Craig, in your last paragraph about the depth of the crimp or possible primer substitution, Joe Wood loaded that exact recipe but doubled the powder and if you look at his post with the picture you will see it did not or could not crimp.
Also unless it was a magnum primer such as a Federal 209M or CCI 209M the increase would not be substantial.
I posted on Shotgun World on the Reloading Forum and received many response about dropping a double charge in Mec Progressive machine.
Some said yes, but one poster said this "Powder does not fill the bar of a MEC until the bar goes fully left, it drops the powder when it travels toward the right.".
If there was a powder bridge in the tube, the shot would not have fallen in the previous load, or everything would have fallen.
With most of these newer components, there is minimal wad pressure, mostly less than 20 lbs. If there was a double charge of powder and IF the shell crimped the wad legs would be crushed and you would have to use close to 100 lbs. wad pressure, but you would see that before hand.
