Quote Originally Posted by BTDT View Post
It would be a start if someone could tell us how the BSF piston washer is fitted! I can't remember for the life of me, but then I have probably not had a BSF apart since the late 1970s.

If the seal is held by a screw then it should be easy to get a PTFE head turned and attach it in the same way. If the seal is held by a rivet like the Original 45, I'd turn the rivet section off and drill/tap a central hole (actually, I'd have to get someone to do it for me because I don't have access to a lathe nowadays ).

I'm not at all convinced by the notion of turning the head of the piston down to enable a clip-on seal to be fitted.
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.