Originally Posted by
RossB
On my BSF S70 the leather piston seal is retained with a screw.
The seal itself is a four piece setup.
A hard red fibre disc behind the seal, the leather cup, with a leather centre washer topped with a red fibre centre washer.
The slotted flathead retaining screw appears to be M4 x O.70 x 15 mm.
No, I did not just take the gun apart - I have 2 spare seal sets and screws.