You can get a case at Wal-Mart pretty cheap. I have a Rifle Case and a Pistol Case from Wal-Mart. Both have flown just fine.
Watch out though for incompetents. I flew from Pensacola to Miami no problem. I just declared it, got the tag, etc...
The Woman in Fort Lauderdale didn't have a clue how to tell if a gun was loaded. But was generally nice about it.
I ran into a woman and a man in Jacksonville that had sticks up their asses. The one woman actually question me as to why I owned a gun. The guy offered me $80 for my AR-15. I almost felt like telling him he was crazy. But, I just said no thanks. The rest of the people at JAX were cool. It was just those 2 that seemes to have a stick up their ass.
As far as it goes, make sure anything that looks like a gun to some idiot is in the locked case. I got alot of shit once for carrying my Lower, Bolt Carrier, Charging Handle, and Spare Parts in a locked Pistol Case, and the Upper minus the Bolt Carrier in a locked suitcase. The guy seemed convinced it (The Upper) was a Machine Gun. I had to explain to him that it was a Semi-Automatic and perfectly legal.
But, as long as you put your rifles, unloaded in a Rifle Case, you should be fine. I have never had a problem using a Dedicated Rifle Case. I only run into problems when trying to use something that isn't a Dedicated Rifle Case, even if it is hardsided and is locked.
1) Declare your Firearms at any Checkpoints before the Counter.
2) Declare Your Firearm At The Counter.
3) Sign The Orange Tag and Put it inside the case.
4) Show the woman it isn't loaded (up request) and don't scare her.
5) Relock the case and affix Luggage Tag.
6) Your Ready To Go.
Carrying ammo. can be a lot of shit. But, I always carry ammo. with me. Especially when I fly into Miami. I get in the Car, load my Gun and drive home. I figure if I take a wrong turn and end up in Overtown I will be prepared.