Specialty Pistols
Measuring group size

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June 21, 2020, 10:50 PM
Measuring group size
Many years ago, I read an article where someone had compiled data regarding group size of 3, 5, and 10 shot groups. Basically, they calculated that a 5 shot group would be xx percent larger than a 3 shot group, a 10 shot would be xx percent bigger than a 5 shot group. Does anyone recall such an article or have an knowledge of those percentages?

I seem to remember that a 5 shot group was typically a third bigger than 3 shots, but can't recall for sure or what the 10 shot group would be.

Thanks in advance...
June 23, 2020, 01:10 PM
Interesting. Hopefully some one comes up with the article. I would like to read it.

One issue I always run up against is heating effects and how long in time do you want to spread out your group (3 quicker shots or 10 shots over a couple hours or rapidly fired)?
I've got a barrel which will always print the first two on top of each other and the third drops a couple inches at 100 yards.
June 23, 2020, 09:21 PM
I can't address heating up the barrel. For me, 10 shots in 2 hours wouldn't work because of changing winds or humidity that would skew the results.

I think the original article was in Precision Shooting magazine circa 1985-1990. A renowned shooter set up 3 targets in a row with one behind another, spaced only a couple inches apart, so a bullet would pass thru all 3 targets. Using a rail gun or some very heavy rifle from machine rest, the shooter fires 3 shots into the target center. Bullets pass thru all 3 targets, leaving 3 identical groups. The shooter quickly removes the last target, fires 2 more shots and removes the rear target which now has 5 shots. Then he shoots 5 more shots into the remaining target. The result creates 3 shot, 5 shot, and 10 shot targets that record the increasing group size as additional shots are fired.

As I said, this was 30+ years ago. I'm sure we have the technology to do this with electronic sensor targets today, but I don't really know where to look. It just seems logical that a 5 shot group would be a certain percentage larger than 3 shot, and a 10 shot group would be a certain percentage larger than 5 shot. Give or take a little bit.