No, its illegal to manufacture NEW AP ammo for the civillian market. The law is much like the magazine limit law- you can buy, sell, and use hi cap magazines, but its a felony to make a hi-cap magazine unless its for the military or stamped for "law enforcement only" which is illegal for a non LEO to possess.
There is alot of .50 bmg AP and incediary on the market- perfectly legal.
30-06 AP ammo isn't too hard to find, I know of a source of pulled 30-06 AP bullets, all perfectly legal.
Boatloads of 7.62x39 AP and 8x57 steel core surplus stuff out there.
If you were to take the pulled 30-06 bullets and load them into anything other than 30-06, you might be treading into a very dark gray area of the law, but then again noone is going to know unless you tell someone about it.

Making your own AP bullets becomes a felony the moment you load them into a cartridge.