I'm not sure. I see large safes inside of jewelry stores, but I can't remember having walked past any after hours that were small enough where you could see the jewelry from the outside. Either way, I bet the entire stock of jewelry or precious metals could fit inside two large duffel bags (not that they could be carried anywhere. That's not a lot of additional space needed to lock it all up at night.

Seems like a display case that can be secured to the floor/wall, and then the guns locked to the case would be the middle ground answer.