At Gatwick the luggage handlers tend to lurk around the carousel in the oversize luggage department and then hand them to you on provision of paperwork. Don’t think I’ve ever gone through red channel but thinking of it, I’ve only flown from Scotland so assume there isn’t customs.
Possibly, we were coming back from the States and this was at Heathrow.
On the upside, on the way through Heathrow going out, Group 4 take everything you have as soon as you get through the doors, and it's VIP treatment until you get through to air-side.
No waiting in the queues with the rest of the travellers, they take everything from you, scan all the luggage and do the processing to one side - you're through the check-in process in minutes.
Coming the other way is even easier, TSA just want to check your paperwork and the airline do all the work. Just watch combined ammo limits (the whole plane will only take a few kg total) and now every bag checked with ammo or firearms is charged a fee, it was $60 when we came through but that was about 10 years ago.
But seeing as the process to just travel to Europe through Stansted in the last 12 months has changed almost monthly, I guess international with firearms may have changed as well.
ETA: BA now charge £125 per bag with restricted items, and the baggage counts towards your 'free' baggage allowance. But it goes in Hold5, which is the hold for all the restricted items, late items or items removed from the cabin, so it gets special treatment for the £125 fee.
