I have a cabinet the size of a refrigerator made from 3/4" plywood I store ammo in. Some bulk reloads go in plastic coffee cans. Shotgun shells and bulk rifle ammo are in cases or ammo cans under my workbench on shelves.
Throw some loaded ammo in a fire and you will see that there is not any danger. Powder in thin metal cans will not build up enough pressure to explode. Storing powder and ammo in a safe could cause it to build enough pressure to really make a big bang. Using a safe might help keep ammo from being stolen but I am more concerned with a fire. Larry
Close to what I do.
Most of mine are stored in plastic tubs (with lids) in a spare closet.
Then the safes have a hundred rounds stored in them for each caliber.
If ever a fire...
Kids, wife, ammo, then safes, will be drug out in that order - if time.
Very little in the safe with the guns. A couple of loaded mags for my Mini 14 just in case a rifle is needed fast. Home defense gun is a 12G shot gun and that has a bandoleer close by.
Most others is in many GI ammo cans on a bunch of shelves. .22 bricks are on their own shelf, but they're not in cans!
I don't store a lot of loaded ammo, normally I load it as I need it so I may have a couple of thousand rounds lying around at any given time. For storage I use an old file cabinet in the gun room (just make sure to empty the loaded ammo from the front of the drawer first so it won't tip over if I pull the drawer all the way out )