I have never had much luck with "mixed" shot...seems the heaver shot try's to overtake the smaller shot in flight and destroys the pattern, it's never consistent ...just like the so called experts said would happen.
Like many others, my mind kept telling me this is a great idea and I simply don't believe it won't work, besides many people are telling me this makes a great hunting load.
Then I started actually using a large sheet of butcher paper, marked like one would a 36" round pie when cutting it, or 7 equal parts within a circle with the center of that circle being your aiming point, I could actually count the number of hits, and where they were hitting....quadrants, I believe is the term.
Seems the experts were right. Mixed shot ie, 5's & 7's never showed a consistent pattern...straight 5's or 7's improved the pattern and was much more consistent.
Now, having said all that, I have to say your mileage may vary with this, considering different barrels, gauges, amount of shot, and chokes, along with wads, cushions, powder charge, etc, etc,....and I have add that pattering your smooth bore is actually a very pleasing thing....a real eye opener that will actually put you a step closer to really knowing your smoothie.
Uncle Russ...