Here's my take on the gun rack...
Well, I used your idea and modified it a bit to fit my needs. I thank you for this idea and I hope you don't mind.
Here's a link to the pics of my gun rack:
http://picasaweb.google.com/Mud4Brains/MyGunRack?feat=directlink
I made it a little wider to accommodate 5 guns instead of 4 as I'm building an AR-15 and will need the space. The rack is 3' wide inside the uprights (37 1/2" Overall Width) and 4' Overall Height. I also put a place on the end for my Cold Steel .625 Magnum Big Bore Blow gun, however I think once I mount the rack on the wall, it'll be difficult to get it in the hole. :banghead: I may install a riser of some sort on the rifle shelf so that I can use the hole to hold my slug barrel for my Mossberg.
In addition, I expanded the lower shelf to be 11" deep instead of 5 1/2". Also I think my shelf is a bit taller at 9 1/2". The lip on the front of the lower shelf is a piece of 1x2.
I stained the rack with Minwax Special Walnut. Being a prototype, I just used cheap pine from Home Depot, however I'd really like to make this rack again with oak.
For wall mounting, I intend to cut a 1x8 down to the rack's 37 1/2" width, then rip it right down the middle at a 45 degree angle. One half will mount on the rack with the point of the 45 out, and the other half will mount on the wall with the lower part of the angle on the wall side so all I'll have to do is lift the rack and hang it on the wall mounted board. We have a white board at work that is mounted this way and that white board weighs about 80lbs.