It's an older home so the walls are not drywall but wooden lath and plaster. Not that that is any more secure. The inside of the closet is lined with wood paneling that was common back in the 50's. So, it would be a little tougher to kick through than just two layers of drywall but it's nothing a sawzall couldn't get through. That said, I'm not trying to make it into an impenetrable vault. Visitors in my home are not going to try to kick in walls to get into the closet. I'm just trying to keep it simple and secure enough to keep out kids and visitors.
I guess my reason for posting is twofold. Is my plan for the door reasonable or am I missing something obvious? I'm not going to spend a ton of money when we may not even stay here for many more years. Secondly, I was looking for ideas to spiff up the inside to make it gun friendly.