Whilst waiting for some scales to come from Abey I decided to strip down my Kral Devil which has been steadily and gradually losing power since I bought it,two Black Fridays ago.
Down from 560fps to 520 the other day with 14.5 gr superdomes.

I expected to find a damaged seal but I can see no damage to it. Nor is there any serious scoring to the cylinder. Some machining marks seem to have polished and the rear bearing section of the piston is pristine.

The only things I can think have gone wrong is the spring has shortened or the breech seal has worn ( no visible knicks).
This weekend I going to polish & deburr it.

Any suggestions chaps?