Yes, they are.
These cartridges were advertised as “steel core” and sold as such. The buyer confirmed that they are M-43 projectiles.
In the U.S., the Bureau of Alcohol, Tobacco, Firearms, and Explosives (BATFE) determined that 7.62x39mm cartridges with a steel cored projectile (M-43) are armor piercing handgun ammunition. As such, these cartridges may not be sold by persons or businesses who have a Federal Firearms License (FFL), except to government or law enforcement agencies. Regular citizens may buy, sell, or possess them unless their state or local laws prohibit it.
The question remains, why was the serrated cannelure added to these projectiles?