HOW ABOUT THAT! :hatsoff: I am glad to hear that my suggestion seems to have paid off. At 20-25 yards it ought to be devastating on any turkey. And without all that kick, you won't have any trouble lining up the shot, and sending it dead center on that head and neck.
Please give credit to the lat V.M.Starr. I read his stuff years ago in Muzzle Blasts, and noted at the time how different ballistics must be in ML shotguns than in modern guns with their chokes. I thought he made sense long before I every bought a ML shotgun myself. I was thrilled to find his article on the Bob Spenser site, which I found from his forum.
I use round ball loads with similar powder charges and wads to check the velocity expected with a shot load, as everything I have read tell me that is about as close as you can get. If I shoot shot over the chronograph, even with it being close, the wads cause a fairly unacceptable variation in readings from shot to shot. So, its the round ball equivalents, or referrence to factory tables for similar loads. I do use the pellet energy tables in the Lyman Shotshell reloading manual, to give me an idea of retained energy at 20, 40, and 60 yds for each pellet with the columns providing both velocity and pellet size. I have killed pheasants stone dead out to 30 yds with my open cylinder 12 ga. using 2 3/4 drams of FFg, and 1 1/4 oz of #5 shot. A pheasant is much easier to kill than a turkey is, But I chose the load because it had been the favorite load of the Commercial Duck Hunters back in the 1880s on the Illinois River, and I am impressed with how the #5 shot's retained energy even at 35 yds smacks the bird down out of the sky with any kind of hit. They also seem to pattern well in my gun, producing round patterns, albeit very open.
Thank you for the info. I hope this will also help others. BTW, years ago, my best friend worked on developing a turkey load with his 20 gauge fowler, and he tried every size shot from #2 to #7 1/2. He also settle on Number ^ shot, for the same reasons you have found. Out to 25 yards, there are so many pellets on the target you almost can't miss killing a turkey with that load inside 25 yards. He got his bird, too.
Best of hunting to you.