I use a couple of the HF Apache boxes w/do-it-yourself foam blocks. My problem has been that if it's a tool or item (cameras in my case) that gets removed/replaced often, the foam rolls over on the edges and then eventually gets in the way. You have to peel off the damaged block.

The Apaches would be great if you only removed something from it 1-2x per year.

Or, at least this has been my experience. The case itself is wonderful.

As far as the OP gun case example, I'd guess that thing would weigh 100# loaded? I doubt the handle would stand it.