You shouldn't see any of the barrel, just the top of the reciever and the bead.) You probably also have the bead out of center to the left, causing it to shoot left.
I will be sure to account for this next time I practice "hold/mount."
Of course, I still believe that Im also anticipating recoil and thus, demonsrating sloppy, last second form. Once I "slow things down" and pay attention to what Im doing, my shots move much, much closer to center/POA...if not dead-on. Essentially, I am still making too many assumptions regarding the shotgun and simply not taking the necessary time to "aim" properly.
As a side note: Im using a Meprolight tritium front bead only and, given the heavy walled barrel Im currently using on my 590, it seems to have naturally set in at just about dead center. Now, with the original heat shield barrel (thin walled), the Meprolight sight seemed to require a bit more "positioning" in terms of yaw.
Its always amazed me how even the slightest variance in hold, trigger technique, form, etc., is capable of throwing shots off by such a large margin, even when concerning shotguns (handguns, of course, being far less forgiving). It just goes to show that shotguns do indeed require "aiming" just like any other weapon. Now, I knew this beforehand, but the more I fire shotguns (and handguns for that matter) the more prevalent this fact becomes. Hence, I wonder about these individuals who go out, buy a weapon for HD use and then never bother practicing and yet, insist that they are prepared for any type of violent encounter. Oh well, that is for another discussion.