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I think my actual Google search term was "What's the significance of the three-shot group?" Within the first few search results was this post: http://www.bealeinnovations.com/stats-3shotgroup.pdf

Now, I admit that I'm not a statistician/mathematician/engineer; however, other than kind of losing me with his three dimensional graphs, everything else he wrote about actual shot distribution seemed to make sense. And, I agree with his grandpa - hitting what you're shooting at is the point.

So, with that in mind, I ran my most recent 10-shot targets back through the OnTarget app to display the mean radius circle (drawn using the average distance of all the shots from the center of the group) and the group extent box (created by drawing intersecting straight lines through the center of the most outlying shots).

The rifle is a PTR 91 GI Classic; the ammunition is MEN 16 7.62x51. Unless otherwise noted, all the targets were shot from a table rest with the iron sights.







When shooting this target I was sitting on a small block and resting the barrel on a rail.


When shooting this target I was standing and using the sling.




When shooting this target I was standing, but leaning over and resting my elbow on a shelf.
 

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I kind of skimmed it, but it seems he generally has the right idea, as far as he goes. Basically what he's saying is that, if you only shoot three rounds, it's possible through simple luck that they would land close to each other and near the point of aim, meaning that you think your grouping and sight adjustment are good when they're really not. If you shoot ten rounds, there's a much smaller chance of that happening.

One thing he doesn't take into account, though, is assignable cause variation. In shooting that's called fliers. If you're really getting statistical about it, you have to shoot a lot more than ten rounds, calculate the standard deviation and control limits, and eliminate any shots that are out of control (meaning something caused the result besides random variation). Most people do this intuitively; if they have nine shots in a 1" group, and one shot 3" away from the rest, they know something went wrong with that one and ignore it.
 
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I kind of skimmed it, but it seems he generally has the right idea, as far as he goes. Basically what he's saying is that, if you only shoot three rounds, it's possible through simple luck that they would land close to each other and near the point of aim, meaning that you think your grouping and sight adjustment are good when they're really not. If you shoot ten rounds, there's a much smaller chance of that happening.

One thing he doesn't take into account, though, is assignable cause variation. In shooting that's called fliers. If you're really getting statistical about it, you have to shoot a lot more than ten rounds, calculate the standard deviation and control limits, and eliminate any shots that are out of control (meaning something caused the result besides random variation). Most people do this intuitively; if they have nine shots in a 1" group, and one shot 3" away from the rest, they know something went wrong with that one and ignore it.
Unless it's a hunting rifle and it's always the first shot that does that, when the barrel is cold. Then it's best not to ignore that.
 

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You'll hear all manner of theories on number of rounds needed. Just like the old saw between how to break in a barrel, is it fire one and clean for 10 and continue to 5 rounds and clean or do you continue to 10 rds and clean.
 

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Three round groups work for me. If I throw a flier, I'll shoot one more.
 
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At no point does the author address barrel heating or cooling. Besides other bench shooting variables, that is the most glaring error in my book.

To save ammo, shoot 3, adjust, shoot 3, verify. That is hunting accurate. Low round count, plus walking the range lets the barrel stay cool.

From there, if you really want to shoot X's, you need to start adjusting handloads to find out what weight bullet and velocity your rifle shoots best. We haven't even mentioned wind yet. Shooting accurately takes a long time.
 

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Shooting accurately takes a long time.

Nah, boot comprised 1 week of field position snap in and one week to qualify, and that was with irons out to 500 yrds. It's not the time, it's the motivation and instruction that determines the length of time necessary.

Counter sniper school was 5 days, qualification on the 5th day [ though not shot past 300 yrds, and then just once as most urban snipers shots fall in the range of 77 yrds ]. And you best be able to thread the needle on demand to get the certification which is based on a national standards test.
 

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Discussion Starter · #9 ·
I kind of skimmed it.... One thing he doesn't take into account, though, is assignable cause variation. In shooting that's called fliers.
Actually, I think he acknowledges it in his Disclaimer toward the bottom of the first page.
 
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Shooting accurately takes a long time.

Nah, boot comprised 1 week of field position snap in and one week to qualify, and that was with irons out to 500 yrds. It's not the time, it's the motivation and instruction that determines the length of time necessary.

Counter sniper school was 5 days, qualification on the 5th day [ though not shot past 300 yrds, and then just once as most urban snipers shots fall in the range of 77 yrds ]. And you best be able to thread the needle on demand to get the certification which is based on a national standards test.
Thread the needle...
I that where you shoot the arrow through like a dozen battle axes?
:wink:
 

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Honestly it just depends. When I am handload ingredients for the upmost accuracy I shot three shot groups. I also let the barrel cool at least 5 minutes between each trigger pull.
If I'm just playing around I may shoot a 10 shot group in under a minute.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 

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When working up a load for any of my rifles I shoot 5 shot groups, once I find the one that works I'll shoot a 10 round group. I then go out in 100 yard increments.
 

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Good answer, H. It depends.
I didn't click the link, but in replying to the thread topic, I believe it only takes ten shots if you are a bad shot or your rifle isn't known for its accuracy. Otherwise you should know where it's hitting after a couple shots.

Of course if you are going to keep shooting it even though it's not hitting where you are aiming, or where you expect it should be hitting, that's a different topic.
 

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When working up a load for any of my rifles I shoot 5 shot groups, once I find the one that works I'll shoot a 10 round group. I then go out in 100 yard increments.
This is obviously fine tuning.
I didn't want my previous post to mean you should never shoot ten round groups.
 

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Not if they make one hole or cloverleaf.
 

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I know why I use 3 shot groups. Any more than that and my skinny barreled hunting rifles start to heat up and move! after I have gotten the sights about dialed in Ill shoot one and set the gun aside for 30 min to see that my first shot is on target. Because that's the one that counts! DR
 

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The worst thing about shooting a five shot group is when the first three are in the same hole.
Those next two shots are brutal.
You're almost better off shooting a cluster.
 

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More reading material on the subject: Understanding Rifle Precision - The Truth About Guns

And some practical interpretations: 5 Shot Groups VS 10 Shot Groups - RimfireCentral.com Forums

And lastly, my own observation from punching a lot of paper with scoped rimfires over the past few years: the actual target you use, as well as the type of aiming device, can affect the spread of your shots. If you're shooting for group size and using a scope, a crosshair target will give you more consistent results than even a small bullseye. Serious paper punchers will deliberately offset the POI from the center of the crosshair so as not to shoot out their aiming point. If shooting with irons, a target that affords you good contrast and the smallest aiming point you can resolve at any given distance will give you the greatest consistency - "aim small, miss small." Just a suggestion - if you're putting in the effort to analyze your targets with On Target (which I do often, as a numbers guy), you deserve to take some more variability out of the experiment. I use adhesive fluorescent-colored circles on my targets at times to give me a good, repeatable aiming point.
 

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Sometimes when I shoot my deer rifle before opening day to make sure it's still on, I might be quite satisfied with a one shot group if it hits the same as it did last season.
 
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