@freemo The 9mm would penetrate thin steel better as 45acp has really poor performance in penetration. German helmets with the funny insignia would be penetrated by 9mm and the 45acp would just leave a big ass dent with blunt force trauma.

22lr fired from a standard rifle at 100 yards was the standard for determining the maximum effective range of a round. That energy at 100 yards was deemed to be the least amount of energy that could kill. 22lr is still quite deadly considering that it's likely never going to be just a single round that hits.

9mm Parabelem, used against minorities since its introduction. A proud tradition that still exists to this day. 45ACP, designed to put people down with a single round back when men fought with bare fists. 10mm, The round that defeated the pistols it was fired from.