Non- reloader
Try different loads in your gun at the distance you want to shoot is the easy answer.
Remember a couple of things:
-What "choke" a fixed choke bbl or choke is marked is NOT a guarantee that is what is will throw. ( two exact guns, exact same choke , with exact same shotshell right down to the same box /lot # will most likely throw different patterns. [ FWIW folks will shoot a gun load combo of a friends and either like or hate...if they like they buy , if not they hate...never patterning or learnig this...lots of errornet thngs get started like this " don't buy that gun it throws donut patterns..."]
-" Matter of bore not choke"
Remember we are asking a bunch of shot to squeeze past a Forcing cone, down a bbl, and out the end of a constriction...of some kind...either none or a bunch...(from cyl to ex full).
-Shot gets deformed , deformity causes shot to do weird stuff. Soft shot like in inexpensive dove / quail loads, will have a more open pattern and long shot string. Hard shot ( more antimony) will have better /tighter patterns, shorter shot strings.
-If the load is too fast - donuts can occur.
-If the load is too heavy - donuts can occur
-If the screw choke is : not concentric, too tight ( don't care what marked remember?), Forcing cone is to sharp a buch of pellets are going to become deformed when the pressures of a grenade ignite this load.
- Before we had screw in chokes, we learned a bunch of this stuff easier. Pattern the gun with a variety of loads, when you find a load that works at the distance for the task buy a bunch of that loat #.
- Forcing cone work will most often do more good that choke work or buying other chokes.
My gut feeling?
Your donut patterning, and having not seen it...I think the forcing cone is too steep. Another loading will help, perhaps the Winchester loading with a grex buffer ( to help prevent defomity of shot).
If turkey season is close and no time to for the work...try a bunch of 5 packs, eeven som 1 1/8 oz, 1 1/4 oz. You want "X" number of pellets of say #4 . #5 #6 shot at 30 yds to hit the vitals.
It don't have to say "turkey" on the box..."Tom can't read" ...course you ain't gonna have him get that close to try anyway - right ?