First off I'm gonna blow your theories out of the water. And since you mentioned the magblends I know your talking about Hevi-13 loads and #7's in those loads spreading out faster. First off I shoot Hevi-13 3.5" 2.25oz #7's in my Moss 835 and Star Dot choke. And this pattern here should prove at a tape measured 40yds that they don't spread out faster.
Now let's blow your other theory to heck when you say 7's don't have the kinetic energy out past 40yds. I shot this bird right at 50yds. But it was'nt with my 835. I shot it with my 870 3" with Hevi-13 3" 2oz #7's and let me just show you the damage those little shot did that remember your words lack kinetic enery at this distance.
But first let me show you a picture of how the box of 7's was shooting out of my 870 and MAD Super Max .675 choke to help you see what kind of pattern slammed into that bird. That bird by the way was a 24lb gobbler. This was a 10" and 20" circle. There's over 500 shot inside that 20" circle which is simply amazing if you know anything at all about patterning these loads.
Now here's the damage.
Keep in mind this one below was the side I shot him on. I aimed at the bottom of the neck once he got close enough I knew I could kill him I shot since I was hunting public ground and I know how easily another hunter could mess my hunt up.
I would say a lot of shot that hit the neck were complete pass throughs. Try that with lead #5's at 50yds and let me know the outcome.
Now here's the other side of the breast that some shot went all the way through and out this side.
And if that gobbler could speak, he would tell you those Hevi-13 #7's are one bad momma.
