If its not too late, i recommend trying the Kalt... Its not particularly hard hitting, but its accuracy and RoF are staggering, i cant count the number of people i've mowed down with it. Just line those head shots up, because you can, and pull that trigger fast and hard.
MP are more of a finisher, or to get out of a bind, like your in a hot firefight, and you go toe to toe with a guy and your main JUST ran out.... Their ability to kill single targets far exceeds that of the pistol, but pistol range and accuracy can take out multiple people with a single clip with alittle more concentration and setup, not good for toe to toe.... Also, the fact that you can use a knife means you can hammer out some pain too if people get too close. Just empty some rounds into them, and finish it with a knife melee.
For that kind of role, ive had more luck with the Sea Eagle (more power and accuracy and my personal favorite handgun) or Tokmak (higher fire rate; amazingly fast with rapid fire). The only area that I think the Kalt shines is its equip speed. If you accessorize it to maximize equip speed, you can pretty much start shooting the moment you push the weapon switch button.
If you like using pistols, i would suggest getting used to the Sea Eagle. It hits hard, has decent ammo (15 with extended mag), and is accurate. Can drop people with 3-5 shots at most ranges, even faster if you can headshot.
If you get good enough with the sea eagle where you don't miss much, you may want to move up to the Ritchie, but its very unforgiving if you do miss.