The FN 5.7×28mm (designated as the 5.7 × 28 by the C.I.P.^[7]) is a small-caliber, high-velocity, smokeless powder, rebated rim, bottlenecked centerfire cartridge designed for handgun and personal defense weapon (PDW) uses and manufactured by FN Herstal.^[8] It is similar in length to the .22 WMR (Winchester Magnum Rimfire)(5.7×27mm)^[9]and to some degree similar also to .22 Hornet or .22 K-Hornet.^[8] Unlike many new cartridges, it has no parent case; the complete package was developed from scratch by FN.

The 5.7×28mm was developed in conjunction with the FN P90 personal defense weapon and FN Five-seven pistol, in response to NATO requests for a replacement for the 9×19mm Parabellum cartridge.^[10][11] In 2002 and 2003, NATO conducted a series of tests with the intention of standardizing a PDW cartridge as a replacement for the 9×19mm Parabellum cartridge.^[11] The tests compared the relative merits of the 5.7×28mm cartridge and the 4.6×30mm cartridge, which was created by Heckler & Koch as a competitor to the 5.7×28mm.^[11] The NATO group subsequently recommended the 5.7×28mm cartridge, citing superior performance in testing, but the German delegation objected and the standardization process was indefinitely halted.^[11]

By 2006, FN's 5.7×28mm firearms—the P90 personal defense weapon and Five-seven pistol—were in service with military and police forces in over 40 nations throughout the world.^[12] In the United States, 5.7×28mm firearms are currently used by numerous law enforcement agencies, including the U.S. Secret Service.^[13][14]

In addition to being used in the FN P90 and FN Five-seven firearms, the 5.7×28mm cartridge has subsequently been used in a number of other weapons, such as the AR-57 and FN PS90 carbines.^[15][16] Excel Arms has developed four firearms chambered in 5.7×28mm, and MasterPiece Arms offers three different firearms in 5.7×28mm.^[17][18] The 5.7×28mm cartridge itself is produced in a number of varieties, two of which—the SS195LF and SS197SR—are currently offered by FN to civilian shooters.^[15]

The 5.7×28mm cartridge was designed in response to NATO requests for a replacement for the 9×19mm Parabellum cartridge.^[19][11] According to the NATO requirement, the new cartridge was to have greater range, accuracy, and terminal performance than the 9×19mm cartridge.^[20] Additionally, it was to be capable of penetrating body armor.^[20] FN Herstal responded to the NATO requirement by developing the 5.7×28mm cartridge and two associated weapons: the FN P90 personal defense weapon (PDW) and FN Five-seven pistol.^[19]

The original 5.7×28mm cartridge, called the SS90, was introduced in 1990.^[19] It used a 1.5 gram (23 grain) plastic-core projectile, which was propelled at a muzzle velocity of roughly 850 m/s (2,800 ft/s or Mach 2.5) when fired from the P90.^[19] A United States patent application for the projectile design used in the SS90 was filed by FN's Jean-Paul Denis and Marc Neuforge in 1989.^[5] U.S. Patent 5,012,743 ("High-Performance Projectile") was received in 1991.^[6][21]

When fired from the FN P90, the 5.7×28mm SS190 can penetrate the NATO CRISAT vest or a Level IIIA Kevlar vest at a range of 200 m (219 yd).^[22][23]

The 5.7×28mm SS90 cartridge was discontinued, and replaced, in 1993, with the 5.7×28mm SS190.^[6] The SS190 uses a 2.7-mm (0.11 in) shorter projectile with a weight of 2.0 g (31 grains), which has, when fired from the P90, a muzzle velocity of roughly 715 m/s (2,350 ft/s).^[22] The shorter length of the SS190 projectile allows it to be more conveniently used in the 5.7×28mm FN Five-seven pistol, which was also being developed at that time.^[6]

In 1993, FN introduced a modified version of the P90 with a magazine adapted to use the SS190 cartridge.^[6] Several specialized 5.7×28mm varieties were also developed alongside the SS190, such as the L191 tracer round and the subsonic SB193 bullet for sound-suppressed use.^[15] The 5.7×28mm chambered FN Five-seven pistol then went into production in 1998.^[24]

In 2002 and 2003, NATO conducted a series of tests with the intention of standardizing a PDW cartridge as a replacement for the 9×19mm Parabellum.^[11] The tests compared the relative merits of the 5.7×28mm cartridge and the HK 4.6×30mm cartridge, which was created by German small arms manufacturer Heckler & Koch as a competitor to the 5.7×28mm.^[11] The results of the NATO tests were analyzed by a group formed of experts from Canada, France, the United Kingdom, and the United States, and the group's conclusion was that the 5.7×28mm was "undoubtedly" the more efficient cartridge.^[11]

Among other points, the NATO group cited superior effectiveness (27 percent greater) for the 5.7×28mm against unprotected targets and equal effectiveness against protected targets.^[11] It also cited less sensitivity to extreme temperatures for the 5.7×28mm, and cited a greater potential risk of barrel erosion with the 4.6×30mm.^[11] In addition, the group pointed out that 5.7×28mm is close to the 5.56×45mm NATO by its design and manufacture process, allowing it to be manufactured on existing production lines.^[11] The group also noted that 5.7×28mm firearms had existed for a longer period of time than 4.6×30mm firearms, and that the 5.7×28mm FN Five-seven pistol was already in production at that time, while the 4.6×30mm Heckler & Koch UCP pistol was a new concept.^[11]

However, the German delegation and others rejected the NATO recommendation that 5.7×28mm be standardized, halting the standardization process indefinitely.^[11][20] As a result, both the 4.6×30mm and 5.7×28mm cartridges (and the associated weapons) have been independently adopted by various NATO countries, according to preference; both the P90 and Five-seven are currently in service with military and police forces in over 40 nations throughout the world.^[11]

In 2004, the SS192 hollow-point cartridge was introduced to civilian shooters alongside the new IOM variant of the Five-seven pistol.^[25] After being met with controversy, the SS192 variety was discontinued in the same year, and in 2005 the SS196SR variety was introduced using a 2.6 g (40 grain) Hornady V-Max projectile.^[26][27] The SS196 was also quickly discontinued in favor of the newer SS195LF and SS197SR varieties, which are currently offered to civilian shooters for use in 5.7×28mm firearms, followed by the SS198LF variety, which is currently produced but is restricted by FN to military and law enforcement customers.^[15]

FN's 5.7×28mm ammunition types were briefly manufactured by Olin-Winchester, but today they are made by FN Herstal in Belgium and (since 2006) Fiocchi in the United States.^[8][28] In 2009, the National Rifle Association added 5.7×28mm firearms to its NRA Tactical Police Competition standards, allowing law enforcement agencies to compete in this event using 5.7×28mm firearms.^[29] Starting in 2012, Federal began producing a new 5.7×28mm round for civilian shooters, designated the AE5728A.^[18]

The 5.7×28mm cartridge was designed by FN Herstal specifically for use in the FN P90 personal defense weapon and FN Five-seven pistol.^[10] Subsequently, it has been used in a number of other weapons, such as the FN PS90 carbine and the AR-57, an upper receiver for M16 and AR-15 rifles.^[15][16] The ST Kinetics CPW can be configured for the 5.7×28mm cartridge by changing the barrel and magazine groups.^[30] Excel Arms has developed four firearms chambered in 5.7×28mm,^[17] and MasterPiece Arms offers three different 5.7×28mm firearms.^[18]

The 5.7×28mm cartridge weighs 6.0 grams (93 grains)—roughly half as much as a typical 9×19mm Parabellum cartridge—making extra ammunition less burdensome, or allowing more ammunition to be carried for the same weight.^[31][32][33] Since the 5.7×28mm cartridge also has a relatively small diameter, a relatively high number of cartridges can be contained in a magazine.^[34] The cartridge has a loud report and produces considerable muzzle flash (when fired from a pistol),^[35] but it has roughly 30 percent less recoil than the 9×19mm cartridge, improving controllability.^[33][23][36] Due to its high velocity, the 5.7×28mm also exhibits an exceptionally flat trajectory.^[33][37]

One of the design intents of the SS190 variety of this cartridge was that it have the ability to penetrate Kevlar protective vests—such as the NATO CRISAT vest—that will stop conventional pistol bullets.^[23] Fired from the P90, the SS190 is capable of penetrating the CRISAT vest at a range of 200 m (219 yd), or a Level IIIA Kevlar vest at the same range.^[22][23] However, sporting variants of the 5.7×28mm are classified by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) as not armor-piercing.^[26]

According to FN, the 5.7×28mm cartridge has an effective range of 200 m (219 yd) and a maximum range of 1,800 m (1,969 yd) when fired from the P90,^[28] and an effective range of 50 m (55 yd) and a maximum range of 1,510 m (1,651 yd) when fired from the Five-seven.^[25] In testing, the SS190 and similar 5.7×28mm projectiles consistently turn base over point ("tumble") as they pass through ballistic gelatin and other media, using the 21.6-mm (.85 in) projectile length^[25] to create a larger wound cavity.^{[10][32][38][39]} However, some are skeptical of the bullet's terminal performance, and it is a subject of debate among civilian shooters in the United States.^[39]

The 5.7×28mm projectile potentially poses less risk of collateral damage than conventional pistol bullets, because the projectile design limits overpenetration, as well as risk of ricochet.^[38][40][41] The lightweight projectile also poses less risk of collateral damage in the event of a miss, because it loses much of its kinetic energy after traveling only 400 m (437 yd), whereas a conventional pistol bullet such as the 9×19mm retains significant energy beyond 800 m (875 yd).^[37] This range exceeds the engagement distances expected for the 5.7×28mm cartridge's intended applications, so the cartridge's limited energy at long range is not conversely considered to be disadvantageous.^[37]

Since the 5.7×28mm SS190 projectile does not rely on fragmentation or the expansion of a hollow-point bullet, the cartridge (and 5.7×28mm firearms) are considered suitable for military use under the Hague Convention of 1899, which prohibits the use of expanding bullets in warfare.^[39]

FN's 5.7×28mm cartridge cases are covered with a special polymer coating for easier extraction with the PS90 carbine due to the high chamber pressures and lack of case tapering.^[32] In addition, this coating ensures proper feeding and function in the magazines.^[32]

The 5.7×28mm has a cartridge case capacity of 0.90 ml (13.85 grains H2O).^[35]

Americans define the shoulder angle at alpha/2 ≈ 35 degrees. The common rifling twist rate for this cartridge is 1:228.6 mm (1:9 in), 8 grooves, Ø lands = 5.53 mm, Ø grooves = 5.62 mm, land width = 1.63 mm and the recommended primer type is small rifle.^[7]

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings, the 5.7×28mm can handle up to 3,450 bar (345 MPa; 50,000 psi) Pmax (the nominal maximum) piezo pressure. In C.I.P. regulated countries, every rifle cartridge combination has to be proofed at 125% of this maximum C.I.P. pressure to be certified for sale to consumers, referred to as "PE". This means that 5.7×28mm chambered arms in C.I.P. regulated countries are currently (2018) proof tested at 4,313 bar (431.3 MPa; 62,550 psi) PE piezo pressure.^[7]

Fired from the longer 40.74 cm (16.04 in) barrel of the PS90, the muzzle velocity of SS195LF is roughly 60 m/s (200 ft/s) faster, and the muzzle velocity of SS197SR is roughly 45 m/s (150 ft/s) faster.^[42] Fired from the shorter 12.2 cm (4.8 in) barrel of the Five-seven pistol, the muzzle velocity of SS195LF is roughly 90 m/s (300 ft/s) slower, and the muzzle velocity of SS197SR is roughly 60 m/s (200 ft/s) slower.^{[42] [51][52]}