Patterning a Shotgun

One of the best steps a shotgunner can take toward assuring hunting success is to pattern his gun with the various loads he intends to use in the field or blind.  It's not hard, and it really pays off.  The pattern percentage of a shotgun is the number of pellets it puts in a 30-inch circle at 40 yards divided by the number of pellets in the charge.  If 70%, it is designated full choke; if 60%, modified; if 50%, improved cylinder.  To determine the percentage your gun delivers, tack up a large sheet of paper at 40 yards, fire at it and swing a circle of 15-inch radius around the greatest concentration of holes.  Count the holes on or inside the circle.  Then count the number of shot in the type of shell you used and divide it into the number of holes to obtain your percentage.