Quote Originally Posted by Benelli B76 View Post
I service 5 or 6 rifles a week and never had this problem before with the 100 which I find is one of the simplest rifles to work on. What you say makes sense. Fortunately I have a huge collection of O rings in various materials. The polyurethane one that worked was a tight fit on the valve and of a very high Shore hardness, almost like nylon, and sealed well.

Baz
Yes it is rare that you just cant get one to seal, I have only seen two and only one had to change the valve, and like you I service these regularly.

What's bizarre is the o-ring works by deflecting under pressure and basically jamming itself into the gap causing a seal, so a softer one should work better as it's not a gasket, but sometimes the poly ones do work where rubber fails, I can only conclude it's a tolerance thing?