On the B@y shall it be known as 'Long Part', 'Projectile Farewell Tube', 'Arc-forming Tube-Lever', 'Spare 22 Part'...
dual-purpose cocking lever
Probs a bit more for an original barrel.
Vintage Airguns Gallery
..Above link posted with permission from Gareth W-B In British slang an anorak is a person who has a very strong interest in niche subjects.