Probably depends where you're flying through. I have friends who brought back plenty of bullets.
Flying through moscow, they wouldn't let me on the plane with extra guitar strings, they thought I might use them as a garrote. But apparently they weren't concerned I'd actually take the strings off my guitar to do the same thing. Cuz, y'know, I might be an assassin, but there sare limits to just how paranoid you need to be, right?