I stripped, degreased and relubed a BSA Meteor according to Hsing's tuning guide posted elsewhere on the site. New piston spring, seals, breech seals etc.

Put the rifle back together and when cocked, there is a clack clacking sound (not dissimilar to the sound of an anti beartrap on some rifles.

At first I thought I'd bodged putting the trigger back together and this was catching, but checked it and it's fine. Then I noticed shallow parallel scratches along the length of the spring and it turns out that the 'teeth' on the cocking slide that slots into the cocking slot is catching on each coil of the spring as I cock it.

The spring seems the same diameter as the original and is supposedly the 'factory' spring for it.

Anyone have any ideas? As it is starting to pee me off.

(On the plus side, the tune worked as it shoots beautifully).