In case anyone is interested the amount of XP required for each rank is as following:
Private Second Class - 500XP
Private First Class - 1,250XP
Specialist - 2,500XP
Lance Corporal - 5,000XP
Corporal - 10,000XP
Sergeant - 15,000XP
Staff Sergeant - 20,000XP
Gunnery Sergeant - 30,000XP
Sergeant First Class - 40,000XP
Master Sergeant - 50,000XP
Senior Master Sergeant - 70,000XP
First Sergeant - 90,000XP
Sergeant Major - 110,000XP
Warrant Officer - 140,000XP
Second Lieutenant - 170,000XP
First Lieutenant - 200,000XP
Captain - 235,000XP
Major - 270,000XP
Lieutenant Colonel - 310,000XP
Colonel - 350,000XP
Elite - 400,000XP