is there a pump slug gun that will shoot 3 or so into sub 2 inches at 100 yards? Just curious.
Is there one? Sure. They'd be pretty rare though.
But this is the internet and i am sure there are plenty guys who'll speak of or show the one best "2 shots touching and I pulled the 3rd" group of all time at 75 yards and post it as an "all day long" 100 yard group.
The savage 210/220 and H&R single shots are a different story though. Very consistant.
Unless considering the above named shotguns or a semi custom (tarhunt), on the averages, a typical ML will be more consistently accurate than a typical shotgun.
ALso consider ammo. Shotguns can be picky in the slugs they prefer. Some shotgun slug ammo is ridiculously priced. YOu could spend a few hundred bucks testing brands and practicing at long range. With a ML you can load develop at the bench and save money via economy of scale. Something to consider.
Obviously either way , SG or ML will work.
That savage 220 is really at a whole other level than an 870, rifled barrel, & scope. If you are leaning SG, I'd strongly consider it.