Meant to add, you will find that 1¼oz in 10ga, 1 1/8oz in 12ga, 7/8oz in 16ga, 3/4oz in 20ga & 5/8oz in 28ga "All" have shot column lengths in their respective bores of between the 12ga dia of .729" & the 10ga dia of .775". You will also note these were the most common loads in the period when shotshells first began to be loaded as commercial products. These loads had nothing to do with round ball weights or Sq loads, but were suitable to the burning rates of the powders being used, & length of shells being loaded.
The Sq load theory is mostly the imagination of some writer Eulogizing his favorite gauge, & is nearly always misapplied anyway.

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