I am currently stationed in an NFA friendly state and live in the barracks on base. I cannot keep weapons on base so I keep all of mine in a storage unit off base. I am thinking of possibly sbr'ing a lower on a form 1 and am wondering if this is possible? Would I notify the civilian chief of police of where the base is located or the military police? Is there any issues with listing my address as the barracks if these items cannot be kept here? I am just feeling out this idea and if it will cause too much trouble, I'll just stick with using a brace for my build.

Don't know the answer to all the possible issues.... but that is why I have yet to bother with NFA because of all the issues with frequent moves, TDY, deployments, and overseas short or long tours.   You have to rent storage or have a trusted place for these items and for ammo...you cant store them in the .gov supplied storage.   I have probably $5K in ammo that I may never see again if the individual dies or moves that is storing it for me.

you can also store NFA items in a safe deposit box if you are PCS'd to a state that prohibits NFA.
https://www.atf.gov/firearms/qa/if-individual-changing-his-or-her-state-residence-and-individuals-application-transport

While I have never owned NFA items while living in the barracks, the Form 1 lists Mailing address--barracks address.
I would send the notification to the civilian CLEO--but that is me.

I would just notify the NFA branch that the item is stored in a different location with a 5320.20 after the form one is approved.
https://johnpierceesq.com/what-do-i-need-to-do-regarding-my-nfa-trust-when-i-move/

Unless you plan on making a career in the military (on active duty), I wouldn't bother with SBRs until you are out. Silencers- perhaps.

That was my thinking as well. It just seems too difficult to constantly do the change of address all the time. I do currently own a suppressor I got before entering the military but they are a different story. The quick turn around for form 1’s is so tempting though

I always used my "home" address (TX) when I was on active duty. Everything I purchased I did with civilian paperwork (DL or CHL).

I spent 24 years on active duty, I have multiple SBR's and suppressors and I never had a problem.

SBA3. I will never SBR again.

Retired Navy Chief Hospital Corpsman (20 years) here.  Establish a reputation for creditability and you may be surprised what you can do.  I had NFA (full auto) items at Camp Lejeune NC (Marine Corps base), with the Army (Navy rep at the Army run AFEES in Indianapolis), on my last ship (LY Spear AS36), and finally NAS Pensacola, then I retired.

The only "weird" thing was a couple of days after reporting aboard Camp Lejeune, I was told to report to the Provost Marshall's office.  There an ATF agent met me and said if the word gets out that you have machine guns, someone might offer to sell you stolen ammo.  Here's my card; if that happens, call me, I'm investigating stolen government ammo.  When I did the form for moving MG's from Indiana to NC, the Camp Lejeune area ATF agent was notified by ATF.  No one ever offered to sell me stolen ammo.

But a lot of "neat" things happened:  Carpenters on my ship made a wood crate for my M1917A1 BMG.  Rifle Range Marines supplied .45 ammo (to be shot on base at their thousand inch range) if they could shoot a couple of mags through the Thompson.  I was given 24/7 access to the 2nd FSSG, 2nd Medical Bn armory to store and have access to my guns if I wanted to take them out on the weekend; in turn I was made an alternate armorer for issuing and taking in weapons if our regular 2 Marine armorers were not present (they liked that...made it easier for them to be on liberty or leave).  I got to take out Marines and Corpsmen in my Medical Battalion and shoot some of our quarterly training ammo, that up to the time I reported in never got used...nobody wanted to fool with it.  Got to take a Marine course in inspection and repair of shoulder fired weapons.  Formed a rifle and pistol team for the Medical Battalion.  Told the Army I had to re-qualify each year with a 45 pistol to keep my expert pistol ribbon/medal (at that time if you qualified expert 3 years in a row, expert was made permanent for you), so they sent me to Fort Benjamin Harrison to qualify when the MP's did their qualifying each year.

I'm AD and have suppressors and SBR's.  Moving to an unfriendly state is always a concern, but you just have to have a plan in place, like a family care plan for your firearms.  Ive been lucky so far with GA, FL, CO, and TX for duty stations.  My luck may run out soon, and I may have to take a trip up to my dads to move some stuff for a while.