Let's ignore that nasty forcing cone thing used to transition pellets from shell in the chamber to bore.

1 1/8 oz. shot in a 10g (.775") - 12g (.729") - 14g (.693") MLs without choke constriction will yield essentially the same pattern.
1 1/8 oz. shot in a 10 - 14g MLs, each with the same .030" choke constriction (bore ID minus muzzle ID) will yield essentially the same pattern.
Too narrow a bore (and I don't know what that would be) causes elongation of the shot column = more pellets in contact with the barrel = more deformation = deterioration of the downrange pattern. Or maybe not with steel shot.
Too big a bore (and I don't know what that would be), unless the appropriately oversized wad was used, would be associated with gas 'blow by' which disrupts shot charge on exiting the bore = deterioration of downrange pattern.

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