O.k., here is some info for you:
P7M8 (9mm)
8 rounds
Weight w/o mag - 1.75 lbs.
Weight w/loaded mag - 2.10 lbs.
Overall length - 6.73 in.
Height of pistol - 5.04 in.
Width of pistol - 1.14 in.
P7M13 (9mm)
13 rounds
Weight w/o mag - 1.87 lbs.
Weight w/loaded mag - 2.5 lbs.
Overall length - 6.90 in.
Height of pistol - 5.30 in.
Width of pistol - 1.30 in.
P7M10 (.40 S&W)
10 rounds
Weight w/o mag - 2.69 lbs.
Weight w/loaded mag - 3.39 lbs.
Overall length - 6.90 in.
Height of pistol - 5.68 in.
Width of pistol - 1.30 in.
As you can see the P7M10 is a noticably larger and heavier pistol when compared to the single stack 9mm. If you are in the Los Angeles area, I can point you to a store that has both the P7M8 and the P7M10... Hope the info helps!