Firstly, tell them it's 'sporting goods' you do not have to state it's an airsoft weapon, the Royal Mail can't refuse it unless it's on their 'restricted list' but they are about THE most expensive to send anything these days
I only get asked if it's flammable/won't explode/etc. when I have sent stuff through the post office - even after saying it's an airsoft gun. Maybe the clerk on the desk was just in a pissy mood that day.
Except lead pellets and other airgun and airsoft projectiles.
Batteries
Batteries that are classed as dangerous goods by the latest edition of the International Civil Aviation Organization’s (ICAO) Technical Instructions are prohibited. This includes wet spillable lead acid/lead alkaline batteries (such as car batteries), used alkaline metal, nickel metal hydride (NiMH), nickel cadmium (NiCd), zinc-air batteries, and damaged batteries of any type.
Lithium ion/polymer/metal/alloy batteries when not sent with, or contained in/connected to an electronic device, are prohibited.
Lithium ion/polymer/metal/alloy batteries are allowed when sent with or contained in/connected to an electronic device, but are subject to packaging, volume and quantity restrictions. Please seewww.royalmail.com/restrictedgoods.
Sealed lead acid batteries are allowed in the UK, but are also subject to packaging, volume, quantity and labelling restrictions. Please seewww.royalmail.com/restrictedgoods
Alkaline metal, nickel metal hydride (NiMH) and nickel cadmium (NiCd) batteries may only be sent when new and in their original packaging. Please see www.royalmail.com/restrictedgoods
Weapons
Including Section 5 firearms (e.g. handguns, machine guns), CS gas and pepper sprays, flick knives, tasers and stun guns. Items that appear to be prohibited weapons may be subject to additional checks and delays.
Guns for sporting use, including Section 1 (e.g. hunting rifles), Section 2 (e.g. shotguns) firearms and low-powered air weapons may be sent in compliance with UK law and subject to domestic controls on the possession of firearms. Please seewww.royalmail.com/restrictedgoods
Guns intended for sporting purposes - including Section 1 (e.g. hunting rifles) and Section 2 (e.g. shotguns) firearms, low-powered air weapons and their component parts - may be sent in compliance with UK law and subject to domestic controls on the possession of firearms. Antiques, deactivated and imitation firearms are also permitted. When sending deactivated firearms include proof of deactivation.
Items that appear to be prohibited weapons may be subject to additional checks and delays. Please seewww.royalmail.com/prohibitedgoods
Use 1st Class as the minimum service. The sender’s name and address must be clearly visible on the outer packaging.
As Spatch says, don't make trouble for yourself by telling a clerk who may well not know wtf they are talking about anything they can get their knickers in a twist about. Just say "Sports Equipment".