Hi everyone, I've had a HW100 for 4 years now & it's developed an air leak.
When I attach the air cylinder, air begins immediately venting from a small hole on the underside of the valve housing at quite a rate. I have changed the 2.57mm x 1.78mm O ring on inlet valve stem but this has had no effect? The cylinder hasn't been removed from the rifle very often & hasn't suffered any damage. Any thoughts on the cause?

KR Andy