I have several friends who travel exclusively in a large-size Pelican case, foregoing the "locked case inside of regular luggage" routine. One of the 1600 series is probably enough for the average traveller in addition to a single carry-on. There's nothing that says the ONLY thing that can go in your gun-case is a gun. If your locked firearms hard-side also happens to contain your sock and shirts, the TSA still can't open it.
I typically travel with 2 small Pelican cases locked together inside my regular soft-side checked luggage. One case contains the firearm and magazines, and the other ammo. I double-lock the cases and then lock them together through the handle with a cable.
I have a super-cheap Flambeau that I can squeeze 3 rifles in and put 4 locks on it and say a prayer... 4 separate trips with no issues.
The TSA has never failed to search my soft-size luggage when I travel with a firearm inside it in a hard-case, but I've never had a single issue either. I'm probably gonna splurge for a big Pelican for my birthday.
I take it back... one TSA guy at the scanner refused to believe that my Winchester white-box 100pk's and bulk .22lr packs came with all the ammo just loose in the box... I had to Google and show him an image and he still wasn't going for it. Luck was with me as the guy he called from the back was a shooter and laughed at him (gave me a wink) and it was all good.