That’s a choke, for adjusting the pattern of the shot. For home defense, remove that choke - you want as wide as possible. Chokes will tighten the spread.
bump
For home defense, remove that choke - you want as wide as possible.
Don’t fire the gun with the choke removed, it will damage the barrel threads, just buy a cylinder choke or skeet.
You don’t want to remove the choke tube, that will ruin it.
You should replace it with a IC or cyl tube if you want more spread in the shot pattern.
Most hunting shotguns will come with a mod tube if only one comes with the gun.