I have no idea whether the term used at the time for sling ammunition was bullet, but even so, I can't imagine that being a selling point given the penetration power of human powered sling projectiles would have with regard to plate armor. Also, the sources I've seen were very clear to link it to the rise of guns on the battlefield.
Interesting. I didn't know there was that much controversy (albeit for earlier armor technology). I was assuming, so I guess I was luckily right through ignorance. ;)
