18 U.S.C. § 921(a)(17)(B)
(B) The term “armor piercing ammunition” means—
(i) a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium; or
(ii) a full jacketed projectile larger than .22 caliber designed and intended for use in a handgun and whose jacket has a weight of more than 25 percent of the total weight of the projectile.
or for less accuracy and more hype:
http://youtu.be/-c1mzkAtHPI
The 90s were almost as strange as the 80s but with more subdued fashion choices.