A good number of turkey loads use #6, usually hardened, plated and buffered.
Try
http://www.winchester.com/products/c...shotshell.aspx
the tool bar on the right lets you choose the use. #6 comes up in everything from rabbits, squirels to ducks to turkeys.
I personally would not use #6 for HD, it simply won't penetrate enough, particularly through heavy clothing. It would leave an absolutely gross wound through through a t shirt though!!!