and if it doesn't penetrate with one shot, it will dent it. some armor used to be sold with a dent to show that it survived a round. but denting will weaken the metal too. that was with more primitive guns. modern small calibur travels at a sufficient speed that would penetrate most metal armor. plus, chain mail tends to be the standard. even leather is high class armor in those days. perhaps heavy armory would survive, but not the armor piercing rounds that would be in the machine guns. those bullets are thick and long.