These items must be sent via the Post Office only, and "presented at the counter".

[Sacarathe]

http://www.parcelforce.com/help-and-advice/sending/prohibitions-and-restrictions

 

Quote

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:

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

 

Presumable this means "acknowledged or announced"?

[lemon191]

Yeah , they won't want you whipping out guns in any form in a post office 

[TheFull9]

Actual Royal Mail has different rules to Parcel Force, you want to use RM most of the time.  PF won't cover more than something like £50 insurance wise if they lose a £300 RIF.