I have used the Kolpin gunboot (with lock) on an overseas hunting trip, and on several U.S. flights. It came through fine every time. I did wrap it with tape, to provide extra protection on the overseas trip.
The aluminum cases used by others on the overseas trip were all damaged in some way. I suspect the airline handlers were put off by the much heavier weight of the aluminum cases and threw them around. The Kolpin case and rifle weighed much less, so it was apparently handled instead of thrown. (No guarantee that will happen every time, however.)
I have one of the heavy-duty aluminum cases, and wheels certainly sound appealing.
It's always a good idea to check the latest rules and regulations of the airline (and country) involved in your trip.