I've condensed and altered this to better reflect what we've been doing. Dropped the warrant officers as frankly we don't use them and they're a bit confusing for the game structure.
There are two types of rank: Enlisted and officer. My understanding is that officer ranks require different training/schooling than your basic enlisted ranks. Pay grades are used to standardize pay and are not rank themselves. I am also removing some of the ones we simply aren't using and that haven't come up to simplify this a little as presumably the GAF streamlined a bit.
"Service members in pay grades E-1 through E-3 are usually either in some kind of training status or on their initial assignment. The training includes the basic training phase where recruits are immersed in military culture and values and are taught the core skills required by their service component. Basic training is followed by a specialized or advanced training phase that provides recruits with a specific area of expertise or concentration. In the Marines, this area is called a military occupational specialty (MOS) Leadership responsibility significantly increases in the mid-level enlisted ranks. This responsibility is given formal recognition by use of the term noncommissioned officer (NCO). A Marine corporal is considered a NCO rank."
Private, First Class. (PFC) Pay Grade: E3 (no pips)
Lance Corporal (LCpl) Pay Grade: E4 Corporal (CPL) Pay Grade: E5 (one pip)
Sergeant (Sgt) Pay Grade: E6 (two pips)
Staff Sergeant (SSgt) Pay Grade: E7 (three pips)
Sergeant Major (SgtMaj) Pay Grade: E9 (three pips)
Officer ranks outrank enlisted rank officers of the same or lower levels.
Cadet (student, not out of training)
Bailey's potential PC
Ensign, (entry level one pip)
Lieutenant, Senior Grade (two pips)
Lieutenant Commander (two pips)
Commander, Pay Grade O3 (three pips)
Captain (Capt.) Pay Grade: O4 (four pips)
Admiral (Col.) Pay Grade: O7 (five pips)
Avery's rank at the start of session 3
Major General (Maj. Gen.) Pay Grade: O9 (six pips)
General (Gen.) (three stars)
Commandant of the Marine Corps (five stars)