A gun safe must be secure and offer protection from theft and fire. If you are handy you can build one on your own. By following these steps, you will have a sturdy metal gun safe in which to store your weapons.
Purchase a used wall locker or wardrobe unit. You may be able to find one at a local flea market or resale store. You can also purchase them through government surplus auctions (GSAs). A particularly useful style that can be purchased through a GSA is a double-wide unit of the type used in military barracks.
Spot weld all of the seams in the locker/wardrobe unit. This will keep a thief or other unauthorized person from taking the gun safe apart to get to the guns.
Weld hasps at the top, middle and bottom of the door. These will be used to lock the gun safe with heavy-duty padlocks. You must install multiple hasps and locate them at the top, middle and bottom. Otherwise, someone might be able to pry open the door and gain access to the guns inside.
If the locker/wardrobe does not already contain appropriate hooks, hangers, shelves and drawers, install your own. Configure them in a way that allows you to store your guns and related items. Shotguns and rifles can be hung, while shelving can be used for handguns. Ammunition and cleaning supplies can go inside drawers.