Actually I do have experience...both in 11 gauge "bess carbines" as well as in Pedersoli 30" 10 gauge SxS, which is cylinder bore, and improved cylinder choked...not on turkeys, but on upland birds, waterfowl, and skeet.
You might want to rethink your 10 gauge choice..., unless you have your heart set on an 11 gauge Bess carbine 'cause they're cool, which then defaults into that large gauge area, that's fine.
The reason being, bigger isn't always better. A 10 gauge ML shotgun is for waterfowl, since the idea is a) the bird is in flight and you are moving the gun b) the bird is about 40 yards away (less if you're lucky) and c) the bird has to be hit with enough pellets to penetrate through the
body feathers at 40 yards to bring it down since you can't count on a head shot. So you must use much larger shot, at least #2, or larger. What the 10 gauge gives you is more shot of the larger size, so if you're using 2 ounces of #2 lead (back in the day) that was launching 174 pellets, and because you're swinging the gun you'll actually toss an oval pattern. Great for geese on-the-wing, and with plenty of umph when those pellets get there at 40 yards from that cylinder bore.
Now with the turkey you must use #4 in most states, or smaller. You're shooting at a target on the ground not moving much, and you're going for a very small target, the head..., since them feathers act like a ballistic vest for the bird's body. Plus you're probably going for a closer shot. So if you use #4 shot in a 20 gauge you toss 168 pellets using 1¼ ounce of shot, which is almost the same number of pellets as the 10 gauge shooting two ounces of #2 shot. Remember no shot size restrictions a couple centuries ago.
But LD, how about shooting two ounces of #4 from the ten gauge, so tossing 270 pellets...., hmmmm? 
That's fine
on paper, but..., the ten gauge starts with a 21% larger opening, so the shot column in the 10 gauge barrel is
shorter and wider, and thus thee pattern starts wider too. So there are more pellets per ounce of shot in the center 1/3 of the 20 gauge shot column than in the center 1/3 of the 10 gauge shot column...., which is then offset by adding more shot to the 10 gauge...but how much advantage do you get ???.
So figure 270 pellets, take 1/3 for the center of the shot column and you get 89. Now adjust for 21% less in that shot column for the wider 10 gauge barrel, you get a potential 70 or so pellets you hope stay centered enough in the pattern to do the job.
Take the 20 gauge, 1¼ ounce of shot, and you get 56 pellets in the center 1/3rd of the pattern that you hope stay centered enough to do the job. So with the 10 gauge you're shooting 3/4 more of an ounce of lead, AND more powder,
to get an advantage of a mere 14 pellets.
For some folks that makes a big difference..., but for you, who can say?
This is all very crude, since it also depends on the actual gun. My 20 gauge trade gun loves #4 shot, but doesn't like #7 for distance. YOU may find that the paper model doesn't ring true for your gun shooting a specific shot size loaded a specific way.
"The pattern board doesn't lie." So you will in any case have to pattern the gun and try a bunch of different variations on the loads.
LD
