Not only is locking your gun luggage with a TSA lock not a good idea, it's illegal. Federal regs require that firearms be placed in a locked, hard sided container, to which only the owner (i.e. you) has the key or combination.Oh, and here's a comment made to me by the TSA guy there...he said that if I were going to lock the case, it had to have a TSA-approved lock. When I asked him what that was, he said it was a lock that allowed TSA employees to open the lock without knowing the code, via a special key. Yeah, right...like I'm going to trust random individuals to go rifling through my luggage. It's Masterlock for me and my gun luggage.
I've found it helpful to print out a copy of the TSA and airline rules and regs for flying with guns to show the dimwits at check-in.