Since you said soft lead and metal targets it's probably some of the lead flying back at you.
Sometimes the lead ball, when striking a metal plate won't mushroom and fly out to the sides.
It will form into a molten cup shape with the ball liquefying as it moves into the plate and forming the cup shaped blob with the lead moving back towards the shooter.
If your far enough away the returning lead will fall to the ground but if you close it might reach you.
This can be eliminated by having the metal plate at an angle so the splash doesn't come back in your direction.
While I'm writing, when I first saw the title of your topic I thought, "He's shooting at a thick wooden board and its the roundball that's flying back at him."
With a low power charge and a thick board, that's exactly what can happen.
The ball hits the board, deflecting it without actually penetrating it.
The board, not enjoying being clobbered by a flying ball returns the favor by using its deflected energy to throw the ball back where it came from, often nearly as fast as the ball was going when it hit the board. :shocked2:
More than a few shooters have been seriously hurt by this sort of thing.