Interesting. When I was shooting a .45-70 there was some good research and evidence demonstrating that when loaded with similar wide meplat hard cast bullets at mild velocities it would give excellent penetration, exceeding that of the faster .458 magnums. Penetration was almost inversely proportionate to impact velocity. Of course, the magnum rounds expended more energy on impact, and had better in flight ballistics, but there was something to be said for a slow moving, hard, flat-faced bullet that plowed along through tough hide, muscle and bone and kept going in a straight line. They also damaged less meat.
I'd suspect that the same style bullet in the fairly slow moving 7.62x39 would behave similarly, and be good for close range shooting at tough animals.