I bought a set of storage lockers from a used furniture store. these are the kind of lockers we had in high school. About 18" wide with a top shelf. There are four lockers to a set. Cost $100. I use the top shelves to store handguns (arranged by caliber). 22 & 25 in one, 32 and 380 in one, 38 and 9mm in one and 44-45 in the other. Rifles are stacked in the main lockers.
A set of 4 paddlelocks (all same key) makes it easy to get in, but since lockers are lag bolted to wall joists, not easy to break into or steal.
I have seen the gun cabinets sold at CT. They are flimsy compared to these school-type lockers. You might want to look to see if your local busienss furnature dealer has any used steel lockers. My chair at the loading bench is a nice office chair on castors that cost about $35 used.