*sigh*

I still can't get it to work. I checked out your file and I see that inside there aren't any extra faces, but I can't do it. This is what I am doing:

("IMAGE #" refers to screenshot attached)

1. Position perspective view in the barrel and move towards the problem area.
2. Select the two faces that are in place at the opening. (IMAGE 1)
3. Click on Edit Polygons -> Delete Edge.
4. Move the camera outside the gun (IMAGE 2).

As you can see, the structure of that portion of the gun is gone! I don't understand how else I could delete them. I realize I could just use the file you attached, but that would just wind me up here the next time I have a similar problem.

Thank you!