The FN-designed 5.7x28mm caliber has joined the ranks of 5.56 and 7.62 by recently being standardized by NATO.

Designed in the late 1980s for use in Personal Defense Weapons, or PDWs, the 5.7 was first marketed by FN in the early 1990s in its P90/S PDW/carbine and Five-seveN pistol. Since then, those guns have been adopted with military and police forces in more than 40 countries and sold widely on the commercial market.

Now, some three decades after it was introduced, the Western defense alliance recognized the caliber under standardization agreement (STANAG) 4509, which integrates it into the latest AEP-97 – NATO's Multi-Caliber Manual Of Proof and Inspection. 

"As a NATO standardized caliber, the 5.7x28mm provides armies with the guarantee of interchangeability between ammunition from different manufacturers and operational efficiency in weapons of this caliber," explains FN in a statement. 
 

For reference, 7.62 NATO was standardized in 1957 and 5.56 NATO in 1981. 

The news comes as platform-limited 5.7, which had largely petered out by the 2010s, is seeing a resurgence as new manufacturers ranging from boutique gunmakers like Diamondback, CMMG, and KelTec to household names such as Ruger, are introducing exciting new firearm models chambered for the caliber. Further, ammo makers are promising fresh loads to the market such as Speer's new Gold Dot, to help gun owners looking for viable 5.7 rounds to fill their needs. 
 

Since you came this far, check out our factory tour of FN's Columbia, South Carolina, facility below, where we see where the "World's Most Battle-Proven Firearms" are crafted.