[Firehouse]

Hey, Tom. OK, I'll be the guinea pig. In fact I've already done it; I have been struck by a falling bullet: no harm done. Think about it for a moment - don't worry about what grandpa or Dr Ruth or some other internet wannabe "expert" says - just think about it. Bullets are small; yes they're lead, but they're small. The free-fall velocity of a spent round isn't substantially different than however hard you can throw it. Can you throw a small lead bullet hard enough to hurt someone? Well, if you hit them in the eye or teeth, maybe. If you throw it and hit them in the back they'll feel it - maybe it will sting - but you can't kill anyone that way.
Someone else made the point about arrows. You can fire a magazine of bullets into the air and if the spent rounds come down in a group of enemy soldiers it will not do substantial harm. But if you fire a sheath of arrows into the air and they come down on top of the enemy they will wreak havoc. Why? Because the arrowheads are sharp, and the shaft is designed to ensure the arrows strike point-first. in analogy: you can throw a knife, or you can throw a small rock. I'll take my chances with the rock.