The statute reads "beryllium copper". There is a typo or deliberate use of a comma between "beryllium" and "copper" in the BATFE announcement.
Had to look up pogue. In any event, reading the statute suggests that solid copper handgun ammunition could be classified as "armor piercing,"
The use of 100 percent pure copper in a handgun caliber bullet is legal. Several bullet makers use pure copper in their handgun caliber bullets: Barnes, for one. i often use the excellent Barnes 225 grain .430 handgun bullet in my muzzleloader when hunting hogs.
A few months Elite Ammunition got into trouble for making handgun caliber bullets from an alloy of copper and zinc=brass. Elite Ammo touted the capabilities of their 5.7 ammo:
This video was made by Elite Ammuntion: