It would really help me if the image was bigger - I can't read the text around it.
From what you've said, your problem could stem from the grommet not being tight enough around the pin. You probably need to make the counterbore where the grommet goes slightly smaller, which means that you'll most likely have to re-make the entire thing. A lathe would be quite helpful.
I guess that as long as you can see the picture, I can fill you in on the problem area (the rest doesn't matter.) Basically the main valve ID is 7/16in then it tapers to 1/4in and then it expands to 1/2in to fit in the grommet. It has friction between the firing pin and the grommet already, and the surface area of the ID of the grommet is about an 1/8in deep. I don't have access to a lathe, and I don't really want to have to spend alot of money to get it custom made. I know you do custom work for a relatively cheap price, but it's still an expense I'd like to avoid.
I'm having trouble with the grommet's seal on the valve I'm making. I epoxied it into place and the seal will hold up to 20 psi. After that, it leaks from the area between the standoff and the ID of the grommet. How can I fix this? I'm out of delrin so I hope to fix this without having to remachine the whole thing. Perhaps the trouble is because I made this on a drill press instead of a lathe, possibly causing a slight misalignment.