This wasn't by any chance someone called x_oTempTed_x?
I joined this guy, didn't seem like he was cheating, but did fire the MK14 like it was a machine gun and also very accurately- very quick trigger finger. As I joined the lobby people were already talking about his previous MOAB. I was on his team the next match and he got 37-0 with a MOAB in about 4 minutes.
He was talking through his microphone, running a very in-depth commentary about his profile stats and weapons, but his headset speaker was broken and he couldn't hear anyone else. I congratulated him on the match and he said "I can't hear you if you're calling me a noob". Kinda seemed like he had some sort of aspergers or something. Fantastic player but sounded like he was a bit demented, like he was playing a real war game and it really mattered or something and that he had to run a commentary even though he wasn't directly talking to anyone.
I can tell he wasn't cheating because when I played him I stopped him getting a MOAB countless times and managed to get him when other cheating people turn around and get me beforehand.