45 H.P.

The 45 HP is also known as the 45 Auto Short, having a case that is 1mm shorter than a standard 45 ACP. It was developed because of restrictive rules on shooters in many countries making it illegal for civilians to own semi-automatic pistols in military chamberings such as the .45 ACP. The 45 HP cannot be fired in a standard 45 ACP because of headspacing issues.