What were you using?
A job box would be great for a temporary low cost solution, and disguising it isn't a bad idea.
Without going into too much, a TL30x6 is the best you can get (there's better but it's not necessary, over-overkill for our applications). Original's largest one comes with three different interiors including one for firearms. Uses a combo and a key. It's $11,000 but you can get a scratch and dent or whatever for $5000. They even sell the matching paint to fix the scratch! Find a large dealer, and negotiate with 'em. Be patient, may take a little bit to get the one you want for the price you want. But best you can get will be the largest Original TL30x6 vault with dual locks. It's a 3 ton monster. You'll need a slab but the installers are usually really good at getting it how you want it. If your apartment is a slab, you could get that now and just move it when you move. Moving 'em are a bit costly, something I'll have to do when I move, but you won't find a better gunsafe, period.
But with the cost of the tool box only being $400, and if the thief doesn't know it has firearms in it, it could be a good investment and you could get an appropriate vault when you move and still have the lock box to use for tools or other items. The lockbox will be less than the cost of moving the vault if you get that first.
Don't know what your rifles cost, but I couldn't leave the house when all I had was a stackon when I moved. I was constantly worried about it. When I got the current vault (technically it's not a safe but a vault) it doesn't cross my mind. But I'm gonna have to move in about a year and cost of moving those will be a bitch. I also have to find a house suitable for those.
You can also stash them in the attic if you have one. In an apartment, nobody looks up there and it's a great hiding place until you move and it doesn't cost anything. May be able to bag 'em and hide 'em under insulation. Installing alarms, I found a guy's entire NFA collection in the attic, I'm talking several WW2 belt fed MG's, rare full auto rifles, a suppressed Uzi, all sorts of stuff. You'd never know he had any of it --unless you went in his attic like me, to run wires for his alarm.
Just my .02.