Space is only a starting point. There are several other considerations when buying a gun safe.
Dial vs. Electronic Lock: A dial or combination lock allows access when the proper numbers are entered in the proper order. This mechanism stands up over time and requires no maintenance. On the downside, the dial lock takes longer to open than an electronic lock and doesn't automatically lock when the safe door closes. Electronic locks, including keypad and fingerprint (biometric) locks, allow for faster, easier access and lock automatically, but, as with all electronic devices, they don't last forever, their parts can simply fail, and regular battery changes are required [source: 6mmBR].
Steel Strength: The walls and door of a safe are made of steel, and the thicker steel, the harder it is to drill into. Thickness is measured in gauge, and the smaller the gauge, the thicker the steel. A safe with 10-gauge walls is more secure than one with 14-gauge walls [source: 6mmBR].
Weight: Large gun safes can range from hundreds to thousands of pounds. To discourage thieves with dollies, 750 pounds (340 kilograms) empty is a good minimum. Ideally, they should also be bolted to the floor or wall [source: 6mmBR].
Fire Protection: Some say fire is a greater danger than theft for gun owners. House fires can reach 1,200 Fahrenheit (650 Celsius) in 10 minutes, and some guns melt at 800 F (425 C), so fire protection is important. A fire-resistant safe has a thin, insulating liner and offers minimal protection against extended exposure to heat. A UL-rated fireproof safe is better. It is often equipped with more substantial sheetrock or ceramic panels that can keep the interior below 350 F (175 C) for 15 minutes to 4 hours, depending on model [source: 6mmBR].
Some other considerations:
- Hinges -- Outside-mounted hinges let the safe door open wider for easier access, but they also give thieves a chance to saw them off. If the safe door has enough locking bolts, though, the door will stay on without the hinges [source: 6mmBR].
- Water protection -- A water-resistant safe can keep the interior dry in standing water, while a waterproof safe can keep it dry when tossed in a swimming pool [source: Tractor Supply Co].
- Extras -- Gun safes can be outfitted with hidden compartments, dehumidifiers, camouflage fronts (for blending into bookshelves, walls or drawers), lighting, additional drawers and pockets.