Yeah, well, when it comes to that, there hasn't been much advancement in technology. I mean, "it throws bits of metal at targets..." is a pretty basic thing to do.
Flintlock Rifles did that. Reloading was the only issue there. (Well, the delay between trigger pull and firing was also an issue.).
Hell, bows and crossbows do that too, and how long have they been around? Before the common usage of metal as the warhead, IIRC. (Flint anyone?).