Could this be the ultimate piston seal?
Been looking for an alternative seal now for a while, something off the shelf, easy to find and that works as well as an O ring if possible with minimal lost volume. Scouring the Hydraulic seal suppliers I came across Kastas.
Click the pic for a link to the site, I highlighted the seal I will be testing next on 25mm pistons.
The reason for this seal was its size, it is around the same size as an O ring but is made of polyurethane, the pressure groove is tiny so the lost volume should be minimal and the seal sits in an easy to machine flat bottomed groove. My plan is to test the seal with flat fronted pistons (bronze piston nose) running tight tolerances to minimise the lost volume even further.
Some addition pics of the seal.
Will update with some results and installation pics as the seal, as you can see its pretty small.