title answers it all ive done double exp wont help out by alot ive seen people at the rank of 52 or higger with just like 12 matchmaking matches and 82 spartan ops mission whats the secret
They are idling in Spartan Ops and using Double XP.
It’s boosting and to me, is considered cheating and I hope 343 will take action against it(hopefully).
Hehehe, the secret is that if you play Spartan Ops Online, you will get anywhere from 4000-5900XP for just one spartan ops chapter. Which takes like 7-12 minutes yo complete. And by playing online I mean that you have to search for other players in the lobby, and not set up a game yourself. Because then it won’t give you as much XP 
LOL that expalin why ive seen lvl 55 or higher and have like 80+ spart ops mission completed and only like 10+ matchmaking