I have always used Pelican cases for delicate dart guns in Africa. Thousands of miles bashing around in the back of the pickup, terrible to nonexistent roads, people sitting on it or dropping heavy spare tires on it, stuffed under bleeding carcasses (bait), etc. etc.. Africa is tough on gear, but I have never had any damage, nor dust or moisture get into the case. They make a shorter one for a broken down rifle or shotgun, as well as a long one with wheels for full size rifles. Downside is that they are heavy.

When travelling with a rifle in a full length aluminum case, I put that in a snowboard travel bag, which disguises it well.