Re: Which luggage locks
I fly several times each year to Europe and on almost every trip I have either a rifle or shotgun with me, plus ammo packed separately.
The first time I went I called the airline and advised them ahead of time that I would be checking a rifle, which by the way is a good idea since it seems to make check-in a little easier since the gate personnel will see that noted in your reservation when they pull up your reservation. I was told to use TSA locks and so I did. Once checked in I was walked over to TSA to have them inspect the contents. TSA does that and lectures me to never use TSA locks since only I should be able to unlock/open the case.
Next time I did the same advance notice and showed up with big Master padlocks, checked in and went to TSA (same airport and airline FYI) where I was lectured again, this time for NOT using TSA locks. Go figure.
This seems to be the pattern so I've gotten in the habit of bringing both types of locks so when I get lectured by TSA I can swap to whatever lock they want that day.
The other interesting thing that happens on almost every trip, regardless of the locks, is that I generally find that all my luggage has been hand searched with little notes from either TSA and/or German Customs in each bag plus there is one round of each ammo type missing. Never more than one round but almost always one. Weird.