I hunt almost exclusively with smoothbore shotguns nowadays. My sights are a Hiviz green front sight and a glob of white-out at the base of the vent rib as a rear sight. I can easily keep rifled slugs on a 9" paper plate at 100 yards all day shooting off my knee, and there is nowhere in the eastern forests where visibility is longer than that.
The first deer I shot, however, was with a .270 outfitted with a 2-9 power scope, set on 4, I believe. The shot was taken at 40 yards, and I found that follow-up shots were challenging, as it was difficult to visually acquire a moving target with a scoped weapon, even set on a modest 4 power.
On a side note, that deer was struck perfectly through the lungs, and the bullet was found to have mushroomed as designed. The deer (a 220 lb. buck) nonetheless managed to run over 100 yards, and took me an hour of tracking in the dark to find.
That experience left me prejudiced towards scopes, as well as small-diameter projectiles.