in my Air Force experience, the military gun ranges were not available for individual practice. If you were not showing up to get formal training or to qualify with the weapon with which you are required to be proficient, the only option for regular practice is a private range.
I think I've been on an Air Force range once in college ROTC, 2 more times for qualification while I was in a mobility billet (if you aren't subject to deployment, you aren't qualifying regularly), and one for the Excellent in Arms interbranch competition. That's over 4 years in college ROTC and 9-1/2 years active duty.
My qualifications were with the military .38. So, I practiced with a .357 Magnum using .38 Special +P ammo. A few coworkers and our spouses would meet at the nearby range and shoot for a couple of hours.
At least 2 coworkers/spouses were under 21.
"if you aren't subject to deployment, you aren't qualifying regularly"
I was mobility for most of my USAF service. so I had to qualify
regularly. M16. Y'all know what a pain it is to qualify as Security Police
with no practice? I did it, But I can shoot right or left handed from any position.
I grew up with guns. Obviously not in Hawaii.
BTW I fixed aircraft avionics and I wasn't an SP.
Nixon killed off all off hours use of the range. Saving money for taxpayers?
I entered the military at age 17.
Bought ammo as far back as I can remember.