If that food storage bag is easy to rip open, then yes.
I'd go for something in stainless, with a synthetic stock. Barns aren't particularly weathertight.
I would go with all thats has been suggested all good recommendations
if you decide on the H&R top breaker the newer version is called the TOPPER, cheap but effecient they even make tacticool stocks and what not
when i was younger dad had one take down and buried in the trunk when we did long distant travel
handy little guns
like shown get a gun sock and long plastic bags with desicants it will last forever or inside PVC as already recommended, seal the shells in thick food storage bags with desicant also
you can pick up the marine version of the Hatsan escort for about $200 new. I got my parked version for $165. It has been reliable.
Saw some pumps made for boat use that are chrome coated, cannot remember who makes them, Winchester?
IIRC, both Winchester and Mossberg made "Mariner" versions with either nickel or chrome plating from the factory. Used to have one of the Mossberg 500s, good gun. Pretty expensive to leave unsecured in a barn, though.
As an old geezer, when I lived on a farm in my youth my dad used to keep a old double barreled 12 ga shot gun out in the barn for fox's raccoons & varmints. It was a Damascus double hammer that you did not hold on to the for arm, other wise when shot the gun would take it self apart. I used it on squirrels until I as 16. It was left in the rafters above the cow stalls and only got wiped down with an oily rag occasionally, But in those days nobody locked doors or cars for security. I got over my fear of heights after using it on some pigeons shooting a hole in the barn roof that dad made me fix, :nono:as I recall it was at lest four stories up in the air next to a down spout.:scared:
PS-With the craziness that is ensuing the gun market right know, these guns will more likely be in the $200-$250 range.