Ok, you guys are starting to convince me. Next time I'm in a sporting goods store I'll see what kinds of tackle boxes they have that could be easily modified, and are decently priced. This way, I will have more time to work on the ten rockets I am currently building.
The thing is ... no matter how large your range box is (or how large your collection of range boxes is), you'll quicky find that you need a larger one (or a few more of them).
I actually use a bunch of those plastic Stanley toolboxes that you can get at a department store or home improvement store for under $10 each. They are inexpensive, of a convenient size, and stackable. I have one that contains supplies for a model rocket launch; one with stuff for assembling reloads; one with sun screen, bug repellant, hand wipes, and other supplies; one with general toolsl; etc. Each is (or is supposed to be) labelled so I can quickly grab the right one.
At home, I also have ones with drill bits and saw blades; one with rotary tool stuff; one with electronics tools and parts; and so on. It makes it easy to grab just what I need for a specific job.
For model rocket motors I have one of the flat, compartmentized Stanley boxes that others have mentioned. I bought a big shotgun case for my motor casings, but am finding it a bit unwieldy and not very well made (it has those plastic catches that come off too easily). My reloads are in a metal, magazine-like tool box at home. I take what I need to a launch in one of the Stanley tool boxes.
The toolboxes I use don't have many individual compartments, so things aren't as organized within a box as much as I would like. For that reason, I carry small parts in a small, compartmented box I got from Harbor Freight. The parts box is similar to the Stanely box that holds my model rocket motors, but smaller.
A custom-built range box would be cool because you could design it specifically to your needs. But, as I joked above, your needs will change. And, I don't think you could easily build anything as light as the commercially available plastic boxes. Check out the tool aisle and the sporting goods sections of a department store and you'll find a wide assortment of tool and tackle boxes to choose from. Also, check Harbor Freight if you have a store near you. They have less of a selection, but the prices are pretty low.
-- Roger