Two thoughts here. First, if it is legal to carry a semi-auto with you when checking the trap line, you might want to consider going that route. While working up some test loads for my contender, I took my sons Ruger single six to shoot while allowing the contender barrel to cool. When I got home I decided the least I could do was to clean the Ruger, since I got it dirty. What a pain in the butt scrubbing all those tiny holes in the cylinder. If you have a semi auto you just clean the bore and your done.
If you are not allowed to use a semi-auto, then I would recommend the Ruger single six. The interchangable cylinder also allows you to use .22 mags, not sure if they would be an advantage on the trap line or not. The Ruger is available in stainless, and all of the single sixes I have ever shot were very accurate.