You might want to think about collapseable stocks or folding stocks.   Guns can take up a lot of space depending on the optics and accessories you put on them.    I’ve seen plenty of my friends go from 12 or 18 rifle safes to full size gun safes just because of the optics they had on rifles.   One thing they never advertise when you are shopping for a gun safe is what kind of rifles it will hold.  Cramming your guns in will only cause damage and make getting guns in and out a headache.   Instead of worrying about having to find a new gun safe, you might want to think about spending a few hundred bucks on changing the stocks of your military style weapons to something that can fold or collapse.

The M4 Carbine rifle is not only a fast and effective CQB weapon, but a very easy to manuever carbine inside a vehicle.   You can easily gain 30% more room in a gun safe by mounting guns on the wall of the safe if you can fit them and you probable will.  I’ve seen friends mount short carbines on the inside door of a safe just because they could.  If properly mounted, an AK with an Advanced Technology Stock side folder will probable mount right on the door and you may even be able to two if you can mount it properly.