May I suggest you discipline your mind to stop LOOKING at the ENTIRE Bayonet lug, and instead, imagine a line down the middle of that lug, and let that line be your front sight. That should reduce the windage( width) of your groups substantially.
If you take some White out, or " Liquid paper', and put a white dot, or line on the back of the barrel, your eye will use that as a centering reference. If that works for you, you can invest in a small bottle of white enamel paint at a hobby store, and replace the white-out, with the painted, line or dot instead.
The only thing left for you to learn to do is to mount the stock to the same place on your jaw/face each time. Some shooter put a tack in the comb of the stock, as a reference mark for this purpose. Considering how sensitive the skin of the cheek is on most everyone, I think a piece of tape, or anything that is dissimilar to the finish of the wood stock will be "Felt" by your cheek and let you know if you have mounted the stock to your face consistently.
Mounting the stock takes practice to do it right. My problems shooting a shotgun accurately were only solved when my late friend, Jim Gabbard, had me practice pushing the gun out away from my shoulder, and then bringing the stock back so that my eye was looking down the barrel at the front sight, before the stock touched the pocket of my shoulder.( elbow out Straight from your shoulder to create the pocket. Leave the elbow "up" while you shoot the gun. It keeps you from canting the barrel, and helps you shoot with your head Up and on the Side of the stock, not the top of it, where recoil is going to smack your cheek, and bump your glasses so that the nosepiece bruises your nose. Lousy way to develop a flinch. I speak from personal experience. :shocked2: )
I know this sounds a bit much, but I saw my personal performance with my shotgun streaked upward after doing this exercise at home 50 times a day for a month, facing a mirror with an aiming point marked on it. I went from breaking 16-19 clays at 16 yd trap, to breaking 23-25 targets per round( 25) in a few short months. As I gained confidence, those scores went up to 24-25, and I began shooting the handicap events, to increase my yardage to challenge my skills further.
So. take the time to set that gun up right so you can control the sight picture. I know at least one member here reports filing a small narrow "sight" out of the top of the bayonet lug on his gun, so that he had a narrower sight to look at when shooting the gun. The Bayonet still fit fine over the lug, and locked securely to the barrel with the socket. That worked for him. Be inventive. Its your gun. :hatsoff: