I'd pattern the turkey barrel adjust your red dot as necessary, when you are satisfied with that I would change barrells and pattern a couple of waterfowl loads at your hunting distance you use. Then compare the results, it should be self explanatory. I personally would think you would be pretty close but the patterns will tell you the story. Good Luck
Almost forgot i'll save you some money and pain sighting in your turkey gun.
Set you a target out at 12 yards with a 1" square in the center of it. Use light 2 3/4 inch shells. Shoot and adjust your red dot until you can shoot out the 1" square. Use as many targets as necessary. Then set a 36" x 36" target at 40 yards with a 1" square in the center of it. Now use your turkey loads. Use as many targets as necessary, use a fresh target with each turkey load shot. Once you determine where the dense part of the pattern is adjust your red dot to center it over the 1" square, then shoot another turkey load to verify the adjustment. It would really help if you had a rifle rest to do all the shooting, including with the 2 3/4 loads.
Forgot something else that is important, Clean your shotgun barrel every 3 shots, use your bore cleaner, Then use a brass brush about 5 to 10 strokes, and dry patch it, use your lube, and dry patch it. It will be like you just took it out of the safe. If you didn't your barrel would build up with fouling and plastic which would effect your patterns and shooting.
You didn't say what kind of turkey shell you use, if you have any problem with your pattern at 40 yards try a .665 Choke (I like a briley straight rifled choke) and Winchester Longbeard XR #5 shot.
One other thing you can do with your turkey gun and red dot sight, put a modified choke in the turkey barrel and use 2 3/4" shells, you can hunt squirrel, pheasant, quail, rabbits, etc. Also the more you use your turkey gun the more you will become accustomed to it. Good Luck again
