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  1. In preparation for several major matches in the area, a club performed a chronograph check at a local match last weekend. About 6% of the competitors failed to meet their declared PF. This included several experienced competitors. So remember this! The average velocity (and hence PF) you measure at the range will always be better than the official USPSA chronograph results. Yes, it is true! The two measurements are like comparing apples and oranges. It has nothing to do with the small differences between chronographs and of course all the laws of physics apply equally in both cases. So how can I say that? It is strictly because of the number of rounds used to determine the average velocity in each case. To pass the official PF test the first time, only 3 rounds are used compared to 8 or more rounds we typically use at the range. The bottom line is that velocity is random in nature and the best way to understand and manage it is to use statistics. So statistically speaking, the term “better” means less uncertainty. We can quantify this uncertainty in terms of probability which can easily be determined from statistical tables. My post "Reloading to Meet PF with Confidence" located here ( http://www.brianenos...opic=229005&hl= ) illustrates the problem and provides a very simple solution. Also in this post, there is an example which compares the probability of being at or above the same average velocity in each case (at the range versus a USPSA chrono). Using 8 or more samples the result is at least 97.3%, but using 3 samples the result is only 85.2%. And it is important to note that the two results can be much farther apart. A seemingly obvious solution is to just chrono your ammo using 3 rounds. The problem is that using only 3 samples causes wild variations in the results and you will drive yourself crazy trying to get any type of consistent measurement. The good news is that the link above provides a very simple solution to avoid this problem. For a better explanation and more examples, see page 70 of the Jan/Feb 2015 edition of FrontSight Magazine.
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