More steel more better. Buy the most steel you can afford. More steel is more mass to move, more mass to heat up in a fire, and more physically secure (probably exponentially; I haven’t done the math) from all methods of breaching. About 14ga and thinner can be cut open with a circular saw like a can of tuna. 10ga or thinner steel can be pretty easily breached with an axe or usually just pried open. 8ga and thicker steel is pretty much axe-proof and is more difficult to bend by prying, but can be cut into with an angle grinder or quickly torched open. Stainless steel reinforcement or real concrete (both in very expensive safes) protect from torch attacks. Hardened steel plates over the front important bits protect from most drill attacks.

Construction is as important as materials. The design of the door and frame is huge in determining stiffness, and subsequently security from pry attacks. The more contact area between locking lugs and the door, the stiffer your frame. Look for a safe door whose locking lugs rest against a flat part of the frame, not directly against the thin edge of sheet steel. Door-to-Frame fit is probably the most important aspect of protecting against pry attacks. If an attacker can’t fit a tool between the frame and door, they can’t even start to pry anything. Locking lugs need to be BUILT CORRECTLY. Many safes have 100 giant active locking lugs that are then welded to shitty mild steel rod linkages inside the door, where you can’t see them. When pried those lugs are going to bend at the linkage and do nothing for you. Sometimes a safe company will cleverly advertise weak linkages as an advantage, because the linkages could break if the lock is forced in an attack… then you’re completely up shit creek, and need a locksmith to rebuild, or more likely replace, your door IF they can get in without destroying the safe. Just build/buy better locking mechanisms. Weld strength matters too, but this is generally harder to see and inspect for yourself. Cheaper safes have shallower, weaker welds that are closer to spot welds than full seam welds. Doors with exposed hinges aren’t weaker, but do allow you to open the door wider and usually let you remove the door for much easier moving. Even if you grind exposed hinges completely off, the door isn’t going anywhere.

Fire protection is tough, because it’s hard to find a rating that means anything. Ceramic blanket, TRUE concrete/refractories, and thick steel protect from fires as much as anything can…. eventually fire claims all. “Fireboard” and other forms of glorified drywall truly do nothing for protecting the contents of your safe. They are designed to prevent the spread of open flame in a structure by not being especially flammable, not to insulate an oven. Even proper fire safes might not protect your belongings in a total burn down, especially if the fire is allowed to burn itself out and smolders around your safe. Maybe you could get the fire department to soak the location of your safe to keep it from turning into a smelting furnace?

Now I’m not saying go buy a $10,000+ true SAFE (not a residential security container like most big metal boxes sold as gun safes) that’s built with inch thick plate steel, reinforced with stainless panels for torch resistance, hardened plates for drill resistance, concrete fill for fire/torth and breach resistance, and as much ceramic blanket as a kiln… Use this information to perform a no-bullshit risk assessment and determine the right amount of security for your situation. Personally I think it’s nuts to pay $1000, $2000, or even more for what’s essentially a very nicely painted thin sheet metal closet. I can turn your $1500 thin metal closet into nothing with a circular saw, pry bar, or axe. For my situation I want security from simple physical attacks, but if someone decides to lug around a torch (make sure they can’t get yours from the garage) or knows precisely where to drill to bypass your lock, they’re getting in one way or another.

Decide what’s right for you.