I have just modded my HW 35 E to accept a Venom plastic (green colour) washer.

When I got the rifle it still had the leather washer fitted but was also deiselling heavily.
I modified the front of the piston on a lathe to accept the Venom washer, and managed to gain a little more swept volume in the process.

I seem to remember being advised years ago not to use silicon oil on this type of washer, although a "smidgin" of moly grease would be OK.

I have assembled the rifle (taking care) and used a smidgin (tiny smear) of moly on the outside of the washer, and the rifle is still deiseling

I took care to clean the inside of the cylinder with meths when I stripped the gun, which was left overnight to dry off.

What material is the Venom washer made from? and why can't you use silicon oil (a drop smeared around the outside) as I do with other plastic type washers ? Any advice would be appreciated.

Paul