I posted some of this on the Steam forums some days ago.
Honor level is increased playing as any class and obtained every match - along with Class EXP towards leveling your particular class. There are 6 Rank levels, and you need to fulfil a certain Honor level in order to progress - e.g. Honor level 80 is required, plus 5333 Class EXP to reach L5 Highly Decorated Rifleman (I have often reached the Class EXP requirement before the Honor level).
You unlock new weapons at certain Class levels, and upgrades through Kill Points.
Does that help?