Old bloke was 100% spot on in his diagnosis,took the button out and cleaned throughly with surgical spirit(both limbs) and the spring and the screw.
By the way put the limb in a plastic carrier bag when unscrewing and that way you dont lose the little spring that comes out the speed of an exocet missile.
Anyhow 200 shots later and not one low arrow i have to say i am delighted with the result and wouldnt have thought to look there in a million years.
Believe me i was amazed at how much dirt was in there and equally amazed at how the limb now just slips so easy into the pocket with a nice click.
I for one will be making this a regular part of my maintainance routine as i was gobsmacked that a bit of dirt could have such a dramatic effect,and believe when i say it was dramatic.
Thanks a billion old bloke and i will be in touch about the chocolate
