The 5.56 mm Cartridge was officially adopted by the U.S. Army in 1964 under the nomenclature: "5.56mm Ball cartridge M193". It was developed from the .223 Remington in a design competition to replace the 7.62mm cartridge as the U.S. military standard. Also called the .223 or 5.56 x 45mm, this cartridge is now the primary U.S. and NATO military rifle round. NATO forces, including the U.S., have upgraded the M193 to a new heavier bullet 5.56 x 45mm round, the SS109 from FN of Belgium.
5.56mm ammo packaged in two M2A1 cans with wirebound crate, 1680 rounds total.
The 5.56mm cartridge was designed by Robert Hutton, then technical editor of Guns & Ammo magazine and owner of a California range. He responded to Army requirements for a round for the AR-15 whose projectile would exceed Mach 1 at 500 meters, a high standard for that time. Hutton teamed with Gene Stoner of Armalite to produce the winning design, a .222 with a longer case and 55 grain Sierra boat tail bullet. [See Guns & Ammo Annual for 1971].
The M193 round has been an effective military cartridge that met its design expectations. It is shorter range but just as lethal as the Cal. .30 and 7.62 rifle rounds it replaced while its much lighter weight gave soldiers the opportunity to carry many more rounds into the battle. Recently the 5.56 x 45mm M193 has been improved by adoption of the NATO approved SS109, developed by FN (Fabrique Nationale) of Belgium, that differs primarily in that the bullet is heavier.
When packaged for the rifles, three ten round clips will be inserted into a point protector paperboad carton and then four cartons will be packed in a 4 pocket bandoleer, for a total of 120 rounds per bandoleer. Seven such bandoleers will be packed into an M2A1 ammo can (NSN 8140-00-960-1699, holds 840 rounds) and two M2A1s will be packed together in a wirebound wooden crate (1680 rounds) as in the top photo on this page. The crates are shipped 48 to a pallet.
Prior to the four pocket bandoleers, there were 6 and 7 pocket bandoleers, typical in Vietnam. With those, there were two stripper clips in a cardboard sleeve in each pocket, for a total of 6x20=120 or 7x20=140 rounds per bandoleer. There were then 840/120=7 or 840/140=6 bandoleers per ammo can, always a total of 840 rounds per can. With each bandoleer, there was a metal magazine guide for speed loading the stripper clips into either 20 or 30 round magazines. The photo to the right shows the markings on a six pocket bandoleer.
For training purposes the military has been experimenting with fiberboard boxes for the 5.56mm ammo to save on the cost of delivering ammo cans, bandoleers and other disposable packaging. Mission packaging is not changed, bandoleers and ammo cans will still be used.
Linked 5.56mm ammo came in 200 round magazines for the M249 SAW packed into 800 cartridge PA-108 'Fat 50' Ammunition Cans. Belts typically had 4 M855 ball and 1 M856 tracer in repeating pattern connected with M27 steel links.
Types of 5.56 mm Ammunition in the U.S. Military
Cartridge, 5.56mm, Ball, M193
Cartridge, 5.56mm, Grenade, M195
Cartridge, 5.56mm, Tracer, M196
Cartridge, 5.56mm, High Pressure Test, M197
Cartridge, Dummy, 5.56mm, M199
Cartridge, 5.56mm, Blank, M200
Cartridge, Dummy, 5.56mm, M232
Cartridge, 5.56mm, Blank, M755
Cartridge, 5.56mm, Ball, M855
Cartridge, 5.56mm, Ball, M855A1
Cartridge, 5.56mm, Tracer, M856
Cartridge, 5.56mm, Plastic, Practice, M862
Cartridge, 5.56mm, Armor Piercing (AP), M995
Technical Specifications for the NATO SS109 5.56 Round
Muzzle Velocity at 78 feet (24 meters)
Muzzle Energy at 78 feet (24 meters)
Maximum Average +3SD
Accuracy SDX;SDY;MAX 3 X 30 rounds
8.8" at 660 yards or 7.9" at 600 yards
22.5 cm at 600 m or 20.0 cm at 550 m
Complete penetration of SAE 1010/1020
steel plate, 3.5 mm thickness
placed at a distance of 625 yards
(570 meters) from the muzzle.
Cartridge, 5.56mm, Ball, M855A1 Enhanced Performance Round and MK318 MOD 0
The M855 was developed in the 1970s and adopted by NATO, including the U.S., in 1980. The M855 was not effective in many situations, lacking the stopping power to reliably disable enemy combatants or to penetrate light barriers and obstacles like car windshields. Under the U.S. Army "green bullet program", started in 1996, a cartridge was developed that would be both lead-free (the "green" part) and also pack more punch. Several experimental rounds were tested under the nomenclature Cartridge, 5.56mm, Ball, M855A1 for potential adoption by the Army and Marine Corps. However, in field trials the new ammo designs had problems that prevented adoption. The very promising M855A1 LFS (Lead Free Slug, made of an alloy of bismuth-tin with a steel penetrator) went into testing in 2007, but in August 2009 the M855A1 LFS was deemed a failure and was dropped from consideration.
The continuing delays were too much for the Marine Corps, who cancelled plans to adopt the Army M855A1 in 2010 and instead procured the Special Operations Command (SOCOM) enhanced 62 grain 5.56mm Special Operations Science and Technology (SOST) round for Marine use in Afghanistan. Formally known as the MK318 MOD 0, the SOST ammo stays on target longer and is more accurate when fired from short-barrel weapons. Having a lead core with a solid copper shank, SOST ammo is not lead-free like the Army wanted, but it does the job for the Marines.
On 23 June 2010, the Army announced it had completed testing and had begun shipping the M855A1 5.56mm Enhanced Performance Round to support warfighters in Afghanistan. In this design, the M855A1 enhancements include improved hard-target capability, more dependable, consistent performance at all distances, improved accuracy, reduced muzzle flash and a higher velocity. In testing, the M855A1 exceeded the performance of the M855 and even the performance of 7.62mm ball ammunition against certain types of targets, blurring performance differences between 5.56 and 7.62mm rounds. The M855A1 has the same weight, trajectory, and handling characteristics of the M855 so there is no additional training required.
The M855A1 is tailored for use in the M4 Carbine Weapon System but also vastly improves the performance of the M16 and M249 families of weapons. It is hailed as a true general purpose round since it outperforms earlier rounds across the spectrum of target types.
The Army planned to procure 200 millions M855A1 rounds, the most tested small arms round ever, over the 12-15 months following June 2010. The M855A1 Enhanced Performance Round is a "green" success, with an environmentally-friendly lead-free projectile that eliminates the use of up to 2,000 tons of lead each year. Unlike earlier rounds, the M855A1 can be used on training ranges where lead restrictions are enforced.
As of December 2009, the formal designation for the M855A1 cartridges included:
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