I have something with new loads to give me piece of mind beyond counting pellets on paper. With your dead turkey, make a slit down the neck a little ways. Put the garden hose up under the skin pointing toward the head and turn it on. You will quickly get a feel for how many pellets are actually hitting the bird where you want.
I also like the radiograph (Xray) a bird post mortem as well, although I realize most folks don't have access to that. My lead shot turkeys had impressive numbers in the head and neck on the Xray, Hevi 13 had less and HW 15 even less. That was a function of the pellets passing on through though. You really don't want a lot of retention.
