I think the standard these days is 3" chambering with many shotguns chambered for 3 1/2".
I inherited an Ithaca 37 when my dad died 2 years ago. I'm thinking of selling it as I already have two shotguns I don't use, don't need a 3rd. But I'm wondering if a potential buyer would be put off by the fact that it can't handle anything more than 2 3/4".