The US held three series of pistol trials beginning in the late 1970s to find a replacement for the venerable M1911 handgun. H&K was a participant in all three - in the first the entered a P9 and a VP-70, both of which were rejected. In the second series, they entered the P7A10 - a single-stack P7 pistol with an extended 10-round magazine to meet US Army minimum capacity requirements. This second trial also ended without a winner, and H&K further developed the P7 to enter into the third and final set of trials as the P7A13. This model introduced the first significant changes to the P7 design - a double-stack magazine holding 13 rounds of 9mm, a lever magazine release located behind the trigger, and a plastic heat shield to ameliorate the heating of the gun's gas piston.

Ultimately, some 30 examples of this design were made but they failed to win the trials. Regardless of the gun's merits, it was almost a foregone conclusion that the P7 would not be chosen, as the gun cost substantially more than many other competitors, including the Beretta M92 that was selected as the new M9 pistol. Instead, H&K used the A13 developments in a new series of commercial and police pistols, the P7M8 and P7M13.