The last of the P7 series to reach production was the P7M10. Introduced in 1991 as an offering for the then hot new .40 Smith & Wesson cartridge, the M10 was HK's first attempt to enter this market before the advent of the USP, completely designed around the new caliber which had the ambitious hope of standardizing pistol ammunition for the American law enforcement community, which up until that point could reach no consensus on the "best" caliber for police defensive pistol use.
The M10, like the M8 and M13 gets its name from the German, "Magazinkapazität" (Ma-kah-tsin kah-paht-si-tate), magazine capacity, 10 rounds.
The M10 during production enjoyed lukewarm sales at best, due to the reconstructed slide that added so much mass for the heavier recoiling cartridge. Informally dubbed the "water on the brain" P7, the heavier did much to destroy the sleek lines of the 9mm P7 series that still enjoys such great worldwide popularity.
But, controversially, it did not have to be. The very first prototype P7M10s had the traditional slide. The 1991 issue of the HK Sentinel catalog has two photographs of the P7M10 with the sleek slide. They are shown in the two photographs below.