Observations on the Points of Impact of
Statistically Significant Shot-Group Sizes

The Set-up

For this ballistic exercise I used a semi-automatic  AR-15 with a 20” stainless steel Lothar-Walther barrel.  This barrel has a 223 Wylde chamber with a 1:8” twist rate.  This Lothar-Walther barreled AR-15 has produced 10-shot groups with extreme spreads measuring in the “sixes” (0.6xx inches) when fired from the bench at a distance of 100 yards using match-grade hand-loads.  Prior to the beginning of this exercise, this barrel had approximately 2,040 rounds fired through it.

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The ammunition used for this exercise was factory loaded Black Hills red-box 223 Remington ammunition seated with the 69 grain Sierra MatchKing with a cannelure.  Since I had been testing other ammunition with the Lothar-Walther barreled AR-15 prior to the beginning of this exercise, as well as throughout this exercise, I fired three “seasoning rounds” of the Black Hills 69 grain Sierra MatchKing ammunition to condition the bore of the Lothar-Walther barrel with the powder used in this factory load.  This process was repeated immediately prior to shooting each of the groups evaluated for this exercise.

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All of the shooting for this ballistic exercise was conducted from a concrete bench-rest at a distance of 100 yards (confirmed with a laser rangefinder.) The Lothar-Walther barrel used in this exercise was free-floated in a LaRue Tactical railed free-float handguard.  The free-float handguard of the AR-15 rested in a Sinclair Windage Benchrest (with the aid of a Sinclair  forend bench-rest adaptor) while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade used. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.

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The Wind Probe.

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The Groups

No changes were made to the elevation or windage settings on the scope throughout the entire course of this exercise and the exact same point of aim was used when shooting each group.  After firing the three “seasoning rounds” of the Black Hills 69 grain Sierra MatchKing ammunition, I settled-in and fired a 20-round group of the aforementioned ammunition.  The group is pictured below.  It has an extreme spread of 0.94".  The center of the 20-round shot-group is located in the lower-right quadrant of the two inch circle on the target.  After shooting this group, I continued testing other ammunition from the same Lothar-Walther barreled AR-15.

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A little later that day, I fired a second 20-shot group of the Black Hills 69 grain Sierra MatchKing ammunition from the Lothar-Walther barreled AR-15.  The second group is pictured below and this group has an extreme spread of 0.85".

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As you can see, the center of the second 20-shot group showed no significant shift whatsoever in its location on the target as compared to the first 20-shot group.  The next image shows the first and second 20-shot groups over-layed on each other using Adobe Photoshop with the blending opacity set at 50%; further illustrating that the centers of the two 20-shot groups showed no significant shift in their locations on the targets compared to each other.

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On an additional trip to the shooting range, I repeated this entire ballistic exercise just as described above.  The findings were the same; the centers of two 20-shot groups fired from the Lothar-Walther barreled AR-15 using the same lot of Black Hills 69 grain Sierra MatchKing ammunition showed no significant shift  in their locations on the targets compared to each other.  Nor did the centers of these third and fourth 20-shot groups show any significant shift in their locations on the targets as compared to the first and second 20-shot groups fired in the previous ballistic exercise.

The graphic below shows all four of the 20-shot groups over-layed on each other (forming an 80-shot composite group) illustrating that the centers of all four of the 20-shot groups showed no significant shift in their locations on the targets compared to each other.  Of those 80 shots in the composite group, 95% of them are contained in a covering-circle that has a diameter of 0.97 MOA.  All of the 80 shots in the composite group are contained in an area-of-dispersion (bounding rectangle) that measures 1.07 MOA wide by 1.08 MOA high.

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+1

Good stuff, Molon.

It would be interesting to run this test from sea level to say 5000 feet to see the change in POA.  Just mulling...

Here in Idaho within 2 hours we can get +-800 feet to 5000 or more pretty easily, starting at Lewiston.  Not your test I know, but it would be interesting nonetheless and your test here just got me thinking.

Hey look, and ACTUAL MOA barrel

What lower is this?  I like the text.

were you expecting them to change?

Im trying to rack my mind of how you would get them to change with all the constants you had, I would guess temperature/changes in elevations (environment) being the only thing.

I don't see why the group size would change.  The point of impact might shift, but why would the group size change?

I gotta agree there, to first order, altitude should not have any impact on group size. It will certainly change POI.

Nope.

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LOL @ clown action.  Awesome.

fucking agreed, this is good information.

That's what I am referring to.  I didn't say or suggest the group size would be any different, tho I guess with air density in relation to various bullets shapes, in theory it could be.

It's Photoshopped.


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    Great shooting as always.  I imagine if a prairie dog had a nightmare you would be the villain.

thank god, I'm about to seize out trying to understand why they would


keep up the excellent work

Nothing to add, but you have been a great resource for this board. Thanks.

That is an impressive rifle/barrel/ammo combination. The shooter must be somewhat adequate also ;). These are some of my favorite threads.

Love the engraving on the right side of your receiver!

It's just a Photoshop.  But, one day I want to have a receiver engraved like that.


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+1. Been a fan of Molon for years. Glad he's back from his hiatus.

Thanks for Sharing.. Good stuff..

Love your dog, You should have him/her in at least one picture in each of your threads...

This one might get a little jealous.






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What is the point? You are an excellent shooter and you have a nice set-up. Do you mean to illustrate the variability of shots due to mechanical reasons or is it more about the human factor? I know with me it's the human factor. It's about all I can do to calm down and shoot three shots as carefully as I can - but when I do, results are good, and groups are small enough to be meaningful for scope adjustment if needed. Perhaps you could just add a sentence at the end of your articles summing up your conclusions. It would be very helpful to the AD types like me who basically skim articles like that.

I don't know if this would be helpful or not...back in the early 1990's when I was at USAFA, I had to take a probability ands stats class taught by the Math deparment.

If I am remembering correctly, we calculated Circular Error Probability (CEP).

Just now doing some googling, I found this .pdf that relates to rifle shooting and CEP:

http://www.google.com/url?sa=t&source=web&cd=8&rct=j&q=how%20to%20calculate%20circular%20error%20probable&ved=0ahUKEwikwa2Xw8LKAhXKmIMKHcECBacQFgg2MAc&url=http%3A%2F%2Fwww.statshooting.com%2Fpapers%2Fmeasuring-cep-mcmillan2008.pdf&usg=AFQjCNHNn73If3ZyqQ1LADbQsxSWmF1vxw

Maybe that would be of help to somebody.

My TL;DR: With a good rifle/ammo combo and no changes, even on different days with slightly different conditions, point of impact will remain true. If POI is significantly different, something probably went wrong or is not optimal, maybe the ammunition's load, the barrel, the sights, the weather, or that particular combination together.



Three shot groups are not statistically significant: http://www.ar15.com/forums/t_3_118/279218_.html. More rest time (or for some folks, less time to think) between shots may be required to reduce the human factor.



 

Nice summarization.

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fantastic thread Molon.  Wish we could see this for multiple barrels but I cant afford to supply you with them!

Even if you could, there wouldn't be enough hours in the week for me to test them.

And Lothar Walther didn't even give me an accuracy "guarantee."



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Da nada.


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We need an animation .gif for that.


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The red trace is at sea level, the green trace is at 8000 feet above seal level.






While the decrease in air density at the higher elevation will alter the point-of-impact, it will do so equally for all the shots, so there shouldn't be any change in the precision of the groups. (Unless you want to get into things like the few 1/100ths of an inch difference in vertical dispersion that might theoretically occur do to the few more feet per second difference in the extreme spread of the velocity at distance, at the 8000 feet above sea level, all of which would be utterly lost in the noise of the overall system.)


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Hey, thanks for that.  Really interesting.

Your graph points to something we have noted on the ranch here.  I have a rifle range at which we can shoot to 1000 yards.  Both for the specific issue at hand, and also in that it points to something I've noticed in range firing over the years. In a general sense, tho 100 yards or 100 meters is the most common distance we see tests of all sorts shot at due I suppose to the limitations many find themselves faced with on commercial ranges, 100 often appears to be simply too short a distance to highlight variations in impact, etc.  We've seen this over and over on the range here.  We like to do most of our shooting at 200 meters where variations begin to be more noticeable.  Much military testing used to be and I assume still is shot at 300 {yards in the old days, meters more recently.  Makes sense.

That's not what this thread is about, but I did enjoy the following quote from the article:

"In addition, the human tendency to report 'the best results I’ve ever gotten' as 'typical results' may lead to optimistic assessments of some configurations.  At their worst, methods using small numbers of shots and ignoring most of the information from those shots have a substantial probability of leading the shooter to choose the less accurate configuration. "

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Is it known what type of powder is used in the Black Hills ammo?

+1

Further, I would argue as I mentioned above, that shooting exclusively at 100 {y/m} is just as much of a practical handicap to really knowing what the rifle will do at extended ranges as is shooting with smaller numbers of rounds fired {5 shots, say, compared to 10}.  Just as the tendency to say "This is what I can do" is belied by small shot groups, so is shooting at one range inadequate to asserting what the rifle will do at longer range.  Thus graphs and such interpolating results at 100 are approximations of what will happen at longer range.  They are not known factors.

That 10-shot groups are superior to 5 or 3 shot groups is not to be denied, but performance at extended range cannot be accurately extrapolated merely from the results of firing at 100.  For example, the potential for the phenomenon known as compensation is not known unless the specific rifle is shot at longer ranges.  Actually SHOOTING at the range one wants to assess is important.  Some rifle/load combinations are very consistent.  Some are not.

What we KNOW from shooting at 100 is how the rifle/load shoots at 100.  

Thank you Molon for taking the time to document your hypothesis and sharing them with us.  

YOU are one of the main reasons I pay for a membership to this site.  

Why the hissy fit?

I made some accurate and truthful comments.  What's to fuss about?

BTW, the graph doesn't prove anything.  Except the numbers, which do not necessarily translate into actual range results. And that I already knew.

Calm down, Molon.  Nobody is stealing your toys or kicking you out of the sandbox.  You are among friends.

Now, get on over to the SHTF Challenge and have some fun.  

Why all your obfuscation?  

Instead of carrying-on about long range shooting in a thread that has absolutely nothing to do with long range shooting, why haven’t you actually used some of your time, your money, your equipment and your energy to conduct your own statistically significant long range testing and posted your data in a thread that actually pertains to long range shooting?


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Molon.....

Quote..."I fired three “seasoning rounds” of the Black Hills 69 grain Sierra MatchKing ammunition to condition the bore of the Lothar-Walther barrel with the powder used in this factory load. This process was repeated immediately prior to shooting each of the groups evaluated for this exercise. "

Years ago ... I read an article about which powders you shouldn't fire after another type/brand, because it would cause accuracy issues briefly for the first few rounds ( CMP or High Power type shooting ) ... your "seasoning rounds" comment got me thinking about it again.

Are you aware of such a list ?

How do the seasoning rounds actually work ? ...or is it just something that should be done ?

Your idea is a good one.  In the meantime, this is a discussion about POI and I didn't see anywhere in your OP that the discussion had to be limited to 100 yards.

For sake of clarity, so there isn't any more "obfuscation" {we wouldn't want that}, please post up a list of rules for the thread so others don't inadvertently post something that hurts your feelings.  We don't want to do that and we certainly don't want to waste time posting in a thread where we are going to find ourselves chastised merely for taking part.

How about a list of "off limits" discussion points you just can't bear to see in this thread?  That would be nice.

Thanks.

EVR.... just let it go. Snarky comments are not needed.

Molon works very hard at enlightening us, I appreciate it,  we all should appreciate it... he doesn't do it for the "Glory of the Internet".... he shares with us to help educate us.

If you don't agree with what he says... move on, it is that simple.

It is ok to disagree with people... but we are all still in this together.

I for one would like to get back to the original topic.

It is just the internet.... and a discussion about POI "when fired from the bench at a distance of 100 yards using match-grade hand-loads"


Geezzz..... Lol

OK!

There's the Rule!

Got it!!

The point is the thread was about POI at a hundred yards with DATA. If you fire enough rounds in each group, it shows no significant POI shift at 100 yards.

 


I'm sure if you go fire some groups at 200+ using similar methods and post the results it would be welcome as another data point. Instead you start making claims that 100 yards is not far enough bla bla bla. At 200 yards, there are many other variables other than the rifle and ammunition that drastically affect POI, namely gravity and wind drift. The longer a bullet is airborne, the less control the experiment has. Additionally, 100 yards is far enough to show a statistically significant shift, if it exists. All else being equal, and eliminating uncontrolled variables, if there is no measurable angular deviation at 100, there won't be at 200 either. MOA is 1/60th of a degree, which is an incredibly tiny measurement. If there is no shift at 100, there would be no measurable shift at 200, or even 1000 yards.

You might want to remove that chart, as, you know, it is off-topic.

;)

Honestly, I made no trouble here at all.  I made some {accurate} comments and Molon stated crying.

It might be best if this stuff was made a sticky that can't be posted under, as Molon has a long history of whining and fussing when anyone posts something about which he doesn't have experience or is ignorant of.

That's the last I'll post on this thread and in the future I'll avoid Molon's stuff as well.  

Seriously Molon, I won't comment on your stuff.  Have at it and all the best. Cheers.

Over and Out.

The chart addresses your earlier statement:
"100 often appears to be simply too short a distance to highlight variations in impact, etc. We've seen this over and over on the range here. We like to do most of our shooting at 200 meters where variations begin to be more noticeable. "



You posted no evidence to support what you said, whatsoever. If there is NO SHIFT at 100, unless there are ENVIRONMENTAL CONDITIONS that cause a shift (like wind), there will be no shift at 200. Your comments were NOT ACCURATE although you are portraying them  as so. They are your opinion. That is what is messing up this thread. Misinformation.