

Rifle and pistol groups  quick measurement, analysis
& archive
Online
version now available! Try it now . . .
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ShotgunInsight made measuring shotgun pattern
targets easy. By automatically counting pellet marks and performing
rigorous statistical analysis ShotgunInsight made possible in minutes
what was otherwise near impossible. ShotgunInsight is helping to
reveal the secrets of shotgun patterns that have been hidden for over
100 years.

Rifle and Pistol Insight provides a similar
benefit to rifle and pistol shooters. By calculating the statistical
spread of the shots a much more reliable estimate of the true
performance of the gun and bullet is found. The traditional measure of
extreme spread is quick and easy, but often misleading.
Why Rifle & Pistol Insight should be used . . .
The traditional extreme spread measurement can be
very misleading!
"Loose group" shot
on 1" x 1" grid. 
"Tight group" shot
on 1" x 1" grid. 
"Loose group" with
extreme spread shown.

"Tight group" with
extreme spread shown.

The average spread measurement is more useful (but hard to
calculate by hand) . . .
"Loose group" with
average spreads and average radius shown. 
"Tight group" with
average spreads and average radius shown. Note the smaller indicated
group compared to the "loose group". 
Calculating the average spread is time consuming by hand, but
easy by computer . . .
Hand calculation of average radius.

Measure the horizontal distance of each hole from the edge of
the target.

Add the distances and divide by the number of shots. This is
the average horizontal distance.

Repeat for the vertical distance from the bottom of the
target.

Mark the average horizontal and vertical distance on the
target. This is the average Point of Impact (POI).

From this average POI measure the distance to each hole.

Add the distance and divide by the number of holes. This is
average radius.

Want the horizontal variation (standard deviation)? Repeat
steps 5 & 6 but measure each horizontal distance, square it,
add them altogether and divide by the number of shots minus one.
Square root this number and you you have the horizontal standard
deviation!

Want the vertical variation (standard deviation)? repeat step
7 for all the vertical distances compared with the
average.

Want the standard deviation of the radius? Repeat step 5 but
subtract the average radius obtained from step 6 and square the
resulting distance for each bullet hole. Add all these squared
numbers together, divide by the number of holes minus one then
square root the result. You now have the standard deviation of
the average radius!
. . . Earlier generations
of shooters couldn't be bothered doing all the above steps. Now, thanks to computers
and digital cameras you can get all the above quickly and easily.

Rifle & Pistol Insight calculation of average radius.

Take a digital picture of the target.

Load it into Rifle & Pistol Insight.

Mark the holes. (blue dots on the above targets)

Indicate the known horizontal and vertical distances. (green
arrows on the above target)

. . . that's it!


