Well, My 2nd Lieutenant was legit(1.39 KDR) and My SSG(1.45 KDR) uses chams. Heres sort of a mini guide:
To level quickly you have to stay committed and you have to have skills. By skills I mean you need to have 2.0 KDR in each game or close. Heres how you do it:
1. Go to Spyhunt and find some people or friends to powerlevel with.
2. After maybe an hour, quit and go and Fireteam, Until you get bored.
3. Go to Killcreek and do Elimination Pro.
Thats all <_<