That's interesting, a friend of mine is a retired Ranger. He put in 30 years of service. He went to purchase a hand gun and it took a week to pass the NICS check. I'm a nobody and my NICS took less than 5 minutes.
When I retired after 21 years service I was delayed when purchasing firearms for close to 5 years. My employer ran a background on me when I was hired in '98 and it took well over 45 days to come back.
I have a theory as near as I can figure talking to a lot of people it was because I didn't have much of a paper trial.
I never lived in one state or country more than 3-1/2 years; always on base.
The only monthly bills were cable and phone.
My state of legal residence didn't require I renew my drivers license unless I was in state more than 30 days.
My license expired in '82 and never got a new one until '98.
My state of legal residence didn't require I fill out state income tax forms unless I was in state more than 30 days.
I always had my state of legal residence license plates since I could do it though the mail.
The company that ran the background check couldn't even verify that I even lived in Florida or North Carolina. My room mates were already there when I moved in so I just paid them cash for my 1/2 of the phone and cable.
My wife never had an issue with purchasing a firearm or any of her background checks anywhere we lived. I always thought that was interesting.