First thing you need to do is check your state's regulations. Tennessee doesn't allow turkeys to be hunted with shot larger than #4. Then of course you need to get a pattern on it with whatever size shot you want to use.

I kinda agree with the rest, improved cylinder may be a little weak. I use a standard full and 40 yards is pushing it for me. But I can tell you this, the preacher at our church started turkey hunting 3 years ago and has tagged 6 turkeys with a modified choke without missing one. He said his max range is 30 yards. Needless to say I'm camping at his house this spring.

One other thing.... Why do you want to use bismuth? Usually folks use lead or hevi shot for turkeys.