Is that a sump pump hole in the floor of the gun room? If so, I'd be nervous about excess humidity, though it looks like you also have a dehumidifier there.
You might attempt to minimize evaporation of water from the sump by putting a loose cover over the hole. It might minimize evaporation while allowing the sump to "breathe" when the pump operates.
If I can't be with the rifle I love, I love the rifle I'm with!!