Winchester Supreme High Velocity or their XX turkey shells are pretty good. I think they shoot 1 1/2 ounce of shot and come in 4, 5, or 6 shot. I am sure there are other 2 3/4 inch shells that would work, especially if you are only going to 30 yards.
Either of the above shells will have enough pellet energy to kill a turkey out to 45 yards (in any shot size 4, 5, or 6). But you MUST also have the pattern density. A turkey is shot in the head & neck but the vital area that actually kills the turkey is the skull and vertebrae of the turkey. This is a considerably smaller area than the head & neck. I like to see a pattern dense enough to give me 4 or 5 hits in the skull & vertebrae at my max range to kill a turkey. I use 6 shot.
My pal Skully here shows you the vitals on a turkey and you can eliminate the beak and the eye socket area.