This discussion on shot size made me remember something I had read in an old book titled "Hitting vs Missing With the Shotgun" Written by a Ruffed grouse hunter in 1898, S.T. Hammond.
In the book he says,

"The charges that I have used for many years in a 12-gauge seven pound cylinder bored gun, with entirely satisfactory results, are, for the right barrel- which I nearly always use first- three drams of good black powder with five-eights of an ounce of No 10 shot, and for the left barrel the same amount of powder with seven-eighths of an ounce of No. 8 shot. These charges give good penetration and pattern, while the recoil is scarcely noticeable. I do not give these particulars as a guide for anyone to follow until it has been shown by actual experiment that these charges are the best that can be found for the gun in use. Many cylinder bored guns will do good work with these
charges, while with others the performance is not at all satisfactory."