For my trip I would be taking my FN PBR 308 as my hunting rifle, it was transported in a Pelican 1750 case. Case has 2 locations for locks. I didn't want to use the standard dinky little TSA locks you can buy at Walmart, Target etc, I wanted something a little more robust.
I ended up going with these:

I liked these for the thick solid looking shackle.
These were recommended to me by buddy who is a Captain for Southwest.
I flew from Orlando to Arizona, check in with American Airlines went smooth, I was taken to the TSA checkpoint to have them scan my luggage since it contained firearms. They scanned my stuff while I waited, then one of the TSA officers came out of the room and asked to speak to me. She said they had a problem with my locks. The shackle according to them was too long, it allowed them to open the case enough that they could touch my firearm, they were touching the scope, but whatever. She said they would let it go, but in future use a lock that didn't allow the case to opened enough to touch the firearm. I asked where is that written in the travel rules for firearms, she said it wasn't, but is something that they want. I said thank you for letting me know and I would remedy that in the future. My trip went off with no further hiccups.
So just putting this out there for anyone who plans to travel with a long firearm who has to deal with TSA in future. Use a TSA lock that doesn't allow your case to be opened enough to allow touching on your firearm.
SY