Unless the regulations have changed it states that all ammo must be packed seperatly from the firearm (in your main baggage) and unless over 5kilo in weight it is perfectly ok in makers boxes. It is is over 5kilo it has to be in a locked metal box.
I have flown with Firearms many times, and you will find that very few working at the airport know the proper procedures
1. You should inform the airline you are travelling with that you are carrying sporting rifle and ammo. Make sure the airline carries firearms, Ryan Air has stopped, so to AA.
2. Make sure the gun is in a locked hardcase bolt removed, and that you have your British FA Permit, and your European Firearms Permit if you are hunting in Europe.
3. Make sure you allow at least 3 hours check in. On arrival Airport security should take you to customs, where the gun case is Xrayed, then onto a private customs room, where the case will be unlocked and they will check the rifle details against your FA cert. All well the security guy takes your FA and puts it on the flight.
4. Coming back into the UK, you will need to go to oversize baggage, security should meet you there and take you to customs to check the same guns are coming back in.
Thats briefly what should happen, but airlines and the people that work for them, well lets just say they are not all conversant with the handling of Sporting weapons.
Good Luck.