Larry;
Area of a circle is proportionate to the square of their diameters while circumference is proportional to their diameter.
Thus if we loaded both a 28ga & a 12ga with shot loads of exactly the same length the 12 ga would have a 75% heavier shot load, but would have only 32% more bore contact, so yes the smaller gauge will have more shot in contact with the bore.
As shot cups have done so much to reduce barrel scrub I did not go into this aspect. Many modern plastic wads also do a better job of cushioning the charge to help reduce shot deformation from setback as well.
These factors along with the development of progressive burning powders is in fact what has made the small bore shotgun a viable option for so much of today's use.
Very good point at the end, Miller. Combine a good wad with hard shot, and smallbores are likely to throw much better patterns today than they could back in the day.
