When FNH USA introduced the Five-seveN pistol in 2004 it became quite a controversial weapon. It was initially introduced as a compliment to the P90 that had been making the rounds of many police departments and was a law enforcement restricted product. Many agencies and operators were moving to match their primary and secondary weapon calibers. The big move to the 5.56mm rifle had not really occurred yet and most were using a sub-machinegun of some type. It made sense to use one type of ammunition for many, if for no other reason than the logistics of ammunition supply. For those teams that had made the move initially to the P90 the Five-seveN pistol made perfect sense. The 5.7x28mm cartridge was not chambered in anything else at the time so these two complimented each other well. Many of the characteristics that brought the P90 to SWAT teams at the time were shared by the Five-seveN pistol. Lightweight, low recoil, accuracy, and high capacity were just a few.
The 5.7x28mm round was initially designed to meet the Personal Defense Weapons (PDW) requirements. This and other rounds were designed to penetrate body armor of the era and still be lethal well past 100 meters. The shorter barrel of the pistol provided for some limitations, but it was still pretty penetrative. It is a small bullet (25 to 40 grains) traveling at high velocities. Velocities well over 2000 fps (feet per second) were the norm in the P90, and slightly less in the Five-seveN pistol.
The initial ammunition (SS190), which met this criteria was restricted to law enforcement and military so it was mostly a discussion amongst operators and the many “experts” out there. The initial design was primarily a solution to a military problem. Militaries are prohibited from using expanding ammunition for the most part. In order to meet The Hague conventions, this round was designed to penetrate then immediately tumble. In theory at least this would create a permanent wound channel similar to those made by hollow points and meet these requirements.