Some of the more substantial changes came along this year when I started to look for better ways to evaluate my performance. One of the most significant things happened was being introduced to On Target TDS. I had already been using the free version of On Target to measure my groups. My friend at U.S. Optics got me in contact with Jeff Block, the person who wrote the On Target program. I spoke with Jeff a few times about his premium program, On Target TDS (Target Data System). He wanted some input from me on how to improve it, and actually incorporated some of my suggestions, one of them being the feature that I’ve been using to make composite target composed of shots from different target and shooting sessions.
Jeff also told me about Ballistipedia. We’d been talking about statistics, and how to integrate his program into something that would run more powerful statistical analyses. I was not able to figure out how to make that happen, but the Ballistipedia site had some information about different statistics, and advantages and disadvantages. This was finally the “aha” moment for me that measuring group size using extreme spread wasn’t telling me very much about my total performance.
What’s strange is that I had already been introduced to other ways of measuring, and was aware of mean radius. I’d known about that for quite a while and just ignored it. John Simpson’s book (Sniper’s Notebook), which I’d gotten in 2013, discussed that and other statistical measures, such as CEP (Circular Error Probable), the 99% circle, radial standard deviation, and probably others. Sometimes it just takes one thing to finally click things into place. In this case, it was a description in Ballistipedia of the difference between invariant measures (Mean Radius, CEP, Variance, Standard Deviation) and range statistics (extreme spread, diagonal, figure of merit, covering circle radius). A big difference between the two is that invariant measures “do not vary with group size. I.e., taking more shots tightens their confidence interval but doesn’t change their expected value,” while range statistics “increase with group size. They are more commonly used because they are easier to calculate. But they are statistically far weaker because they virtually ignore inner data points.” (Quoted from the page at Ballistipedia linked above.)
Last spring and summer I went through an obsession about my precision. My rifle would almost be sub-minute for a few shots and then one would just go crazy. It makes a person go through a quasi-bipolar emotional cycle with the rifle. Using extreme spread as a group measure exacerbates this, as it only measures the worst shots. Statistically speaking, the very worst shots are less likely, so you might see a decent group or two before things go completely haywire, which for me made me start thinking I’d finally fixed my shooting problem (which turned out to be a rifle problem), before having my hopes smashed against the rocks with a wild shot.
When using what Ballistipedia describes as an invariant measure, the outlier really won’t affect the numbers that much. It’s just part of the total performance. Additionally, it’s easier to spot small differences in performance over the long term, for example, between the 155 grain Amax and the 168 grain Match King.
Since I’ve been primarily using mean radius to evaluate my performance, I’m much more practical and even keeled in evaluating my shooting. Realizing that “dispersion happens” has really removed most of the emotional baggage that I still see most shooters dealing with. I feel sorry for them, but it’s hard to get people to realize sometimes how something just a little different can change how they think and feel about things. Sometimes, just a little different perspective from which to view things can make the picture so much more clear.