Assuming you're using cinderblocks reinforced with rebar and filled with concrete and maybe a steel plate roof topped with concrete sheetrock, you can make a very secure room. The only weak point would then be your door. Line the whole room with sheet rock and you buy some extra fire retardant capability.
As far as security, you guys should think along these lines:
1) This is being described as an armory, so it's "for show." This will inevitably lead to people knowing about it that shouldn't.
2) Friends now may not be friends later. Displaying your weapons in a room, who's location is known will backfire.
3) Friends now may be addicts later. I've seen colleagues homes burglarized by friends who came upon hard times (drugs) and found an easy target. Needless to say, using a drill, blowtorch and 10lb sledge may not undo my construction.
4) You're discussing this on a public forum, most likely with a screen name I can search and dig up more info on you. With VERY LITTLE effort, your IP address can be gathered from this site, leading to a little bit of homework and finding your address. Yes, it's easy.
5) You're taking risks by discussing it here, especially since you don't know who's reading. If you do a search for "hidden safe room" on google, you'll be shocked to see all of the projects people basically advertise.
Personally, if I'm creating such a room, I'm hypothetically creating it with the purpose of safeguarding my hypothetical safes. So IF you get into the room, there is NO leverage to bring a long enough crowbar in to pop the door, nor can you tip the safes over. Hypothetically speaking, of course.
But yes, safe rooms and hidden rooms are the shit. Just so long as they remain hidden until AFTER you sell your house. Wives seeking divorces or who are kidnapped are also great ways to lose everything you've amassed, so keep the combination to yourself. Seriously. You may just keep her alive by doing that as well.
Bill Paxton... the only person to be killed by the Alien, the Terminator, and the Predator.
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