Sydney Vail, M.D.From Sydney Vail, M.D.Weapons9mm vs. .40 CaliberThe FBI announced it was planning to swap out the .40 S and W pistols and ammunition now used by its agents and replace them with 9mm pistols and ammo. It's time to look at the real-world performance of 9mm and .40 S and W rounds in terms of wound ballistics.January 22, 2016Page 1 of 1