Well the concept of choke surfaced in the early 1860’s and was perfected and patented by W.R. Pape in the late 1860’s. Neither the concept nor the application are a mystery today. There are near endless variables that can affect patterns, but for those that must split hairs, nothing provides as much useful information as actually patterning specific ammo in a particular barrel at a specific distance. How you use this information will be the key to finding the results you’re looking for.
Strangely, after 150+ years of use, choke is still one of the most misunderstood concepts of shotgunning. And during all those years there have been hundreds of articles and many dozen books written on the subject of choke, most, even the oldest ones, use examples, drawings and actual numbers to explain the principles of choke. One of these more modern examples from 1930-1990 will clear up the mysteries of choke.