[Vanya117]

I've had this leak since last summer. A small hiss coming from what I can tell is around the breech. If I stick my finger in front of the bolt I can feel the pressure and hear it.. I'm about to order a new donut, but don't want to order it, just for it to still leak. Is there a way I can test my gun to see if thats it? I read someone say of you mess with the hpr itll change tone if its your donut. Tried it and it never changed tone. Same with the LPR. I want a fail proof way of diagnosing what it is before I order a part for nothing.

[martix_agent]

try replacing the big orings around the engine first, or the small orings on the outside of the engine.