The size restrictions on luggage with most airlines usually does not apply to gun cases. You will need to check with each airline separately to see what their specific restrictions are regarding gun transportation and baggage rules.
Delta has a 2 gun limit (without excess fees) and has not enforced any type of a size limit on the case as it falls under their exceptions for baggage. I have been told this by Delta directly and have never heard of any hunter being charged extra for his gun case as long as he has 2 rifles or less. They do allow for more than 2 guns, but may run into excess baggage fees.
I travel extensively throughout the world all year round to hunt. Usually doing at least 2 around the world flights each year hunting internationally.
Going in and out of different countries with many different airlines can be stressful at times. Let me try to give you some points about traveling with guns and airlines.
One thing that is very important to check before you fly is if the airline is going to require you to have your gun permit IN POSSESSION with you when you fly. That can be a real problem and has caused some hunters a lot of headache at the check-in when they don't have their gun permit with them. The problem is, that many countries / outfitters will have your gun permit issued when you arrive. The airlines have on their computers the restrictions for each country on guns, but sometimes it is not up to date.
Best to get your travel agent to make sure that there is a note in your reservation that you are traveling with a gun. This has saved me on a few occasions when I insisted to the check-in agent that I had "prior approval" and it is noted in my reservation that I am traveling with a gun.
Also important that you have your entire itinerary checked for gun compliance. 2 years ago I flew British Airways from Seattle to London to Cape Town to Johannesburg. Lots of changes and checked luggage all the way through. Since I was only transit in England, I did not have to claim the gun at luggage and re-check. They put it through directly (not sure they will do that anymore - need to always check for new regulations before you go). The problem I had was when I arrived in Cape Town (1st city of entry into your destination country you have to comply with customs and get your gun permit. The gun permit was easy in Cape Town as their are very few hunters and no waiting (not like Johannesburg where you can wait for hours in a line to get your gun permit with so many hunters there). The police agent in Cape Town was actually looking for something to do, so he told me he would fill out all the paperwork and that I should just go and have a coffee and come back in 15 or 20 minutes and it would be ready for me. Wow! What service...I was impressed and thanked him very much for his assistance!
The problem then came to recheck the bags. The airline partner that British Airways used for their route from Cape Town to Johannesburg did not have licensing with South Africa to transport firearms! Luckily I had the bags checked all the way through to Johannesburg, so the local airline rebooked me (on their expense) on South African Airways so I could take my gun. It was good service, but still had to deal with that issue and caused a lot of stress until the airline management there said it was not my fault and that I did have the guns checked all the way through by a British Airways agent in Seattle -said it should have been caught in Seattle and not allowed me to board with my gun!!!!! So a word of warning....please check with all the airlines you have connections with through your entire trip.
I have had guns completely destroyed when using a regular hard sided gun case. Has happened to me a few years ago when flying back from a hunt in Russia. Was flying Moscow through London Heathrow and on to Seattle. When the bags arrived in Seattle, my gun case was half missing and twisted like a pretzel. The scope had been scraped half off and the barrel bent and twisted. British Airways would not take responsibility even after I filed claims and sent many letters. Best to stay away from British Airways when traveling for hunting. They are not very hunter friendly and until they change that attitude, the don't deserve the hunters dollars.
I now have been using a couple of different cases - a Tuffpak case and also an SKB Freedom case - both are look like golf club cases. I can put 3 guns in the case (with each being in their own soft case to use on the trucks during safari). Along with the guns, you can fit some hunting boots, rain gear and other items in the case also. Have to watch the weight limits. I usually only take 2guns along with some gear. (good place to put the camera tripod too). Using this set-up I normally have no problems as many do not even know it is guns that I am traveling with. I would rather be less conspicuous when traveling anyway.
Some airlines (not all) require you to remove the bolt from your rifle and have it separate.(South African Airlines requires this). Just remember to NEVER TAKE THE BOLT IN YOUR CARRY ON!!!!!
You will need to pack the bolt in your checked luggage.
Some airlines will require you to pack your ammunition WITH your gun together. Some airlines will require you to pack your ammunition SEPARATELY from your gun. YOU NEED TO CHECK WITH THE AIRLINE IN ADVANCE.
TSA regulations in the USA have changed on this topic over the years. For many years it was required to pack the ammunition separately from the guns and many ticket agents (and even some TSA agents) still think this is the rule. But actually the rule changed in 2002. Now you are allowed to pack your ammunition in the same case as your gun. (please check this before you go as these rules can change at any time). Packing the ammunition in the same case as the gun makes life easier, because ammunition must be locked and if you have it in a separate bag, that bag needs to be hard case and locked! - NOT A DUFFEL BAG! Some airlines won't catch this, but that is the rules for most.
The rules on ammunition are max 5 kilos (about 11 pounds) and must be in a hard case and locked. No loose ammo!!! Keep it in the manufacturers boxes and inside a hard locked case. And please always check your carry-on for ammo!!! If you are like me, I use a backpack for my carry-on so I can use it on the safari for a day pack. But as normally happens during the hunt, some ammo gets loose in the pack!! Please check your bags before going to the airport!! I have had this happen when I arrive in Beijing, China one time, and it really caused a stir when I went through the security scanner and there was loose ammo in the bag!!! That took a lot of explaining an could have resulted in some unwanted jail time in a Chinese prison!
Your gun case must be hard cased and locked. It is not supposed to be locked with a "TSA-friendly" lock either!! So take a different lock (key or combo). I use a combo lock as it is easy to lose keys on a long extended trip! -just a tip...
Some airlines have their own restrictions on ammunition limits also. Qantas airlines has their own limits and does not follow the 5 kilo rule exactly. I was flying from Australia to Johannesburg, South Africa continuing on a round the world hunt...and had an issue with Qantas. With Qantas, you need to have "PRIOR APPROVAL" on your reservation for the amount of ammunition you are traveling with. Their airline has rules on the "total" amount of ammo that can be on the airplane from all the passengers. So if there are several other hunters on board with prior approval ahead of you, you may have trouble getting on that flight. You will need to reserve space on the plane for the amount of ammo you are taking with you!!
I could go on and on...but this is already a book..
Take care, check out your airlines in advance and have a great time hunting!!!
It is also good for you to print out the airlines gun restrictions (can usually get it on their website) as well as TSA rules on transport of guns and ammunition. Then you can have it with you if you run into an airline ticket agent that is giving you trouble. (remember there are a lot of anti-hunting ticket agents!)
It really is not that hard to travel with guns, just need to know some basics...