I'll get back into it in the morning, Jon, I had to abandon it this afternoon as a rush job came in.
I still have a few tidy up jobs to do on the gun, I designed the piston to have 2mm clearance with the cocking arm, the Knibbs seal I used turned out to be 1mm shorter than a Weihrauch seal so cutting the clearance down to 1mm --- a quick file of the cocking arm will sort that, or I'll just get a new genuine seal.
The barrel looks like it could do with checking for straight and given a quick tweak, it's also crying out for a barrel weight come cocking aid, so while I have the .22" barrel off I may as well fit my spare .177" K barrel and run a chrono string with that.
So far so good though.