Depth is essential for rifles unless you are going to strip them of scopes, bipods etc. Which is such a faff. Shotgun cabinets might be the answer, if they aren't too deep but your rifles will be at an angle to fit, so you'll not get as many as you would guns in there of course. And you might need another safe to store ammo, but a normal rectangular house safe should do that.
Captain Kirk: "Space, the final frontier".