I just found this site and this will be my first post. What a great opportunity to communicate thoughts about a common passion. Talking about hunting isn't as good "doing it", but it's close.
Robert has been given some good advice in this thread, but I think it's not addressing the problem. I suspect Robert's problem is an improper gun mount. If switching from one gun to another makes a noticed difference in performance, it's almost always in the way the gun fits and comes to the shoulder. If the gun isn't mounted correctly, it doesn't matter what else is done. How the gun swings, balances, and patterns doesn't matter. If you ain't pointing where you are looking, count on an empty bag at the end of the hunt.
The most productive time we can spend improving out shooting is standing in front of a mirror and practicing our mount. Bring your gun to shoulder (it's usually best to unload it!
). If it isn't pointing straight back at you, you need to correct. Practice, until it's automatic. Remember, Ol' Betsy is going to mount differently after you pile into all of your cold weather gear. A shortened stock is an excellent investment for cold weather outings. My duck guns are all a bit shorter than my dove pieces.
To open a can of worms for thought and discussion: It's my opinion that a pattern board tells us little. It applies a two demension answer to a three demension question. Remember that a shot string is just that, a string. All of your shot doesn't arrive at the same time. It all piles up at the same spot on the board, but it doesn't look like that in the air. To get a true picture of what your loads are doing, you have to pattern on a moving board. Bob Brister did a good deal of testing on this some years back, with some interesting results. You may have a bunch of shot in your circle on a fixed board, but large holes where your target and shot string cross.
Also remember, because the shot is in a string, it's harder to over-lead a bird than to under-lead. He may fly into the tail end of your string, if you over-lead. On an under-lead the whole string is going to miss.
The above is opinion, only. Your mileage may vary and I welcome any comments pro, or con. Wishing you locked wings over your rig.