I've gotten 6 kills in one round in Crossroads SEALs a couple of weeks ago. I cheated though, I had a buddy of mine spectating and I was on the phone with him. I felt so guilty by the 7th round, but hey I had a crap load of kills.
8 kills rats nest. I jus hid in a dark spot with 552 sd which makes this very hard 2 do and threw some nades got 3 kills, one stepped on a mine and the otha 4 jus ran around in circles clueless where i was.