Even Patterns - Myth, Art or Science?
The elusive perfect pattern.
These patterns were borne of legendary 16 gauge shotguns created at the turn of the century. Double barrel shotguns that were created by a British alchemist 93 years old. He began his career as an apprentice to a master gunmaker at the age of 6. His shotguns were legendary. The patterns were so beautiful that they could kill without fail everything from goose to sparrows at incredible ranges. ( nothing but #5ís)
That is a myth for your consumption.
The role of experience.
Guns are modified every day by people with a great deal of experience with shotguns. They have seen the effects of various changes on the performance of a shotgun. These people have an insight or an intuition about what a "better" shotgun should do. The specialties range from the card shooters with their scoped shotguns to Olympic skeet shooters and their barrels for their sport. Experience. What works and what doesnít work.
Just the facts maam, nothing but the facts.
The distribution of shotgun pellets in a shotgun pattern can almost always be described as Gaussian. That means a graph of the number of pellets/unit area versus the distance from the center will almost always be in the form of a bell curve.
What if I told you all stop signs are round? Generally speaking this would be true. We all know that they only approximate a circle by being an 8 sided shape. If they had 16 sides it would then be closer to the exact truth. This is a useful perspective for understanding the description of shotgun patterns as gaussian.
The pellets mostly fly off from the shotgun in a random manner. The pellet distribution is a bell curve about the center of the pattern. (Roughly, Just like a stop sign is roughly a circle.) That being said, just because it is shaped like a bell doesn't tell everything. We can have a tall and skinny bell as in the case of a Full Choke or a short and fat bell in the case of a Skeet choke.
Oberfell and Thompson produced a couple of methods of operationally measuring patterns for the purpose of comparing evenness.
Simple, Exact but not too Useful
They created a table that used pattern percentage in conjunction with the ratio of 30" count to 20" count to provide a ratio that could then be used to look up the classification of the evenness of the pattern. This resolved into ratings of excellent, good, fair and poor. This was a rather limited result in my own experience since so very many of the combinations I have tested were all classified as "Poor" patterns.
Complicated, Inexact but probably more useful.
Oberfell and Thompson produced another method of determining evenness based on their ability to find places where 5" circles could go into a pattern without encountering a pellet hit. They then come up with some charts to grade the patterns based on the number of 5" circles they found in a 30" circle. This was a notable attempt to operationally define a measure for comparing the evenness of various patterns. The reason that this method was inexact lies in what is known as the "Packing Problem". Simply stated the number of 5" circles that a blotchy pattern would hold depended on how you packed them in there. Those persons more skilled at packing their suitcase had poorer patterns than those not so skilled persons evaluating the same patterns.
Enter the computer.
Much more complicated, Exact, and useful.
What Oberfell and Thompson would have given for a good desktop computer and digital cameras. I wonder that they perhaps discussed many ways of looking at shotgun patterns, that would have taken so much effort to try on a large enough sample, they simply gave up on them. The "True" Shotgun Factors take advantage of the power of the computer to overcome time limitations and go straight to a much more involved series of measurements for an applicable measurement that is both exact and very useful. The computer makes complicated and time expensive calculations and measurements "Free".
Since the calculations are free we can count the number of pellets in a large number of predefined and pre-positioned target shaped areas within an area of interest on the pattern itself (Overlapping is a good thing). In this way we accomplish defining an exact operational method that delivers the 5" circle goals and bypasses the "Packing" problem. The process involves a great deal more calculations, but it creates a straightforward result. You broke or killed a certain number of targets from within a large number of targets modeled within each pattern.
Were we to use say a 1000- 5" circles for a 30" target we would approximate the ability to compare patterns that was found by the good packer in Oberfell and Thompson's example. (Obviously not in the same scales)
The true factors give us another measure to compare one pattern with another. Many of us have wanted to put our finger on what an even pattern is. Many will say that they know what it is when they see it.
The True Factors give us a standard way to move forward with changes that take the mystery out of evenness, and replace it with a straightforward number applicable to our particular sport.