I would do 2 textures: one is the hole, and the other one is the blood stain.
The hole's tranparency is animeted on few frames. In fact, it becomes visible as soon as the bullet hits the body.
The blood stain can be more gradual, but not that much (like 10 frames).
For more effects, I would go with particules behind the body (where the bullet normally comes out).
Otherwise I don't see how you could do something more to achieve realism.
Bernard Lebel