Thread: Obtaining more information from your groups - overlaying groups

We have established that if you wish to make accurate statements about the precision or mean point of impact of your rifle system, then larger quantities of data are required than can be reliably obtained with the individual 3-5 shot groups that many people used to commonly shoot. Note that purpose here - making accurate statements about the precision/MPOI of the system. If you want to tell me this is irrelevant for normal hunting use: you are correct, you can stop reading and close the thread now.

The purpose for collecting more data is to have a better understanding of where your first shot will fall in a future scenario. A rifle system does not put every shot in the same place. It produces a cone of fire, and any shot in the future may fall anywhere within the circle described by that cone. 3 or 5 shots taken alone do not reliably tell you enough about that cone to accurately predict where a future shot will fall. This is well established and demonstrated. The average extreme spread measurement of multiple small groups doesn't give you information about the relative position of each shot and as such, is less informative.

I've developed a spreadsheet tool with tabs for overlaying up to 3x 10 shot groups, 6x 5 shot groups, and 10x 3 shot groups, to give a 30rd aggregate for each. This allows overlaying of multiple smaller groups and extracting information from every shot to get a more precise measure of the precision and mean point of impact of your system, if you don't want to shoot 10-shot strings on the same aiming point at one go.

This spreadsheet will give you:

- A visual overlay (scatter plot) of where all your shots fall across multiple groups
- A calculated mean radius value, to give a more accurate measure for the precision of your system
- A calculated mean point of impact so you can get a better zero.

It can be obtained at: https://filebin.net/x3rj8yovx6sd0aqu

INSTRUCTIONS:

Fire up to 3x 10 shot groups, 6x 5 shot groups, or 10x 3 shot groups, OR use previously fired targets
NOTE: All shots must have a common fixed point of reference (point of aim) - there can be no sight adjustments between shots

Use the Hornady Group Analysis App (or Ballistic-X or other group measure apps) to obtain the X (windage) and Y (elevation) values of each shot


Enter these into the relevant columns in the spreadsheet



All the fields and the scatter plot will auto-fill. The scatter plot is "corrected" to centre all shots around your mean POI.




So, if you shoot a series of 3 round groups like this, which are individually not very informative - you can now obtain more information from these.



I've already shared an earlier version of this with @Tentman, @flock, @McNotty, @zimmer

I would be interested to see other's results if anyone has a play.