Armor piercing ammo has always been a grey area that most do not understand. Frankly, unless you're carrying or have memorized a military spec book, you really don't know what ammo is what. Even worse, a lot of ammo is sold outside of its original packaging and all info is lost except the military headstamp and a black tip. There was the original AP ammo made early and before WWII that was a steel insert/core inside of a lead surround with a copper jacket. During the early part of the war, the inserts/core became a tungsten carbide core weighing in at 168.5 grs. Both bullets were made and issued during the war. The difference was on the packaging. It would have been marked as 30 caliber M2 ammo or it would have had a number like 1774, 1830, 559 as the ammo type. All of it is black tipped. The 30 caliber M2 is of the steel core type, the others carry a tungsten carbide core. Unless you have the original packaging, you're not going to know. Rarely will you come across AP ammo that has a heavy bullet-241grs. These carry the tungsten carbide core/insert and were used primarily by the Navy. I've only seen one box in my 66 years but not all AP is 150gr as there are many bullet weights.