Yeti

Tightening Groups at Distance

CPAjeff

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Quick question, have any of you experienced a tighter group at 200 yards than at 100 yards with the same load?

Yesterday I hit the range to test some new loads. I shot groups at 100 and 200, fresh new targets for each group, solid rest, etc. One load was .9" at 100 center to center, and that same load at 200 was .7" center to center. Each shot felt great, and I don't believe there was a flinch/flyer . . . The other loads shot as expected ~ .75" at 100 and near double that at 200.

I loaded another batch last night and will do another round of testing later this week. I'm interested to see what happens!
 

Doublecluck

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This is pretty common. More so I think with hybrid and secant ogive bullets in fast twist rates. I will not even pay attention to vlds or hybrid groups at 100 because years ago I was using a proven load development technique and couldn’t get what should be a good load to shoot very well at 100. I was going to run it anyway, when I went to do long range drop verification it turned out it was a really really good load that just didn’t group well at 100. Here is a extreme example, 156 eol, right group was at 100, left was at 300, same day, same load, everything the same shot minutes apart.

You can also experience this phenomenon from using some high power scopes fully zoomed in at close range from parallax
 

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Rhcuam

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Brian Litz with applied ballistics had something on Facebook last week about group convergence The quick notes version is it’s a myth.

Below is from the bookface.

“These are examples of groups fired on our 100-300 yard 'shoot-thru' target. Bullets pass thru the paper at 100 yards and continue on to 300 where you see a bigger version of the same group.

This test and many others were fired on the shoot thru target, looking for something that would result in non-linear dispersion, meaning, smaller moa group at 300 than 100 as claimed by many on the internet.

Long story short, after over 70 trials, we found no evidence of non-linear dispersion. Bullets simply don't fly that way. 1 moa at 100 is 1 moa at 300.

Follow me for more ballistic myth busting⚡⚡⚡

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Rhcuam

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His follow up post as well.

To clarify something on yesterday's post about group dispersion on the 100-300 yd shoot -thru target...

Some comments connected group convergence with bullets 'going to sleep'; and since group convergence isn't real, then the idea of bullets going to sleep isn't real.

Not so fast.

It is possible for bullets to be launched with some dynamic that induces extra drag from right out of the muzzle until the bullet dampens out the pitching and yawing. However, that process does not result in group convergence. You could shoot good groups or bad groups with a launch dynamic. If it happens the same way every time, the groups will probably be good. If whatever is causing the launch dynamic is random in direction, then your groups will probably be big. But the groups will be good or bad at all ranges proportionally, not shrink as the bullet goes to sleep.

Here's an example of a 10 shot string measured with Doppler radar showing a typical launch dynamic. The plot in the lower right with the ski jump looking end is showing drag induced at the muzzle due to launch dynamic which pretty quickly dampens out (that curve usually terminates as a straight line). Also you can see that the BC measured in the first 50 yards is quite a bit lower than the BC beyond that.

That's a picture of the bullet 'going to sleep', which is real, but it's not a mechanism for group convergence.

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VikingsGuy

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Nice to have the data from Litz - but the laws of physics already require this result. An object in motion will remain in motion in that same direction unless a new outside force is applied to it. What possible force could be applied at 100-200 yds that would force a bullet to alter its course consistently back to original point of aim? There is none.

Observations like OPs are simply answered by the huge variance presented by small groups. Until the number of shots in a group exceed 30, you just have a vague estimate.
 

CPAjeff

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Yeah I was gonna ask how many shots were in your groups, and/or how many replicates. Sounds like a load that's working well for you either way.

Thanks!

Five shot groups. This is the first time I've ever experienced a tighter group at 200 than at 100, so my sample size is pretty small. I usually see the normal linear increase in group size as the yardage increases.

Either way, it seems to be plenty accurate for the distances I will be shooting!
 

Doublecluck

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I’ve read litz’s among others thoughts on this, some of which the popular opinion has changed. obviously the physics behind it. None the less it is something I have experienced for whatever reason. Here is another example, 109 Berger hybrid on top at 100 same load same day at 400 on bottom. Statistical anomaly, parallax, mirage, aliens.. whatever, it’s happened enough times over the years to notice. 746DEB38-24B0-4824-8761-F15F08ED01E3.jpeg
 

cahunter805

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Just curious. Were both groups shot from the same position?
I’ve often found that I shoot much better prone and have better recoil control vs off a bench.
 

MTTW

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I experienced the same years ago and chalked it up to parallax in the scope. This was easy because I was using a simple inexpensive scope. I solved the issue by testing at 300 yds. and not worrying about it. The set up served me very well for 30 years and then I discovered the internet and realized that I was doing it all wrong. Then things started to get expensive. :)
 

std7mag

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This is pretty common. More so I think with hybrid and secant ogive bullets in fast twist rates. I will not even pay attention to vlds or hybrid groups at 100 because years ago I was using a proven load development technique and couldn’t get what should be a good load to shoot very well at 100. I was going to run it anyway, when I went to do long range drop verification it turned out it was a really really good load that just didn’t group well at 100. Here is a extreme example, 156 eol, right group was at 100, left was at 300, same day, same load, everything the same shot minutes apart.

You can also experience this phenomenon from using some high power scopes fully zoomed in at close range.
You shot the Keurig??!!
:eek:

What kinda sadist are ya??!!
:devilish:
 
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