Good information and advice provided so far, but I think your buddy needs to start with knowing where the gun shoots (POA/POI) as a starting point. If the shotgun is not centering the pattern when shooting with the existing bead sights, then the first question becomes whether or not he will be comfortable shooting a red-dot or holographic-type sight (some people are not),...or if something needs to be done to the bead sights to get the pattern centered.
Regardless, the first step in the process is confirming that the gun shoots where it is being aimed. I say this because I have seen too many people grab their upland game/waterfowl shotguns to go turkey hunting that have never shot those guns in the "still target" format of shooting at a fixed target at various ranges. When they get on the shooting range to do that, too many have found out that their gun's patterns are not centered in relation to where/how they are aiming the gun.
When shooting at turkey-head-size targets,...and with any sort of suitable choke/load needed for turkey hunting,...any off-center pattern the gun might have is only going to be exaggerated. Bottom line for me is to make sure the gun shoots where it is being aimed by the guy that will be hunting with it first.
