The couple double bead guns I've had have been pretty close, with the exception of one. I had a Mossberg 500 with rib/double bead that had a POI 3-4 inches left and 2-3 inches low. The add on fiber optic sights almost fixed this problem, still had to float the fiber optic sights a bit right to get the pattern centered. Missed a big gobbler close because of that.
The above is a good example of why people need to pattern their guns, and not just assume.