Our military hands M-16s and a heck of a lot more to 18 year olds every day of the week.
I was a Correction Officer for NY State. After weapons training, we were also Peace Officers. I was around 34 when I finally went to the academy after having already been on the job for almost a year. During that first year I couldn’t do any jobs that required carrying a weapon, until I had weapons training at the academy. There were a few male trainees who were between 3-6 months from their 20th birthday, and although they were allowed to attend the academy, and go through weapons training, they weren’t allowed to carry on the job until they’d reached their 20th birthday. I had to qualify with the AR-15, and the other weapons issued by the department every year, and although I never had any problem qualifying for the 25 years I was a Peace Officer, I never enjoyed it. I could have bought and carried a weapon on my badge, but never did. It was just something I didn’t care to do.