Ok so after putting the gun back together and replacing the piston washer with one from John Knibbs. The gun no longer shoots.

It cocks fine but when I pull the trigger it makes a "phutt" sound and I can see the piston just move slowly up the cylinder.

My guess is that the piston seal is wrong and is letting air past.

Thats not all, the trigger adjust and lock screw I ordered from Knibbs are longer than the original and so wont screw in correctly, I can file these down but still, kind of annoying.

So on that note, where can i get a proper leather piston seal for a BSA Club Special? (I believe its the same as the standards)

Cheers