Some Observations of the Red Rifle with 12-pin.

The 3 25-shot targets fired with the Red rifle and 12-pin are unusual because with an identical configuration, the rifle shot both the most accurate target (#3) and the worst target (#1) of the 12 target total.

Is this the perfect example for illustrating how variable groups can be in rimfire, in even the most controlled settings?

Or, was there an unknown factor which contributed to the anomalous results?

Anomalous is too strong a description, but there is a significant statistical difference between Target #1 and Target #3 and after analyzing hundreds, maybe thousands of large groups….I’ll tell you it’s a very rare occurrence to see significant differences with 25 shot samples. Keep in mind I’m referring to the things we’re most curious about that display small differences in results, and “not” a comparison of a factory 10/22 to a purpose built BR rifle.

Target #1 had a GAP generated “Width” of (0.252” +/-0.066”) and that produces a range of (0.186” to 0.318”) for predicting the true accuracy and making comparisons with other results to show statistical significance.

Target #3 had a “Width” of (0.145” +/-0.032”) and a range of (0.113” to 0.177”).

Because those ranges don’t overlap, it means those results are significantly different.

Here are 2 screenshots showing the GAP analysis of the targets in question:

For those statistically challenged ARA shooters who I’m about to lose because the charts above have shocked your mind into apathy, here are the same targets with the shot locations moved to the center of the 100 ring on the ARA target.

These might be considered a visual and scoring depiction of statistical significance, with a target everyone is familiar with.

Now comes the difficult part. Will there be something Dan remembers about that particular target that might explain it? If there isn’t, can I revisit the data and discover something I overlooked?

Here’s the response I got from Dan when I asked about this target:

Not sure why target 1 was not nearly as accurate.  Owner of the rifle was not pleased with the performance on target 1.  It was the first target of the day, and the rifle had been in the pickup all night so it was cold.  That morning was down into the 30’s.  The temperature was the only variable that I could find that might have caused the decrease in accuracy.

It's certainly revealing and quite a coincidence that it happens to be the first target of the day with a cold rifle that results in this poor target, but I don't normally see quite this severe a degradation of accuracy when I test under the same scenario.

The plots below, which my spreadsheets automatically generate with every target I shoot, may show some contributing factors, but no definite cause for the poor performance on the first target. They are velocity on the x-axis and its correlation to vertical on the y-axis.

Target 1 shows a stronger correlation to vertical with velocity than does target 3, but plots and correlation equations can be deceptive or open to interpretation both visually and mathematically. In this case, if you were to throw out the strange very low velocity shot on the first target and scale both plots with identical ranges for vertical on the left and velocity on the bottom….they would look more alike but still display a difference that should be noted.

If your definition for a rifle being in tune, is its ability to shoot a large spread of ammo speeds without producing vertical on the target, then correlation numbers near zero would be your goal.

Is this rifle in “tune”? I honestly don’t know because I’ve never got a correlation number that will consistently stay near zero and there is a dearth of data from any sources other than my own testing results.

If you use one of the links I’ve posted on this blog to the Border Barrels website, you’ll see some of the research that Dr. Geoffrey Kolbe has done on this same subject. It’s also a great source for a lot of rimfire related matters.

I’ve got one more chart to present which may bring up even more questions I don’t have an answer for. This is a plot of the Std Dev of the ammo across the chrono for each target and its correlation to the GAP calculated accuracy of each target.

The Std Dev of the ammo used for the first target is 12.8 fps and it resulted in a GAP width of 0.252” (worst), but the same ammo and same rifle also produced the lowest Std Dev and smallest group (best).

By the strictest definition of “tune”, this might suggest that neither rifle was in tune but with so many combinations of rifle and bolts along with a few other variables that might skew an analysis….I’m not confident in making any conclusions.

Under “Mission Statement” in this blog, I said I was “clueless”….now you know why. LOL



Landy