Gun Room Ideas

I’m thinking about converting my office into a combined workspace and gun room. So far, I’ve installed a 2-inch-thick solid-core door with heavy-duty security hinges with 3½-inch screws, and a bar lock on the inside. I’m also planning to add riot glass to the windows.

Now I’m debating the next step: should I tear out the drywall and replace it with cement board, or is there a better option for reinforcing the walls?