https://www.parcelforce.com/help-and...d-restrictions

The bit you need is:


Arms and Ammunition - low powered air weapons Low-powered air weapons (air rifles, air guns and air pistols), together with lead pellets and other airgun and airsoft projectiles, can be sent but are subject to the following conditions:

These items must be sent on an express48 service only
These items must be sent via the Post Office only, and presented at the counter
Enhanced compensation cover is not available

Enhanced compensation cover is not available, means you are capped at £100 insurance if it gets lost or damaged. That's the main risk involved