During the testing for “The Truth About Shotgun Ammo” I learned it’s important to count pellets in a shotshell before you pattern.
Before we patterned any load we took three shells from the box, cut them open and weighed the payloads and counted the pellets. The results were surprising. Weights were consistent but pellet counts were not. Not all pellets of the same size are the same size. Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI) specs allow variations up to .010” in pellets of the same size.
That small difference in size can add up to a lot. For instance, the pellet counts in a 3 ½-inch, 2 ¼ ounce load of 4 shot and a 3-inch, 2-ounce load of 4 shot were almost identical even though the heavier load should have contained about 35 more pellets. Despite that difference, pellets in both boxes of shells were within spec.