Typical warning: I'm not a lawyer and this isn't legal advice.
We don't have any law regarding loaded guns. We don't have a law against concealed long guns in a vehicle. We do have a law against concealed handguns in vehicles and on person. You could open carry it, but IMO that's asking for more scrutiny. Also open carry is prohibited without a CHL in, as far as I know, Portland and beaverton (or is it tigard).