In 2008 I flew with Delta and Air Alaska and had my guns in a lockable golf club case with no issue. Of course, since then, airlines are abusing and nickel and dimeing customers more so who knows if that would "fly" today.
I doubt, but could be wrong, that a Tuffpak would meet the current dimension restrictions for many airlines for standard baggage. If it doesn't meet standard baggage dimensions, you may find the extra charges for the various legs of your travel may more than pay for a new travel gun case.
