What I've been hit with behind the firing line I wouldn't define as "shrapnel". It's usually jacketing material that comes back toward the shooter after the lead bullet splatters against the trap. Most of it is usually closer to the floor height, so don't wear open toed sandals.

I've also been hit by bullet splatter outside with a group shooting steel targets, so it's not unique to indoor ranges. I've been nicked in the face a couple of times by it. It's one of the reasons we wear safety glasses, right?