What is a believable age for an Army Staff Sergeant?

I spent 12 years in the Army. An army ranger of 23 only makes sense if he's turning 24 within the next two months, and he just made E6 last month.

Let's see, a 17 year old high school graduate means he's turning 18 before October 1st.

If he ships out to OSUT at Ft. Benning in late June, he'll be 18 by the time he is done with AIT.

Jump School and RIP will take up the rest of that year. He will finish RIP just in time to go home for Christmas, and return as a new E2.

He will have to spend a few months in a ranger unit in a probation period, where he will probably make E3 before 19.

Soon, he will either spend 18 months at war, then go to Ranger School, or vice versa. He'll make E4 and E5 during that time.

He CANNOT make E6 without finishing the Warrior Leader Course (WLC), which is a month long.

Many rangers, green berets, and SEALs postpone a promotion because they would have to leave the elite unit due to no vacancy in that pay grade. Have you ever noticed that almost all low speed, ordinary units still tend to have E8s, E9s, and high ranking officers with Ranger tabs, Special Forces tabs, and master parachutist wings? These guys may have to wait to get back into the hardcore units where few slots are available for the high ranks. In the meantime, they still outclass the not so hardcore, and can occupy the top of those units.

You are thinking of some guys who have made E6 in 3-4 years. I have seen it happen, BUT these were not guys who went in at 17 or 18. These guys had two or more years of college, and went in at E3 to begin with, and Ranger School, if I recall, gives the same amount of points as two years of college.

A 17 year old only goes in at E3 with either 3 years of high school ROTC, or the Civil Air Patrol's Billy Mitchell Award. HOWEVER, unlike college credits, where the time in service and grade requirements are shortened, JROTC and CAP still need time in service requirements. That is why you will notice that a guy who entered as an E3 due to high school ROTC can still take about 2 years to make E4.

For your novel, I would suggest making him a 21 year old E5 at the beginning, and making him a 23 year old E6 near the end. Don't forget all of the courses your protagonist will need to complete in order for him to get promoted.

I went in at 18 and made E4 in 18 months, and E5 at 31 months when I was 2 months past my 21st birthday in the 82nd Airborne Division. Therefore, 20 year old E5s are common. Your character's E6 squad leader could get killed in action, and the young E5 may take over the squad, but they won't put that extra chevron on him. It will definately help him get it later though.

Since promotions beyond E5 will require an annual enlisted evaluation report, and troops compete Army wide, you won't see an E6 without at least one 3 year hash mark.

I would say 23 is kind of pushing it. When I was in the Marine Corps I saw E-6 after 4 to 6 years of service. So yeah pushing it but if the character you are writing about is super squared away hard charger then I would believe it. But also it would depend on the MOS. Some MOS's would never allow someone to rank up so fast.

A young SSgt would be around 24-25+ at the youngest, assuming meritorious promotions left and right. You're better off giving him Sgt and a squad leader billet if you want 21-23.

No thats to young, around 26-34.