How to measure groups size???

C

chadflys

Guest
Just wondering how to measure group size. I have always measured the widest hole spread. Which if I put stacked five on top of each other I'd have the width of a .22. How is it that I have read some groups of being less than .22? I'm presuming they are subtracting the width of a .22 to get sub .22 numbers. Is that the correct way to measure?

Thanks,

Chad
 
They are subtracting the width of a .22 to get their group size. When I'm at home comparing groups I don't bother with all the subtraction, which is fine as long as you always do it the same way. Apple to apples.
 
There's an easy way to measure groups that I've heard is very accurate. I would assume it is considering how it works. There's a computer program called "On Target". It's a free download. You either take a photo of your target or scan it in a scanner and enter it into the program. You enter the bullet holes, the size of your bullet holes and the size of a reference (like the distance between rings or anything you know the size of) and the program tells you what the size of your group is. I've heard this method is pretty accurate. Of course they use calipers at competitions but since you can zoom in on the groups I would think the computer program would do very well.

Others may have a different opinion of this program but the logic of it seems sound to me. Maybe it's because I've been making a living with computers for a long time but I trust the results of this program. I've tried to measure the groups manually and the results are always very similar to what I get with the program.
 
I've used On Target and its great. It can give you more information than just extreme spread. I saw it demonstrated for the first time this summer at the PSL in St. Louis.

PS. I've attached an output of a typical ammo test.
 

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If you

shoot groups a lot, you may consider buying a group measuring devise to put on a caliper if you have one. You can buy them from Hart and son or Sinclair I believe.
 
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