Just wandering through the old thread on the L-42A1 transit case and saw a bit about the difficulty of finding catches and hinges, etc.
Over the years I have moved, stacked, built and repaired a few different transit cases, also known in "show-biz" as "flight" or "road" cases. Usually made from structural (water-resistant) plywood, they are also equipped with robust metal catches, hinges, edging and corners and usually, wheels.
Most of the better ones use "hardware" from a company like "Penn Fabrications", who can be found here:
Flight Case Hardware | Flight Case & 19 Inch Superstore | Penn Elcom Online
Check out your local rock 'n roll band, theatre, or film / TV crew for the 3-D experience. Cases for electronic keyboards and bass guitars are a good model for a rifle case.