What ever kind of shotgun you decide on, be sure you have it in a case
of some kind to keep mice or mud dobbers out of the barrel.
The thing would go off like a bomb, with an obstruction in the barrel.
I also like the pump,ours is a 870 Rem 20 ga.
This is one of the reasons I like a single, or if the price was right an old side by each double. When you pop 'er open to slide a couple shells in, a quick glance down the barrel(s) tells you immediately if the bores are clear (or not!)
Easy to clean, reliable as a hammer. This going to be a neglected gun, barn guns always are by accident or design. By neglect I mean it's going to be a grab and shoot tool, not one that gets regular cleaning and attention. That's no reflection of the owner, it's just the way it happens in 99% of cases.
Nothing like a load of light buckshot for varmints, .25 to .30 cal really does a job. 12 bore would be my choice too, unless the lady of the house insists on a 20.. in which case she needs to pull on her "big girl" drawers and live with a bit more recoil to get the job done. My wife suggested we use a .22 on coyotes a few years back. I just looked at her and said, "Sure, it'll kill 'em, over the next few weeks maybe".
She soon got used to using my .270, much more suitable weapon without going out and buying a coyote specific rifle. We have a lot of restrictions as to .222, 22-250, etc here, which is a real shame as I'd dearly love to have a varmint rifle. I won't spend that kind of cash just to shoot an occasional coyote, though. The .270 is overkill, no question, but it definitely has the authority to get the job done humanely.
Sean