I would try to find a 2 3/4 inch turkey shell that would give me an adequate pattern out to my intended maximum range. Avoid the 3 1/2 inch shells which have brutal recoil. I use them and they throw good patterns but WOW. They will slobber knock you. I think that Hevi-13 and Winchester Elite Extended range shells come in a 2 3/4 length. Since you are starting with a reduced amount of shot because of the shorter shell I'd get them in number 6 shot. Denser than lead 6's will kill to 40 yards easily if your gun will throw a dense enough pattern. 6's will typically out pattern 5's or 4's. And denser than lead shot will out pattern lead by a wide margin. Shoot at a dot centered on a large sheet of paper so you can see what the whole pattern is doing. Poster paper size at least. Typically 80 to 100 pellets inside a 10 inch circle is considered a good pattern. Whatever the maximum distance your gun can hold that dense of a pattern then there is your maximum range. Guns vary as do their performance with different chokes and shells. So I cannot tell you what your maximum range will be from your gun with 2 3/4 inch shells. Get a good extended range choke approved for use with hevi type shot and try the shells I mentioned and I'm betting that will give you more range than standard lead shells. But at the end of the day if you had to choose between limiting yourself to 35 or even 30 yards rather than risk serious injury to your neck? Well obviously your health is worth more than every turkey on earth heaped in one pile. Error on the side of caution.