Is 22-23 too young to be an e6?

It depends a great deal on the person and situation. Some service members get E6 very early in their career due to technical prowess. They may not have to demonstrate mature leadership capability. Others have both the technical and leadership abilities normally found in slightly older, more experienced service members. At 23 a service member who joined at 17 has 6 years experience, but a college grad who joins at 22, instant E4, won’t have enough experience in a year or so to be an E6.

I saw early promoted officers move into positions of responsibility at the Squadron level before they had the needed experience. They stood on the shoulders of more experienced but lower ranking officers to succeed. If they were smart they knew it and retained some sense of humility. Many didn’t.

Is it too young, as in impossible? No.
Is it too young, as in effective? Usually, but not necessarily.

When I was enlisted, we had a 23 year old E-6 in our unit. He was very good at his job and I personally thought well deserving of early promotion. However, there are a lot of good leadership qualities that come from maturity and that only comes with time. Certain things you simply can't teach. I was personally a 20-year old E-5 and, while I was proud of my accomplishments, I didn't truly realize until years later that I was probably too young to actually be a Squad Leader.

For what it's worth, I was promoted to E-6 as an 11B40 in July 1973 at the age of 22 after a tour in Vietnam in 1970-71. I went on to attend OCS in the fall of '78 and was commissoned as an armor officer. I spent my last tour teaching at West Point and retired at age 40 as a major with a Ph.D. Bottom line: The army will let you "be all you can be." . . .