I have global entry which include pre-check. Most of it is done online. It took maybe 6 months to complete but it wasn't difficult or require a lot of effort.
From the Code of Federal Regulations 1540.11c 2 iv - The container in which it is carried is locked, and only the passenger retains the key or combination. By using a TSA lock you are breaking this regulation. By nature someone other than yourself has a key to TSA locks. Additionally you must declare your firearm is unloaded per the same regulations. It's a long shot but someone else could load it and you'd be responsible.
I've never seen a quality TSA lock. Maybe they're out there but I've never seen them. A buddy of mine flew through Houston and was told by the TSA agent that he needed to replace his locks before they would clear them because "he could break the locks using 2 wrenches". I don't know who carries around wrenches but he had to get an uber and get to a store to buy new locks before he missed his connecting flight. These were not TSA locks but master locks with a 1/4" shackle.
There is better chance than not that using a TSA lock or surrendering your key/combo in Argentina you will be welcomed to an empty rifle case when once you are back in the states.
I've flown over 2 dozen times with a rifle, both domestically and internationally to 6 different countries. I'm not in a position to jeopardize my equipment or my freedom. I offered fingers my suggestions based on personal experience. If you find this ridiculous and silly then so be it.
