Here's some advice I posted on an earlier thread on the subject:
Hi guys,
Looks as there is a lot of confusion and misunderstanding on the Carriage of firearms and ammunition on air transportation.
First is to understand there are three elements involved the Carrier, the Handler and the Airport Security.
The Carrier is the airline that you are travelling with and they should be the only aspect you need to deal with prior to your planned flight. Under ICAO rules they (the carrier) can carry up to 5 kg of (Sporting) Small Arms Ammunition of HD 1.4 per passenger. “Sporting” is used to distinguish between commercial/ governmental/ military transportation. The reason it is preferred to be in the manufacturers’ packaging is that it has tested and given a UN certification and where necessary a ESTC transportation code. Although carriers have this dispensation to the carriage of dangerous good by air, they are not obliged to so, and have the right to refuse. The carrier may request proof of permission to hold as arriving in a foreign country without a legal reason to have said firearms and ammunition can lead to a prosecution of the carrier. Same as arriving without a valid passport or visa.
The Handler are the ground crews who look after the aircraft, load it up, refuel etc. All firearms and ammunition should be treated as “secure baggage” that means it is taken from the check in area directly to the aircraft by the handler or their agent and not along the baggage transportation system. The Handlers may charge the Carrier to do this and as a result the cost may get passed onto the passenger.
Airport Security are responsible for ensuring prohibited and forbidden items are identified in baggage and on passengers. First thing to remember is that prohibited does not mean that it is not allowed, just that its carriage requires additional conditions. You should not go airport security before reaching the check in so generally it is not an issue. In high security airports then just declare that you are legally carrying firearms and ammunition and have your legal paperwork ready. You can also ask for items found at security to go into secure baggage as well. For example I was carrying a laser sight in by hand baggage (many years before the high intensity lasers came out). The security declared it as an offensive weapon and said that it would be confiscated. They were very surprised when I said that although they had the right to declare it an offensive weapon they had no right to confiscate it and I wanted it to be sent to the cabin crew as secure baggage. One of the security staff had to then come to the gate and hand it over to the cabin crew and it was given back to me as I got off the flight. The same as injected medication etc. It can be handy when you know the rules better than the staff!
So, contact the carrier and only the carrier and ask do they allow the carriage of sporting firearms (never use the term weapons) and ammunition and what are THEIR requirements. Declare at the time of booking the flight (phone up after booking online) and again at arrival at check in.
Having said all that, I’ve stood at baggage claim desk while they were frantically trying to find my ammo when the wife spotted it coming down the baggage carousel with everyone else’s bags.