Thanks for the photo, Pietro. That is very similar to what I had envisioned in the OP only smaller. I would only need room for 4 rifles max and maybe a corner for a handgun case. It would have to be at least as long as the one pictured because 91-30 Mosin's, Swede's and K-11's are all pretty long. Some others are not much shorter,
Rather than solid wood, I would probably use a good grade of exterior plywood and paint it for durability. This plus a cover like hporter shows would serve my purpose very well. Thanks to all.