Reply #14: I have one ATF link

[Euromutt]

http://www.atf.gov/firearms/firearmstech/fabriquen.htm

FTB has also examined a 5.7 X 28 mm projectile that FN Herstal has designated the "SS196." The SS196 is loaded with a Hornady 40 grain, jacketed lead bullet. FTB classified SS196 ammunition as not armor piercing ammunition under Federal firearms statutes.

According to FNH USA, FN Herstal tested the SS192 ammunition. SS192 ammunition did not penetrate the Level IIIA vests that were tested. FNH USA states that SS196, Hornady V-Max 40 gr. bullets fired from a 4-3/4 inch barrel did not penetrate the Level II vests that were used in testing.

It doesn't entirely cover the topic at hand, because the SS196 was discontinued in favor of the SS197SR, which is essentially the same round, only loaded for a muzzle velocity about 100fps higher than the SS196. Still unlikely to penetrate a level II vest, though.