Not an altoids tin, but speaking of the NAA pistol...

Someone made a bicycle rifle out of one, and to be honest I haven't seen anything else out there as compact (as far as pack rifles go) unless it was a single shot... and since the pistols are available in .22 Magnum as well, it puts it in a different class altogether.

As long as you had good sights, it would be a great squirrel getter!