Sear and Hammer has posted how he now stores his firearms. In a Rubbermaid box!
Then I found a note on the Intertubes somewhere about a guy who had his house broken into. All of the guns in his closet were stolen but the one in the toolbox at the back of his workbench was left behind.
I do not think it is a bad idea, but if it was me I would bolt to box into the wall .. I suppose it would not be any safer but I would feel better about it.
This method is security by obscurity and while it may work, if someone did find it and want to steal it, they would have it in a few minutes.