I used to do that in MW2. On a good day I could go 22-8 with a M9 in TDM. A buddy and I also used to do that in SnD in MW2. It was really fun and challenging. I don't think I could do as well in MW3 since pistols require 3 shots to kill instead of 2 in MW2 with stopping power. I would say 14-18 isn't bad considering you used pistols only. Did you akimbo? I personally like to be able to aim, so I run extended mags or silencer.
I assume you're running core.
I can do rather well with the revolvers on core, but the rest is meh. For core I would say thats decent for pistols only. If that was HC then not really that good.
When I feel like pistols I run HC. Just so much fun to see people get pissed off when you kill them with 1 well placed shot while they pray and spray. Then yell "aimbot" or "hacker".
I've been using pistol since day one of mw3 and going postive is tricky. the low powered one's (usp, five seven, p99) are the better one for mid range the revolers are better for close range and at point blank nothing beats the deagle. Having the right gun for the right sitution in the right map is almost impossible to get right 70% of the time nevermind 100%.
going -4 when you you're going up against smg's, ar's or shotguns isn't too bad.
I'm a big pistol fan. I would say even is a great score. Obviously if I'm cautious I can go positive using pistols, but most of my good games are going even.
I really like this setup for pistol:
Usas (sprint boost)
Five Seven, suppressor or tactical knife
Scavenger (free tknives)
Just sort of a fun class to run around with.
Five Seven is my favourite pistol though. Low recoil plus big magazine, so I can lay into the trigger.