When you hear PRS guys say their ES is super small, say under 15-20, they are telling you one day, one group of five more often than not. When you hear an F-Class shooter tell you their ES is 20, they probably shot 20-rounds in one sitting. A lot of difference in the behaviors of the two groups. Its a matter of statistics, the more rounds you shooter, the larger it will be. Five rounds, or even ten rounds is not enough of a test to determine statistically significant numbers for ES/SD. One needs a sample of at least 30. Pulling up my Garmin, my last range session with my F-Class rifle, my SD/ES for ten shots was 6.3/21.9, 5.8/18.2, and 5.2/18.6 on three separate strings. If I combine them, I ended up with an ES of of 21.9 for 30 rounds. If I take the first five rounds of the first 10 round string, I would have had an ES of 5 and change.
