IMO, if you're not handloading, look no farther than the 20ga Federal Heavyweights in #7 size shot. Unlike most turkey loads with a 1 1/4 oz payload, these are 1 1/2 ounce. And, like no others, these are using even "heavier" shot. Those #7's will penetrate better than a #5 lead.
It's possible you can find something that patterns better, but the odds are already in favor for these, especially when you balance pattern density against energy per pellet.
Not to say those Hevi-13 Magnum Blends aren't good, also, but these Federal #7's are going to have the per pellet energy close to a #6 Hevi-13. And since the Feds are 1 1/2 ounces, about the same # of pellets you would get in a 1 1/4 ounce load of Hevi-13 straight #7's (or more pellets than should be in a Magnum Blend).
