Let’s cut thought the myths.
The 9mm will serve you perfect. The .40 will serve you perfect. The .45ACP will serve you perfect. It's all how you use and shoot the pistol. I recommend to people shoot what your most accurate with and practice a lot. It's also good to take classes on how to use your pistol.
A pistol is a tool and no matter how good your tool is, you still need to know how to use it. I often tell people if you had one tool that could take apart and put back a motor could you do it. No, they need training on how to use that tool. It's the same with a pistol. Every one can pull a trigger, but it takes years to develop combat skills or defense skills and to maintain those skills.
If I were back in the Marines and was heading into combat I would have liked to take my HK Tactical .45 with 12 rounds ball ammo. I can’t walk around town with a Tactical strapped to the side of my leg and ball ammo that over penetrates. I need to conceal and carry everyday. It needs to be light and easy to shoot. The ammo needs to fragmate and stop in the target. I want the ammo to hit a barrier and stop. I am not law enforcement and don’t need to shoot through glass or doors or any other barrier. The pistol is last resort defensive only, a family protector.
The HKP2000SK:
The HK P2000SK is a defensive pistol. Although, the HK P2000SK has proven to be as accurate as most full size pistols. This leads me to the velocity stripping barrel length. This is a blown out of per portion. Yes, shorter barrels do take away some velocity, but not as much as people are led to believe.
Here is Remington’s ballistics.
They used a 4" barrel
Golden Saber 124 muzzle 1125 50' 1031
Golden Saber 124 +p muzzle 1180 50' 1089
Hk P2000SK
Velocity tested 15'
Golden Saber 124 15' 1060
Golden Saber 124 +p 15' 1087
I believe that the Velocities at 15' are probably going to be in the same range. Even the difference from Remington’s muzzle velocity and test results at 15' are not far off and will not make much of a difference.