This is a pretty good video on various gun storage solutions from a guy that breaks into places for a living. It's kind long at just over an hour, but lots of solid info.
He goes into this - you base your solution on a threat model - smash and grab, professional, toddler, teenagers, etc. Also a bit about fire rating and water damage. A bit about monitoring as well.
Plus a decnet amount of actually breaking into the various safes, security containers, etc.