5.56×45mm NATO - Misplaced Pages

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5.56x45mm NATO

5.56x45mm NATO (left) next to .30-30 Winchester (center) and 7.62x51mm NATO (right)

Type

Rifle

Place of origin

United States of America

Service history

Used by

NATO

Wars

Vietnam War–present

Production history

Designer

Remington Arms

Specifications

Parent case

.223 Remington

Case type

Rimless, bottleneck

Bullet diameter

5.70 mm (0.224 in)

Neck diameter

6.43 mm (0.253 in)

Shoulder diameter

9.00 mm (0.354 in)

Base diameter

9.58 mm (0.377 in)

Rim diameter

9.60 mm (0.378 in)

Rim thickness

1.14 mm (0.045 in)

Case length

44.70 mm (1.760 in)

Overall length

57.40 mm (2.260 in)

Rifling twist

178 mm or 229 mm (1 in 7" or 9")

Primer type

Small rifle

Maximum pressure

430.00 MPa (62,366 psi)

Ballistic performance

Bullet mass/type	Velocity	Energy
4 g (62 gr) SS109 FMJBT	940 m/s (3,100 ft/s)	1,767 J (1,303 ft⋅lbf)
4.1 g (63 gr) DM11 FMJBT	936 m/s (3,070 ft/s)	1,796 J (1,325 ft⋅lbf)
4.1 g (63 gr) GP 90 FMJBT	905 m/s (2,970 ft/s)	1,679 J (1,238 ft⋅lbf)

Source(s): NATO EPVAT testing, QuickLOAD, SAAMI, C.I.P.

5.56x45mm NATO is a rifle cartridge developed in the United States and originally chambered in the M16 rifle. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries. It is derived from, but not identical to, the .223 Remington cartridge.

History

The previous standard NATO rifle cartridge was the 7.62x51mm NATO, derived from the .308 Winchester rifle cartridge and designed to replace the U.S. military's .30-06 Springfield rifle cartridge. At the time of selection, there had been criticism that the 7.62 mm was too powerful for modern service rifles, causing excessive recoil, and that the weight of the ammunition did not allow for enough fire power in modern combat. A soldier can carry nearly twice as much 5.56 mm ammunition as 7.62 mm for the same weight.

During the late 1950s, ArmaLite and other U.S. firearm designers started their individual Small Caliber/High Velocity (SCHV) assault rifle experiments using the commercial .222 Remington cartridge. When it became clear that there was not enough powder capacity to meet U.S. Continental Army Command's (CONARC) velocity and penetration requirements, ArmaLite contacted Remington to create a similar cartridge with a longer case body and shorter neck. This became the .222 Remington Special. At the same time, Springfield Armory's Earle Harvey had Remington create an even longer cartridge case then known as the .224 Springfield. Springfield was forced to drop out of the CONARC competition, and thus the .224 Springfield was later released as a commercial sporting cartridge known as the .222 Remington Magnum. To prevent confusion with all of the competing .222 cartridge designations, the .222 Remington Special was renamed the .223 Remington. After playing with their own proprietary cartridge case design, the .224E1 Winchester, Winchester eventually standardized their case dimensions, but not overall loaded length, with the .222 Remington Special to create a cartridge known as the .224E2 Winchester. With the U.S. military adoption of the ArmaLite AR-15 as the M16 rifle in 1963, the .223 Remington was standardized as the 5.56x45mm. However, the .223 Remington was not introduced as a commercial sporting cartridge until 1964.

The British had extensive evidence with their own experiments into an intermediate cartridge since 1945 and were on the point of introducing a .280 inch (7 mm) cartridge when the selection of the 7.62 mm NATO was made. The FN company had also been involved. The concerns about recoil and effectiveness were effectively overruled by the US within NATO, and the other NATO nations accepted that standardization was more important at the time than selection of the ideal cartridge. However the concerns would prove to be valid and led to the development of the 5.56 cartridge.

During the 1970s, NATO members signed an agreement to select a second, smaller caliber cartridge to replace the 7.62 mm NATO. Of the cartridges tendered, the 5.56 mm was successful, but not the 5.56 mm loading (3.56 g (55 gr), M193 Ball) as used by the U.S. at that time. Instead, the Belgian FN SS109 loading was chosen for standardization. The SS109 used a heavier 4 g (62 gr) bullet with a steel core inserted, fired at a lower muzzle velocity for better long-range performance, specifically to meet a requirement that the bullet be able to penetrate through one side of a steel helmet at 600 m. Some believe that this requirement has made the M855 less capable of fragmentation than the M193 as discussed below.

Cartridge dimensions

The 5.56x45mm NATO has 1.85 ml (28.5 grains H₂O) cartridge case capacity.

5.56x45mm NATO maximum NATO cartridge dimensions. All sizes in millimeters (mm).

Americans would define the shoulder angle at alpha/2 = 23 degrees. The common rifling twist rate for this cartridge is 178 mm (1 in 7 in) or 229 mm (1 in 9 in), 6 grooves, Ø lands = 5.56 mm, Ø grooves = 5.59 mm, land width = 1.88 mm and the primer type is small rifle.

According to the official NATO proofing guidelines the 5.56x45mm NATO case can handle up to 430 MPa (62,367 psi) piezo service pressure. In NATO regulated organizations every rifle cartridge combo has to be proofed at 125% of this maximum pressure to certify for service issue. This is equal to the C.I.P. maximum pressure guideline for the .223 Remington cartridge, that is the 5.56x45mm NATO parent cartridge.

Performance

The 5.56x45mm NATO cartridge with the standard military ball bullet (NATO: SS109; U.S.: M855) will penetrate approximately 15 to 20 inches (38 to 50 cm) 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 2,700 ft/s (820 m/s), it may yaw and then fragment at the cannelure (the 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, impart much greater damage to tissue than bullet dimensions and velocities would suggest. This fragmentation effect is highly dependent on velocity, and therefore barrel length: short-barreled rifles generate less muzzle velocity and therefore lose effectiveness at much shorter ranges than longer-barreled rifles.

There has been much criticism of the poor performance of the bullet on target, especially the first-shot kill rate when using firearms that don't achieve the velocity to cause fragmentation. This typically becomes an issue at longer ranges (over 100 m) or when penetrating heavy clothing, but this problem is compounded in shorter-barreled weapons. The 14.5-inch (37 cm) barrel of the U.S. military's M4 carbine can be particularly prone to this problem. At short ranges, the bullet is reported to be mostly effective, and its tendency to fragment reduces the risk of overpenetration when used at close range. However, if the bullet is moving too slowly to reliably fragment on impact, the wound size and potential to incapacitate a person is greatly reduced. Several alternate cartridges have been developed in an attempt to address the perceived shortcomings of 5.56 mm ammunition including the 6.5 mm Grendel and the 6.8 mm Remington SPC.

Recently, advances have been made in 5.56 mm ammunition. The US military has adopted for limited issue a 77-grain (5.0 g) "Match" bullet, type classified as the Mk 262. The heavy, lightly constructed bullet fragments more violently at short range and also has a longer fragmentation range. 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.

5.56mm NATO versus .223 Remington

The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military cases are generally made from thicker brass than commercial cases; this reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56 mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 137.9 MPa (20,000 psi) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,366 psi) for 5.56 mm NATO, is reduced by SAAMI to 379.21 MPa (55,000 psi) for .223 Remington. In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56 mm NATO.

The 5.56 mm NATO chambering, known as a NATO or mil-spec chamber, has a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 Remington chambering, known as 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 mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56 mm NATO chamber specification.

Using commercial .223 Remington cartridges in a 5.56 mm NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered gun due to the longer leade. Using 5.56 mm NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice. Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14, 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 mm NATO ammunition.

Comparison of 5.56mm versus 7.62mm NATO

Cartridge	Cartridge size	Bullet weight	Velocity	Energy
5.56 mm NATO	5.56x45mm	3.95–5.18 g	772–930 m/s (2526–3051 ft/s)	1,177–1,708 J
7.62mm NATO	7.62x51mm	9.33 g	838 m/s (2749 ft/s)	3,275 J

NATO Ball (U.S.: M855) can penetrate up to 3 mm (about 1/8") of steel at 600 meters. According to Nammo, a Norwegian ammunition producer, the M995 can penetrate up to 12 mm (nearly 1/2") of RHA steel at 100 meters.

Military cartridge types

Cartridge, Ball, F1 (Australia): 5.56x45mm FN SS109 equivalent produced by Australian Defence Industries(ADI), now Thales Australia.
Cartridge, Blank, F3 (Australia): 5.56x45mm Blank cartridge produced by Australian Defence Industries(ADI), now Thales Australia.
Cartridge, Ball, C77 (Canada): 5.56x45mm FN SS109 equivalent used in both C7, C8 and C9 type weapons.
Cartridge, Blank, C79 (Canada): 5.56x45mm blank cartridge used in both C7, C8 and C9 type weapons.
Cartridge, Ball, DM11 (Germany): 5.56x45mm 4.1 g dual core ball cartridge, green tip w/steel core, produced by RUAG Ammotech.
Cartridge, Tracer, DM21 (Germany): 5.56x45mm tracer compliment to DM11, also produced by RUAG Ammotech.
Cartridge, Ball, L2A1 (United Kingdom): 5.56x45mm FN SS109 equivalent produced by Radway Green.
Cartridge, Tracer, L1A1 (United Kingdom): 5.56x45mm tracer compliment to L2A1, also produced by Radway Green.

Cartridge, Caliber 5.56 mm, Ball, M193 (United States): 5.56x45mm 55-grain ball cartridge.
Cartridge, Caliber 5.56 mm, Grenade, M195 (United States): 5.56x45mm grenade launching blank.
Cartridge, Caliber 5.56 mm, Tracer, M196 (United States): 5.56x45mm 54-grain tracer cartridge, red cartridge tip.
Cartridge, Caliber 5.56 mm, Ball, M202 (United States): 5.56x45mm 58-grain FN SSX822 cartridge
Cartridge, Caliber 5.56 mm, Ball, XM287 (United States): 5.56x45mm 68-grain ball cartridge produced by Industries Valcartier, Inc. An Improved version was also produced designated XM779.
Cartridge, Caliber 5.56 mm, Tracer, XM288 (United States): 5.56x45mm 68-grain tracer cartridge produced by Industries Valcartier, Inc. An Improved version was also produced designated XM780.
Cartridge, Caliber 5.56 mm, Grenade, M755 (United States): 5.56x45mm grenade launching blank specifically for the M234 launcher.
Cartridge, Caliber 5.56 mm, Ball, XM777 (United States): 5.56x45mm ball cartridge.
Cartridge, Caliber 5.56 mm, Tracer, XM778 (United States): 5.56x45mm tracer cartridge.
Cartridge, Caliber 5.56 mm, Ball, M855 (United States): 5.56x45mm 62-grain FN SS109 ball cartridge, green tip w/steel penetrator and a lead core.
Cartridge, Caliber 5.56 mm, Ball, M855 Lead Free (United States):62-grain green tip w/tungsten penetrator and a steel core. Primarily used during training in countries with strict lead disposal laws.
Cartridge, Caliber 5.56 mm, Tracer, M856 (United States): 5.56x45mm 64-grain FN L110 tracer cartridge
Cartridge, Caliber 5.56 mm, Armor Piercing, M995 (United States): 5.56x45mm 52-grain AP cartridge, black cartridge tip.
Cartridge, Caliber 5.56 mm, Tracer, XM996 (United States): 5.56x45mm so-called "Dim Tracer" with reduced effect primarily for use with night vision devices.
Cartridge, Caliber 5.56mm, Special Ball, Long Range, Mk 262 Mod 0/1 (United States): 5.56x45mm 77-grain Open-Tipped Match/Hollow-Point Boat-Tail cartridge. Mod 0 features Sierra Matchking bullet, while Mod 1 features either Nosler or Sierra bullet.
Cartridge, 5.64 mm, Ball, MLU-26/P (United States): Early USAF designation for 5.56x45mm ball cartridge produced by Remington.

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 77-grain (5.0 g) bullet that is more effective at longer ranges than the standard issue M855 round.

Two versions of the round have been procured to date. Initial production runs, designated Mark 262 Mod 0, lacked a cannelure. Subsequent production, designated Mk 262 Mod 1, added a cannelure to the bullet for effective crimping.

5.6mm Gw Pat 90

Swiss Army 50-round Gw Pat 90 ammunition box.

The 5,6mm Gw Pat 90 or GP 90 (5.6mm 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 F to the French and Italian speaking Swiss militiamen. The Swiss refer to the round as the 5,6mm Gw Pat 90, although it is interchangeable with the 5.56x45mm NATO and .223 Remington round. The Gw Pat 90 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 of a change in standard rifle had proved that changing the distance of fire for the training ranges was more expensive than the design of a new ammunition; this prompted the design of a cartridge nominally capable at 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.

The ammunition is currently (2009) produced by RUAG Ammotec, a subsidiary of the RUAG group. The ammunition is manufactured in three variations: the standard FMJ round, the tracer round, and a blank round. The FMJ cartridge has a CuZn-alloy case and uses a double base propellant. The bullet is a 4.1 g (63 gr) tombac jacketed FMJ projectile with a ballistic coefficient of 0.331 (ICAO) / 0.337 (Army Metro). The projectile contains approximately 95% Pb, 2% Sb, 3% Cu, 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 sport shooting. The very high level of individual training in the Swiss militia (every single soldier bearing a weapon has to shoot for qualification once a year; see Gun politics 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 have been produced as of 2005.