I average a 2 inch group (sometimes all three holes touching) from my 870 12. gauge with a 20 inch barrel and srew in rifled choke. (Its got rifle sights). I shoot 2 3/4 1 oz slugs at max by winchester. (btw the SAME LOAD in Federal shoots A FULL FOOT Higher at 50 yards than the winchester). This is my "back-up" gun for elk.. since my scoped rifle doesn't have sights.
Accrracy is consistant and it sure gets a LOT of funny looks at the rifle range here in Colorado. (nobody hunts with slugs here)
I haven't TRIED shooting it at 100 yards, but I'd guess a 4 to 6 inch drop at 100. the problem is holding still on target with a hard recoiling shotgun trying to kick you into next year. I can only shoot about 6 rounds before my shoulder cries "no mas".
But if ya can't bag your deer with the first two... well maybe ya need to practice more.