M2 Ball (WW2) is lead point filler inside the bullet, no base plug, the jacket just wraps around the base.
M33 Ball (current) has an inert point filler, monosodium carbonate powder or some such, inside the bullet tip with a lead base plug.
M8 API (silver tip) has incendiary powder in the inside of the point of the bullet and a lead base plug.
As to cores, All ball is soft steel, APx (AP, API, etc) is hard core. The ball has a groove around the core which is the result of the bullet cannelure being "rolled" into bullet after it's assembled, the knurled cannelure. AP is too hard a core to roll a cannelure into the bullet, so it's cut (smooth cannelure). That means no groove around the core.
The knurled cannelure, the lead base plug and the weight of the original poster's bullet means M33 Ball. (Confirmed by the point filler and groove in the bullet core)