it can go royal mail if it meets the size criteria
Guns for sporting use
International - Allowed in the mail, see restrictions and packaging guidelines below:
Guns intended for sporting purposes - including Section 1 and Section 2 firearms, low-powered air guns and their component parts - may be sent in compliance with UK law and subject to applicable export controls on the shipment of firearms.
Items that appear to be prohibited weapons may be subject to additional checks and delays.
Guns must not be loaded.
Air weapons with an integral gas cylinder that are de-pressurised can only be accepted. Air weapons with gas cylinders that are pressurised are prohibited
Air weapons with a pressurised removable gas cylinder which is still attached are prohibited
Sender's name and address must be visible on the parcel.
Must be packed in rigid outer packaging suitable for the gun size and weight, for example a fibreboard box, with sufficient inner packaging to prevent movement during transport.
UK - Allowed in the mail, see restrictions and packaging guidelines below:
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.
Use 1st Class as the minimum service.The senders name and address must be clear on the packaging. Low-powered air weapons which exceed the Royal Mail size restrictions are accepted by Parcelforce Worldwide, using express48 via the Post Office.
Guns must not be loaded.
Air weapons with an integral gas cylinder that are de-pressurised can only be accepted. Air weapons with gas cylinders that are pressurised are prohibited
Air weapons with a pressurised removable gas cylinder which is still attached are prohibited
Must be packed in rigid outer packaging suitable for the gun size and weight, for example a fibreboard box, with sufficient inner packaging to prevent movement during transport.
Size guide here https://personal.help.royalmail.com/...detail/a_id/89
Size and weight comparison guide
Want to tell the difference between small and large letters? Watch our video Opens in new window
Letter - Greetings cards, personal letters, postcards, bills
Large letter - A4 documents, certificates, magazines, CD or DVD in cased, some large greeting cards
Small parcel - Shoes, portable speakers, mobile phones
Medium parcel - Gifts, shoes, heavy or bulky items
You may get it sent as a small parcel .
Don't lie as to what is in the parcel . . Its not a sporting goods item or metal sculpture ,Its a low powered airgun for sporting use which is in their terms as allowed to be sent via them.