I DID NOT FIND OR MAKE THIS I HAVE SIMPLY PASSED ON A GOOD TIP TO HELP YOU IN GAMES

Get 2 Choppers guns for 1 extra kill - As far as i know this would only work on games E.g. Round switching or so.

Ok so on your first round of the game beginning use Hardline meaning one less kill for your kill streaks you have on at that current time.

Example I have currently got Chopper gun on as a 9 Kill streak. But i am using Hardline at this current stage of the game meaning 8 kills for the Chopper gunner. After screaming and shouting at the game i would reach my 8 Kill steak and a nice chopper gunner. I know how tempting it can be to use it But stay calm and find yourself a neat spot to sit and camp for the rest of the game. ok when switching sides you should still be on your 8 kill streak. Switch your class to a class without hardline on, go shoot a noob or so bringing you to your 9 kill streak. Having no hardline on this will mean you will receive a extra chopper gunner for one kill

This works with any Kill streak you desire. I find this works best with Demolition.