5.7mm

The FN 5.7×28mm (designated as the 5.7×28 by the C.I.P. and FN 5.7×28mm NATO) is a small-caliber, high-velocity, smokeless-powder, rebated, non-tapered, bottleneck, centerfire cartridge designed for pistols and personal defense weapons (PDW) uses, manufactured by FN Herstal. It is similar in length to the .22 WMR and .22 Hornet. 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 PDW and later the FN Five-seven pistol in response to NATO requests as a replacement for the 9×19mm Parabellum cartridge. In 2002 and 2003, NATO conducted a series of tests to find a replacement. 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. 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 halted until 2021 when it was officially adopted as a NATO standard Standardization Agreement (STANAG) 4509.
By 2006, FN's 5.7×28mm firearms—the P90 PDW and Five-seven pistol—were in service with military and police forces in over 40 nations throughout the world. In the United States, 5.7×28mm firearms are currently used by numerous law enforcement agencies, including the U.S. Secret Service.
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. Excel Arms has developed four firearms chambered in 5.7×28mm, MasterPiece Arms offers three different firearms in 5.7×28mm., and CMMG offers several of its AR-Style Banshee firearms in 5.7x28. As of December, 2019, Ruger offers its Ruger-57 semi-automatic pistol chambered in this cartridge. January 2021 saw the announcement by Kel-Tec of the P50 handgun, which uses 50 round P90 magazines. Palmetto State Armory introduced its Rock 5.7 pistol in January 2022; it became available for purchase in May 2022. In January 2023, Smith & Wesson introduced the M&P 5.7 gas assisted pistol. In January 2024, TİSAŞ introduced the PX-5.7, the first Turkish-made 5.7x28 pistol made.
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.

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