Mw2 PSN, ACR one shot kills...?

Definitely sounds like a modded lobby, Ive joined quite a few on accident before. Usually they're just speed glitches, so everyone runs around at like 100mph. One time I joined a match where everything was an automatic weapon with unlimited ammo (even rocket launchers). I just recently noticed that my win streak is 72, which is impossible since I play 99% FFA.. so that had to have been from joining a modded lobby as well.