P-1s were designed for German Military cartridges which were hotter than any 9 mm cartridges offered by major U.S. manufacturers prior to +P offerings. That's why the standard relatively low recoil U.S. 9 mm cartridges were problematic in Lugers.

Be warned, P-38s and P-1s have the double action that Jeff Copper wrote so many bad things about. They are not the easiest DA/SA to fire the first shot accurately with. Many modern DA/SA automatics have a better double action pull. Also, there is a blind hole in the bottom of the rear sight for the fining pin safety plunger so only the front sight can be drifted for windage. Supposedly different height front sights were offered to sight in for elevation but good luck finding any.

However, they are an intriguing historical artifact with a reputation for good reliability and accuracy.