x2 on what Gary said on printing their regs, especially if you want to put ammo in with the guns too.

I have an SKB pistol case that fits a couple of revolvers +/- and encore with a 15" barrel if put in diagonally. I've also used my SKB rifle case and a Pelican case. Regardless of what you buy make sure it can be locked with something other than the TSA-approved locks (like a pad lock) and don't expect the airlines to treat it nicely. They broke the spring-loaded handle on the end of my SKB rifle case, and I'm still not sure how as it lays flat unless you lift it up... Just like with optics, buy the best quality you can as regardless of the case type, it will not be treated nicely by the airline.

Also make sure the airline agents don't put a "firearm" label on the outside of the case as they're not supposed to, but some will try it...