I had a Pelican double rifle case (1750 if I remember correctly) for a while. 3 sheets of foam, trace the outline of your rifle and scope on middle sheet and cut it out. Gun(s) and scope(s) end up being completely surrounded by foam, but then that sheet of foam works only for that combination of guns and scopes. I didn’t particularly care for the latches because it looked like they could get snagged and opened fairly easily. I made two flights with it, and both times the latches were open when I claimed the case. The pad locks kept the case from opening all the way, but the seal around the lid was useless with it partially open.
Dumped it and went with a Boyt hard case that works on the same concept (cut out the shape of your guns in middle sheet of foam). The latches on the Boyt resist incidental opening. This one also requires that you supply the pad locks (non-TSA locks only for firearms). I’ve flown twice with this case, and it stayed tightly closed both times. A little trick is to position the rifles such that the serial numbers are exposed when the case is opened. When the SAPS goes to match up your serial numbers with your paperwork, you can point to the numbers without digging the rifles out of the center sheet of foam. These cases are a bit heavy, so with two relatively heavy safari rifles, you’ll be pushing the 50 lb mark and other items will need to be carried in another bag.
I’ve now switched to the Tuffpak. Many places you fly to require a soft case once you get there. With this one you can shove two rifles, in their soft cases, into the case. You can also shove shooting sticks, socks, underwear, …. Once you arrive, your soft cases are there are ready, not taking up space in another bag. As mentioned by James above, if you go this route, get the non-TSA locking model.
Going with a duffel bag is a good idea. Until you actually weight a typical suitcase, you don’t realize how much of your weight limit is gone before the first sock gets packed. I use an Eagle Creek duffel (XL, 3 lbs), and it’s been to Singapore, Indonesia and the RSA and is still going strong. When we got back from the RSA, I went to grab it and realized it wasn’t mine. 2 more went by before mine came out. 4 identical bags on one flight. Anyhow, there are bunches of good duffels out there.
As someone already pointed out, a good airline case for 2 rifles will probably set you back more than $150. Watch them bounce your case off the tarmac one time and you’ll be wishing you had a good case.