User blog comment:Callofduty4/Modern Warfare 3 Spec Ops shown at Late Night with Jimmy Fallon/@comment-3121225-20110614230945/@comment-98.68.156.40-20110615012751

The Five-Seven fires 5.7x28mm, which was designed to replace 9mm. Ballistically, the 5.7x28 is very similar to the .22 WMR or .22 Hornet; however, it penetrates Kevlar Vests with ease. It is a PDW cartridge, not a rifle cartridge.