Q:  What is a P7 M10?

A:  The P7M10 was 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, "Magazinkapazitšt" (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.

Nickel P7M10 manufactured in 1991(KB), serial number 012

Nickel P7M10 manufactured in 1991(KB), serial number 012

Best photograph yet of the slim slide prototype P7M10, serial number 21-005. 
Now this would be a valuable collector!

The P7M10 slide was beefed up on insistence from German engineers who said that the 9mm slide would not hold up.  A former HK USA engineer named Paul Carroll claimed that the smaller slide was quite sufficient.  The Germans obviously won on the technical side, but Carroll seems to have won on the aesthetics side.

An interesting note about M10 magazines is their similarity to their higher priced cousins, the M13 magazines.  .40 caliber M10 magazines hold 13 rounds of 9mm ammunition and reportedly work just fine in 9mm M13s.

Available in nickel as well as traditional blue, the M10 production ceased with the advent of the 1994 Crime Bill, and the attendant decision to cease civilian sales of the M13 pistol at that time.

(Courtesy HKPRO)