The two problems I try to avoid are shifting contents and skewing halves.
The Tuffpak and some other plastic cases do not hold guns securely without packing other materials in. That is just not a good idea in my experience. If I traveled with enough guns in takedown mode to fill one, that might be another story.
The briefcase style cases need to have some means like the Z cases above to lock the halves together in the correct plane. Otherwise, the hinges cannot take the skewing forces. The ridge that some makers such as Americase use is only of some assistance although their hardware tends to be superior to some.
Like some of the other hard to find items, Dan Walters cases are some I have found to be useful in the long term.
Almost any case will work better if you ship it in its box in my experience.
I have both the lighter and heavier metal cases mentioned by posters. All have worked for multiple trips including overseas. I don't pack more than two guns per case, I use a cover if available and I put the case in a cardboard or corrugated box.
I guess it is ever a trade off between weight and security but I have found that the more compact Americase products have stood up the best at a medium weight category. No holes or skewing has appeared yet.
