Why is the mv300 tsa approved, yet the mv 500 is not? it's bigger, stronger, and more expensive????? - GunVault Microvault Portable Pistol Safe

I need to safely carry my weapon in my luggage on an airplane. I can't get a straight answer. Is the MV500 TSA approved as stored luggage (NOT CARRY ON). If it is, where is it in ? Should I have bought the cheaper, weaker, and smaller MV300 model? It's TSA approved. I don't want to get to the TSA lines and find out I can't take it. Then what do I do with it? I'm allowed to take it in a plastic case with locks on it. Makes no sense. I want to take the MV500 so I can secure my weapon in my hotel room. HELP!