Guys I too used to laugh quietly at people who weigh their pellets, wash them lube them etc.etc. Admittedly, I will never do this on an ongoing basis for my needs but I did do it once and was shocked at what I found.
After fitting an Altaros regulator to my S200, I was keen to find out just how consistent it made my power output. I therefore decided to eliminate any variables by weighing and grading just 100 pellets for my test. Now according to the label on the AA Diabolo Field tin, 8.4 Grains is 0.547 grammes. According to the converter on Google, it should be 0.544 Grammes !!! Already a discrepancy. Well, I cleaned them and then started to weigh them ... arranging them neatly in stacks of .02 Gramme intervals. The resulting picture was a near perfect but shallow Normal Distribution curve with the minimum weight of a pellet coming in at 0.490 grammes while the heaviest pellet was a whopping 0.620 grammes !!!!
So assuming my regulated S200 was putting out a perfectly consistent speed of 780 feet/second, the resultant spread in foot pounds energy would vary between 10.22 ft.lbs for the .490 gramme pellet to an illegal 12.93 ft.lbs for the heavier .620 gramme pellet. The resulting variation in POI at say ... 40 yards does not even bear thinking about. Or in other words, if the power is consisten (which it would be with a well regulated rifle) the speed and therefore the POI will shift dramatically with a standard un-sorted box of pellets. Makes you realize why they grade it when you are seriously into winning competitions and matches.