond 300 meters. The ranges are even shorter for short-barreled carbines. Half of small-arms attacks were launched from 300 to 900 meter ranges. An M855 fired from an M4 carbine has severely degraded performance beyond 150 meters. M855A1 The M855A1 Enhanced Performance Round (EPR) was introduced in June 2010. It features a lead-free projectile with a solid copper core, and is tailored for use in rifles with shorter barrels such as the M4 carbine. It provides more consistent performance compared to the M855. It is not necessarily more lethal than the SS109/M855, but performs more consistently every time it hits a soft target and retains its performance at longer distances. The EPR can penetrate a thick mild steel barrier from an M4 at and from an M16 at . Compared to the SS109/M855 the M855A1 muzzle velocities are somewhat increased to (+) for the M16 and (+) for the M4 carbine. The M855A1 bullet has a greater length than the SS109/M855. Because steel and copper are less dense than lead, the bullet is lengthened inside the case to achieve the same weight as its predecessor. While effectiveness at different ranges is increased, the M855A1 does not increase the effective ranges at which weapons are expected to hit their targets. The Enhanced Performance Round was made to nearly match the trajectory of the M855 to aid in training consistency—the SS109/M855 ballistic coefficient (G7 BC) of 0.151 was improved to 0.152 for the M855A1—but the ranges to get desired effects are greatly extended. The United States Marine Corps purchased 1.8 million rounds in 2010, with plans to adopt the round to replace the interim MK318 SOST rounds used in Afghanistan when the M855A1 project was delayed. The Marine Corps plans to adopt the M855A1 round in 2018; although testing revealed it caused "some durability issues" with the Marines' M27 Infantry Automatic Rifle, the weapon is still "operationally suitable" when firing the round. On a media day at Aberdeen Proving Ground on 4 May 2011, reports were given about the M855A1's performance in the field since it was issued 11 months earlier. One primary advantage given by the round is its consistent performance against soft targets. While the older SS109/M855 was yaw-dependent, which means its effectiveness depends on its yaw angle when it hits a target, the M855A1 delivers the same effectiveness in a soft target, no matter its yaw angle. The new SMP-842 propellant in the round burns quicker in the shorter M4 carbine barrel, ensuring less muzzle flash and greater muzzle velocity. The M855A1 was able to penetrate of mild steel plate at . The round even penetrated concrete masonry units, similar to cinder blocks, at from an M16 and at from an M4, which the M855 could not do at those ranges. Its accuracy is maintained and sometimes increased, as it was able to shoot a group better at . In February 2011, the M855A1 was used more than the M855, and approximately 30 million M855A1 rounds were fielded from June 2010 to May 2011. The M855A1 was put to the test at the 2012 National Rifle Association's National High-Power Rifle Championship at Camp Perry, Ohio, in August 2012. The shooter for the Army was Rob Harbison, a contractor supporting small caliber ammunition capability development at Fort Benning Georgia. This was a special event for the Project Manager for Maneuver Ammunition Systems and the Army's Maneuver Center of Excellence, as it was an opportunity to showcase the Enhanced Performance Round's capabilities. With an M16 loaded with M855A1 ammo, Harbison fired a perfect 200 points in the Coast Guard Trophy Match, which is 20 shots fired from the sitting position at 200 yards, finishing 17th out of 365 competitors. He also scored a perfect 100 on the final string of ten shots during the Air Force Cup Trophy Match, fired at 600 yards from the prone position, which is 10 shots in a row within the 12-inch, 10-point ring at 600 yards with combat ammunition. Harbison was happy with the EPR's performance, with his scores showing that the Army's newest general-purpose round is accurate enough to go toe-to-toe with the best ammo available, whether bought or hand-loaded. Harbison even said, "I don't think I could have scored any higher if I [were] using match-grade competition ammunition." The M855A1 was not fired from 1:7 in rifled barrels used in standard Army rifles, but special Army Marksmanship Unit (AMU) match-grade 1:8 in rifled barrels, which produce more accurate results when firing 62-grain rounds. Since its introduction, the M855A1 has been criticized for its St. Mark's SMP842 (former WC842) ball propellant, which has been shown to increase fouling of the gun barrel. Post-combat surveys have reported no issues with the EPR in combat. A series of tests found no significant difference in fouling between the old M855 and the M855A1. However, manufacturers have reported "severe degradation" of barrels in rifles using the M855A1 in tests. The Army attributes pressure and wear issues with the M855A1 to problems with the primer, which they claim to have addressed with a newly designed primer. It uses a modified four-pronged primer anvil for more reliable powder ignition, During Army carbine testing, the round caused "accelerated bolt wear" from higher chamber pressure and increased bore temperatures. Special Operator testing saw cracks appear on locking lugs and bolts at cam pin holes on average at 6,000 rounds, but sometimes as few as 3,000 rounds during intense automatic firing. Firing several thousand rounds at such high chamber pressures can degrade accuracy over time as parts wear out; these effects can be mitigated by using a round counter to track part service life. Weapons with barrel lengths shorter than the M4 firing the M855A1 also experience 50 percent higher pressures than a full-length M16 rifle barrel, which can cause port erosion that can boost the automatic fire rate, increasing the likelihood of jams. An independent 2024 study concludes the M855A1 chamber and port pressures were measured to be significantly over the relevant NATO standard – to which all 5.56×45mm NATO arms are designed for – in M16 and M4 small arms, causing problems in these ammunition specific "internal piston" system and the M27 IAR "external piston" system small arms platforms. Mk 262 The Mk 262 is a match-quality round manufactured by Black Hills Ammunition made originally for the Special Purpose Rifle (SPR). It uses a Sierra MatchKing bullet that is more effective at longer ranges than the standard issue M855 round. In 1999, SOCOM requested Black Hills Ammunition to develop ammunition for the Mk 12 SPR that SOCOM was designing. For the rifle to be accurate out to 700 yards, Black Hills "militarized" a cartridge that used the Sierra OTM (Open Tip Match) projectile; it switched from a .223 Remington to 5.56 mm case, increased pressure loading, crimped and sealed the primer, and added a flash retardant to the powder. The Mk 262 MOD 0 was adopted in 2002. Issues came up in development, including reliability problems at different temperatures and when the weapon got dirty, and cycling issues in cold weather due to the slightly shorter SPR barrel compared to the full-length M16A2 barrel. The problems were addressed by using a slower-burning powder with a different pressure in the barrel, resulting in the Mk 262 MOD 1 in 2003. During the product improvement stage, the new propellant was found to be more heat-sensitive in weapon chambers during rapid firings, resulting in higher pressures and failure to extract. This was addressed with another powder blend with higher heat tolerance and improved brass. Also during the stage, Black Hills wanted the bullet to be given a cannelure, which had been previously rejected for fear it would affect accuracy. It was eventually added to ensure effective crimping and prevent the projectile from moving back into the case, causing a malfunction during auto-load feeding. Although the temperature-sensitive powder and new bullet changed specifications, the designation remained as the MOD 1. According to US DoD sources, the Mk 262 round is capable of making kills at 700 meters. Ballistics tests found that the round caused "consistent initial yaw in soft tissue" between 3 and 4 inches at ranges from 15 feet to 300 meters. Apparently, it is superior to the standard M855 round when fired from an M4 or M16 rifle, increasing accuracy from 3–5 minutes of angle to 2 minutes of angle. It possesses superior stopping power and can extend engagements to up to 700 meters when fired from an 18-inch barrel. It appears that this round can drastically improve the performance of any AR-15 weapon chambered to .223/5.56 mm. Superior accuracy, wounding capacity, stopping power, and range have made this the preferred round of many special forces operators and a highly desirable replacement for the older, Belgian-designed 5.56×45mm SS109/M855 NATO round. In one engagement, a two-man special forces team reported 75 kills with 77 rounds. The Mk 262 has a higher ballistic coefficient than the M855 of (G1)0.362 / (G7)0.181, meaning it loses less velocity at long-range. Mk 318 Following early engagements in Afghanistan and Iraq, U.S. Special Operations Forces reported that M855 ammunition used in M4A1 rifles was ineffective. In 2005, the Pentagon issued a formal request to the ammunition industry for "enhanced" ammunition. The only business that responded was the Federal Cartridge Company, owned by Alliant Techsystems. Working with the Naval Surface Warfare Center Crane Division, the team created performance objectives for the new ammo: increased consistency from shot to shot regardless of temperature changes, accuracy out of an M4A1 better than 2 minute of angle (2 inches at 100 yards, 6.3 inches at 300 yards), increased stopping power after passing through "intermediate barriers" like walls and car windshields, increased performance and decreased muzzle flash out of shorter barrel FN SCAR rifles, and costs close to the M855. The prototypes were delivered to the government in August 2007. Increased velocity and decreased muzzle flash were accomplished by the type of powder used. The bullet's design was called the Open Tip Match Rear Penetrator (OTMRP). The front is an open tip backed by a lead core, while the rear half is solid brass. When the bullet hits a hard barrier, the front half of the bullet crushes against the barrier, breaking it so the penetrating half of the bullet can go through and hit the target. With the lead section penetrating the target and the brass section following, it was referred to as a "barrier blind" bullet. Officially designated the MK 318 MOD 0 "Cartridge, Caliber 5.56mm Ball, Carbine, Barrier", and called SOST (Special Operations Science and Technology) ammunition, the bullet fragments consistently, even out of a 10.5 in barrel. The lead portion fragments in the first few inches of soft tissue, then the solid copper rear penetrates 18 in of tissue (as shown through ballistic gelatin) while tumbling. Out of a 14 in barrel, the Mk 318 has a muzzle velocity of . In July 2010, the Marines purchased 1.8 million M855A1 Enhanced Performance Rounds, in addition to millions of Mk318 rounds in service, as part of its effort to replace its M855 ammo. As of May 2015, Marine combat units still deployed with a mixture of both SOST and M855 rounds. As the issue of environmentally friendly ammo grew, the Marines sought to determine whether the Mk 318's lead could be replaced while still meeting specifications. They found that by replacing the lead with copper and slightly stretching the jacket around to crimp the nose even more, the bullet's ballistic coefficient increased. To avoid visual confusion with the Mk 262 round, the bullet was entirely nickel-plated for a silver color; the enhanced silver-colored copper jacketed, open tip match, 62-grain projectile was named the MK 318 MOD 1. 5.6mm 90 assault rifle used to be issued 50 rounds of ammunition in a sealed can, to be opened only upon alert and for use while en route to join their unit. This practice was stopped in 2007. The 5.6mm 90 or 5,6mm Gw Pat 90 (5.6 mm Rifle Cartridge 90), is the standard round used by the Swiss military in its rifle, the SIG SG 550. The cartridge is also known as the Cart 5,6mm 90 F ( / ) to the French- and Italian-speaking Swiss militiamen. The Swiss refer to the round as the 5.6 mm Gw Pat 90, although it is interchangeable with the 5.56×45mm NATO and .223 Remington round. The Gw Pat 90 round firing a FMJ bullet is optimized for use in 5.56 mm (.223 in) caliber barrels with a 254 mm (1:10 in) twist rate. The Gw Pat 90 was designed for the SIG SG 550 when it came into production in 1987, replacing the SIG SG 510. Previous experience with a change in standard rifle had proved that changing the firing distance for the training ranges was more expensive than designing a new ammunition; this prompted the design of a cartridge nominally capable of 300 meters. The cartridge was also designed to reduce pollution by controlling lead emissions. The bullet was originally clad with a nickel alloy jacket; however, this was found to cause excessive barrel wear, so in 1998 the nickel jackets were replaced with tombac jackets. In addition, in 1999, a copper plug was added to the base of the bullet to address environmental concerns. It is manufactured in three variations: the standard FMJ round, the tracer round, and a blank round. The FMJ cartridge has a copper-zinc alloy case and uses a double-base propellant. The bullet is a tombac jacketed FMJ projectile with a G1 ballistic coefficient of 0.331 (ICAO) / 0.337 (Army Metro). The projectile contains approximately 95% lead, 2% tin, 3% copper and was designed for terminal ballistic instability. The required accuracy for Gw Pat 90 ammunition out of factory test barrels is 63 mm (0.72 MOA) for 10 rounds (100% radius measurement method) out to 300 m. The Gw Pat 90 cartridge dimensions are in accordance with the civilian C.I.P. standards for the .223 Remington C.I.P. chambering. The Gw Pat 90 is used both in the Swiss military and in sports shooting. The very high level of individual training in the Swiss militia (every single soldier bearing a weapon has to shoot to maintain his ability once a year; see Gun laws in Switzerland) and the overall use of the Gw Pat 90 by the many Swiss citizens who shoot in competitions and for amusement has resulted in significant input on its usage. Over 1 billion cartridges had been produced . ==See also==