KY Jon,

You are right on the money, my testing with .410 shells shows the same thing yours does, and it can vary from gun to gun also. Now I just purchase the Win .410 shells off the shelf, making sure they are under 1275 FPS. I use the .410 for introducing my Gun Dog pups to gun fire, usually shooting Chukar for them after they do every thing correctly. When using the 2 1/2" shells to start out with, the gunner must be dead on the bird, having guys miss a number of kill shots with the old Savage O/U DT/DH gun, I started to investigate the shells I was using. Turns out the patterns were no where near consistent, so I started looking for different shells.

Ryman Gun Dog