Try raising your head a little higher from where you normally rest it.You will be seeing more of the vent rib when you do this. Now sight the same and your shot pattern should come up.

This will happen because as you lift up your head while sighting down the gun barrel, the bead will appear to be going lower. Thus you will pull the gun up to compensate, and your pattern will come up. With a little bit of trial and error to find out where you need to rest your head, you should be able to get teh pattern right on.