store it in the armsroom. Only problem is the Commander has to know every time you draw it out, and have to coordinate with the armorer since you will probably be wanting to draw it out on weekends to go shooting. its a pain in the ass but to be honest it's the safest for you, climate control wise, and also physical security wise.
Storage units are broken into all the time, there would be a very tricky fight involved if it was stolen trying to get any insurance to replace it.
Leaving it at friends is a possiblity but not advised, after quite a few years working in nail salons around alot of Soldiers I have seen even the best friends assrape each other when money gets tight, and thats one legal battle that would be tough as well since its a firearm being left with friends and it's supposed to be registered on post anyway, and is you, the owner's, responsibility to secure it.
Not too long ago a good friend of mine that i was "on the trail" with lent a rifle and a pistol to what he felt was a good friend of his to go hunting in Georgia. The guy went hunting with his family and when he got back we all were busy training.........nail techs, and a couple weeks went by before my buddy asked when they can link up to get his guns back. well the guy ho hummed around, made excuses, delayed the link up etc etc. Come to find out the guy was going thru a divorce and was hard up for cash so he had pawned my buddies guns. Long story short after a huge clusterfuck and a huge ordeal with the police and reports and whatnot they finally tracked down the pistol and my buddy got it back, he has never gotten the rifle back.
so, a case worth 10K is not worth all that to you then by all means pay more money monthly for a storage facility, or leave it with "friends" but I personally would deal with the pain in the ass armsroom and have peace of mind
P.S. don't leave Alabama without making it over to Anniston to visit the CMP South store and buyin a Garand or ten
http://www.thecmp.org/Sales/stores.htm