Not Ted, but a slug normally is of lighter weight & with a higher velocity than the standard shot charge for the gauge. Thus bbl times are different & undoubtedly bbl vibrations are also different. If the load "Always" went to exactly where the bbl was pointing at the instant the trigger was pulled all doubles would cross-fire & would never hit point of aim.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra