Good post, Miller. Glad to hear you are feeling up to some shotgun research. Have you read "Performance of Sporting Shotguns" by Dr. Andrew Jones? He answers a lot of questions.

Shotgun patterns follow a Rayleigh distribution, which can be nicely approximated with a normal distribution. The Rayleigh distribution describes rifle groups, artillery fire, and bombing patterns, also. The fact that the shotgun launches its projectiles at the same time is irrelevant. There is so much variability from one pattern to the next for the same gun and load that 10 patterns are necessary for reliable statistical analysis. Said analysis is sufficiently complex that a computer is pretty well mandatory.

Jones produced a program, Shotgun Insights, to analyze digital photos of patterns. It works magnificently. He was able to investigate 250 (2500 patterns) combinations of gun/load/choke.

Before meeting Jones, I shot patterns on paper and drew a series of concentric rings and radial divisions (think pie slice shape) with all areas of equal area of 5 square inches (think a edge on clay target). Analysis led me to the Rayleigh distribution. And, this led me to the startling realization that all patterns, on average, are the same.

Before anyone has a heart attack, let me explain. Patterns sweep out a trumpet shaped volume. Choke effect controls how quickly the pattern spreads radially; a plot of forward velocity vs sideways (radial) velocity rotated makes the trumpet shape. So, if you look at two patterns from widely differing chokes and shot at the distances where the patterns have equal diameter, you will find the patterns are indistinguishable.

There is no such thing as central thickening. It is only recognition that the center areas of the pattern will always have a higher pellets per square inch than the outer areas. Patterns never have a smooth, even distribution. That is fortunate, indeed, or shotguns would be short range shooters. Fortunately, the Rayleigh distribution has plenty of pellets in the center area to feed into the outer areas as the pattern moves forward.

Praying for your speedy recovery daily, Miller.

DDA