BSA airaporter/ mercury o ring/ piston set up.

[Dornfelderliebe]

Your next problem with the Airsporter may be that of running out of leverage. The underlever will hit the trigger guard before the sears lock up

Just another challenge to overcome. To be continued.

[gunshop]

The spring is a chambers standard. As is the buffer washer. The o ring in one I ordered from the internet. I ordered the standard airporter size and the mercury size which is one smaller. I forget the sizes just now but one was 11 and the other 10

The Airsporter and Mercury O-Rings are the same size, they are the same pistons and cylinders.

[Dornfelderliebe]

Your next problem with the Airsporter may be that of running out of leverage. The underlever will hit the trigger guard before the sears lock up

Taking careful note of your point James I used a spacer and there is now 1mm between cocking link and piston, rested and it cocks before the end of travel.
I expected an increase in power but it is sitting stubbornly at 640 fs with superdomes.
What did change is the cocking effort, from feeling like it was going to seize it is now very easy to cock, a pleasure in fact.

I did notice one thing this time. Pushing the original piston in, it moved (all be it stiffly) along the first section of the cylinder and became almost impossible to move at the compression end.