I have a 1984 Browning Half shelves Half long guns. It says 14 long guns, Removing scopes and bolt handles I have gotten 32 in there. (24"Dx30"Wx60"T, 700 pounds, no fire proofing!) Depending on your age and buying habits, I say a half & half works well, you will have important papers and jewelry that needs locked up also. If you immediately need more room buy a second safe (all long gun).
AS to fire proof. Read their rating carefully!! there is a huge difference between one hour at 750 degrees F and one hour at 1200 degrees F. Dad and I watched a sales video of Century's top of the line 1/4" wall, 5/16" door and jamb area, rated 1 hr./1200 *F, The one in the film was in an airport hanger office. A plane crashed into the fuel tank farm and that office was in burning Aviation Fuel for 9 hours. The safe in the office had the log books for 12 aircraft and 4 or 5 Weatherby rifles in it. The outside of the safe was burnt to bare steel, the dial was burnt off! Inside none of the paper work was scorched! Not one crack or check in the Weatherbys' high gloss finish and until they opened the safe there was no smoke smell! My dad had closed his business and needed the store 40 years of important papers, So he ordered the biggest safe for household use. It weighs around 1800 pounds (plus what's inside!) 30" deep by 80" or 88" tall and 46" wide (IT IS HUGE!) Dad's is set up with all shelves set for rows of briefcases. (about 48 or 50 of them).
If you buy one that is just a fancy High School Locker, that is how secure your gun and papers and cash and jewelry are. At my HS, I could get in any locker in about 20 seconds (no padlocks allowed), The office had everyone's combination and it took them 45 seconds or longer! If you lose your combination to one of the beasts, they have to be drilled to get in, or destroyed by cutting the back off (easier than the front!) DO NOT GET A 9V ELECTRONIC LOCK! You will be drilling it sooner than you think!
Ivan