Go into a team tactical lobby , make sure it is demolition or domination , once spawned it , quickly check the scoreboard to see if you are the first one with a 4 ping bar , If so everyone will kill themselves with a Semtex , Grenade etc if you see some red numbers come up once killed , do it 3 times and it should show you're level 50 , if you are not host simply wait till a host migration happens and check if you are host ,leave the game and it should stick , if you leave without being host it will not stick, it does not also stick if you wait till the end of the match , and also sometimes it may not work when you get into a game just simply back out and try again.