Depending on load, etc, most shotguns with beads mounted directly on the bbl shoot higher than POA, some as much as a foot high. Impossible to tell in advance.
The sight pic I use is no rib or bbl, just the bead seeming to sit right on the flat grooves on the receiver.
I was going to the rnage yesterday to check zero on my M/L for the deer season.I had chucked a few packs of KOS and Winchesters in my duffle and packed Frank for a test of just this, but I got paged for work. Will try this weekend and will post results.
HTH....