Do we care more about, SD or ES?

[Golfnut721]

When choosing an ammo for competition (not practice), what would you focus more on? I tend to lean more towards ES over 100 shots, mostly because in a standard COF at an X match or PRS match your going to shoot 100-110 rounds. If my SD is low but my ES is what i would call high I'm assuming there are going to be a couple rounds out of that 100 that are going to be way off target. I could be wrong but just my thinking.

Thoughts?

 

[DIBBS]

BOTH, they are directly related to one another.

You want your ammunition as consistent as possible, with as little variation as possible within reason.

You can't control this with factory ammo, but a number of folks have good luck in PRS competitions shooting factory ammo.

Long Range Shooting: Understanding Extreme Spread And Standard Deviation - Guns and Ammo

With the increase in interest in long-range shooting, the terms extreme spread (ES) and standard deviation (SD) are being thrown around a lot.

www.gunsandammo.com

 

[justin amateur]

If you simplify the calculations, standard deviation is what to expect for 2 out of 3 shots.
That works out to 34 shots from a box of 50.
SD ignores the other 16 shots from the box.
I want to know what to expect from the full box of 50.
That's why Extreme Spread is the number I care about.
If the ES is over 40 fps, it's not good enough for bench rest at 100 yards.

 

[Hecouldgoalltheway]

There is a very successful benchrest or F class shooter that is known by "speedy gonzales". He apparently owns more than his share of records in those disciplines. He did a podcast interview a few years ago with Eric Cortina and he said that neither matter one bit. He only cares where the bullets impact the target. He claimed to have loads with crazy es and SD, and had won world championships with them because they stacked on target, and that those things didn't matter. This is a guy who weight sorts primers and other silly shit for precision, and he said to stop worrying about either es or SD.

Not my words, but given the source, it's an interesting claim.

 

[grauhanen]

It's not helpful to think of only one or the other. ES shows only two things, the fastest and slowest MVs of a sample. It doesn't show anything at all about the other 48 rounds in a box. SD shows how alike the rounds are with regard to MV. A small SD means they are closer to each other in MV; a larger MV means that they are less close to each other in MV.

A key problem with ES or SD is that, even discounting wind, neither determine where on a target the bullet will impact, unless you subscribe to the false belief that MV determines POI. It doesn't -- as anyone who's tracked MV/POI can confirm. Some bullets with faster MVs can strike lower than slower ones and vise versa. There's more to POI than MV alone.

 

[BuildingConceptsllc]

Well you aren't going to get any real numbers for ES because you won't shoot enough rounds to find out. So.... get 20 shots and your SD, then you can extrapolate your ES from that SD. This is really the only practical way to do it. With a 20 shot SD, you can get pretty good confidence level of your ammo and ES. All of this other stuff is just picking numbers which you have no idea if it's legit or not and many on here have no idea what they are talking about concerning these things frankly.

 

[Jefe's Dope]

neither determine where on a target the bullet will impact, unless you subscribe to the false belief that MV determines POI. It doesn't -- as anyone who's tracked MV/POI can confirm. Some bullets with faster MVs can strike lower than slower ones and vise versa. There's more to POI than MV alone.

Then why enter a MV in your ballistics calculator. Or use a ballistics calculator at all?

 

[justin amateur]

Does muzzle velocity affect trajectories? Yes.
Differences in time of flight changes the amount of time gravity pulls down on the projectile.
Those time differences affect the vertical location of the point of impact.
Is muzzle velocity the only factor that affects vertical spread? No.
Wind, barrel harmonics, bullet symmetry/balance and heel damage
can cause vertical spread also, either added to or subtracting from that caused by gravity.
Muzzle velocity differences always cause vertical spread, but can be hidden by the other factors.


The basics of standard deviation calculation....

Standard Deviation and Variance

From a box of 50, the number of cartridges that fall within the SD is 34.
That tells you that 16 cartridges will fall outside the SD from that box.
Is that something that will affect your decision when buying ammo for an ARA or USBR target?

 

[grauhanen]

Then why enter a MV in your ballistics calculator. Or use a ballistics calculator at all?

For those who use a ballistics calculator to help prepare for shots at long or varying distances, when using the same kinds of bullets that weigh the same nominal 40 grains there's not much else ammo-related to enter.

Ballistics calculators predict what should happen when using bullets that are perfectly symmetrical and balanced. The trouble is that soft lead projectiles such as .22LR match bullets (and airgun pellets) are rarely perfect that way. The problem is because, unlike jacketed bullets, it's very difficult to make perfectly symmetrical and balanced soft lead bullets. It's virtually impossible for shooters to measure or sort for symmetry and balance. When bullet characteristics are less than ideal, no ballistics calculator will be accurate with regard to MV/POI predictions.

Some lots are better or worse than others in terms of bullet symmetry and balance. That's why some lots of the same variety of ammo are better than others. In fact, in the same box some bullets in a box may be better or worse than others.

To add to the issue, bullets are obturated uniquely by each rifle's chamber/leade and bore. That obturation also affects bullet symmetry and balance. It helps explain why some rifles/barrels do better at longer distances than others, even though they may all shoot well at, say, 50.

 

[Hi-NV Shooter]

Does muzzle velocity affect trajectories? Yes.
Differences in time of flight changes the amount of time gravity pulls down on the projectile.
Those time differences affect the vertical location of the point of impact.
Is muzzle velocity the only factor that affects vertical spread? No.
Wind, barrel harmonics, bullet symmetry/balance and heel damage
can cause vertical spread also, either added to or subtracting from that caused by gravity.
Muzzle velocity differences always cause vertical spread, but can be hidden by the other factors.


The basics of standard deviation calculation....

Standard Deviation and Variance

From a box of 50, the number of cartridges that fall within the SD is 34.
That tells you that 16 cartridges will fall outside the SD from that box.
Is that something that will affect your decision when buying ammo for an ARA or USBR target?

IDK, maybe bullet barrel time will affect POI? like where the barrel is pointing when the bullets exit? since all barrels start off down and not pointing up. if higher velocity means the bullet exits earlier from the barrel where is the barrel pointing?

Lee

 

[justin amateur]

I agree with ya' Lee, barrel dwell time can make a difference.
I had a pencil barrel savage, barrel whip would sling strays all over creation.
The more energy involved, the greater the spread in all sorts of directions.
I figure that is covered as extreme barrel harmonics.

 

[Mike Islander]

Isn't 100 fps change only about 0.1 inch different POI, all else remaining the same? Doesn't seem to matter.

 

[justin amateur]

At 25 yards it's not a worry Mike.
At 50 yards or more, 100 fps difference is a problem.
Break out y'er calculator and run the numbers.

 

[Milo 2.5]

Isn't 100 fps change only about 0.1 inch different POI, all else remaining the same? Doesn't seem to matter.

At what distance are you referring to? We can only try simplify things so much.

 

[Milo 2.5]

I tend to not chrono a lot of 22LR ammo. If it shoots well at the distances I expect it to, I chrono for ballistic solvers.
I always ask myself what am I prepared to do or how far will I take it if hit percentages aren't over a certain number. Right now, it is not like good or great ammo is falling from the sky.

 

[lash]

Isn't 100 fps change only about 0.1 inch different POI, all else remaining the same? Doesn't seem to matter.

Uhm Mike, we are in the rimfire section. The difference between impacts at 100 yards with a total of 200 fps is 0.8 mils or about 4.5”. Half of that is still over 2” variation in POI at 100 yards with a 50 yard zero.

ETA: unless of course that was sarcasm, in which case…good one!

 

[Csafisher]

There is a very successful benchrest or F class shooter that is known by "speedy gonzales". He apparently owns more than his share of records in those disciplines. He did a podcast interview a few years ago with Eric Cortina and he said that neither matter one bit. He only cares where the bullets impact the target. He claimed to have loads with crazy es and SD, and had won world championships with them because they stacked on target, and that those things didn't matter. This is a guy who weight sorts primers and other silly shit for precision, and he said to stop worrying about either es or SD.

Not my words, but given the source, it's an interesting claim.

Being that he is a centerfire benchrest shooter, this is completely out of context compared to rimfire.

 

[Hecouldgoalltheway]

Being that he is a centerfire benchrest shooter, this is completely out of context compared to rimfire.

I disagree. Why would that be out of context? It's still a method of measuring a projectile on flight and its effect on repeatability. The mechanics are identical.

He's not a basketball player.

 

[acudaowner]

I care more about if I can get it to group and am I hitting the target where I want to hit it . I had really piss poor sd groups that grouped for me really nice but still had really bad numbers .

 

[Csafisher]

I disagree. Why would that be out of context? It's still a method of measuring a projectile on flight and its effect on repeatability. The mechanics are identical.

He's not a basketball player.

No they aren’t. The BC is a fraction of what bullet they are shooting and the speed is obviously much slower. They also get to “tune” loads via powder charge and seating depth etc. You can’t do any of that with a 22. Shooting an SD of 15 at 100yds with a 22 is much different than shooting a 6ppc at 100yd with an SD of 15.

 

[Hecouldgoalltheway]

No they aren’t. The BC is a fraction of what bullet they are shooting and the speed is obviously much slower. They also get to “tune” loads via powder charge and seating depth etc. You can’t do any of that with a 22. Shooting an SD of 15 at 100yds with a 22 is much different than shooting a 6ppc at 100yd with an SD of 15.

To what degree SD and ES are relevant to repeatability, (which is the point I made), there is no difference..

You're arguing about how an individual can or cannot effect those things. That's a different argument. The idea that they don't necessarily equate to repeatable accuracy could apply to any projectile. You've created a strawman arguement.

 

[Csafisher]

To what degree SD and ES are relevant to repeatability, (which is the point I made), there is no difference..

You're arguing about how an individual can or cannot effect those things. That's a different argument. The idea that they don't necessarily equate to repeatable accuracy could apply to any projectile. You've created a strawman arguement.

No I’m not. I’m saying it’s apples to oranges. And it’s amplified by the slower muzzle velocity.

 

[Mike Islander]

Uhm Mike, we are in the rimfire section. The difference between impacts at 100 yards with a total of 200 fps is 0.8 mils or about 4.5”. Half of that is still over 2” variation in POI at 100 yards with a 50 yard zero.

ETA: unless of course that was sarcasm, in which case…good one!

Sorry folks. Totally my bad. Rule to self; no more PBC (posting before coffee),

 

[Hecouldgoalltheway]

No I’m not. I’m saying it’s apples to oranges. And it’s amplified by the slower muzzle velocity.

Now we are in the weeds.

I'll make it even simpler:

If you throw 10 nearly identical rocks repeatedly at the same exact target, a throwing arm velocity difference of .3% may not necessarily equal a shift in poi.

You're making a strawman arguement. This concept doesn't care about what the ignition source is.

It's simple enough to prove it too. Have you ever seen a load with good es and SD, but groups like trash? It's a thing.

 

[ma smith]

You typically want a 95% chance the true probability of your ammo <1MOA

IE, that the TRUE stochastic dispersion is constrained to be < 1MOA for >95/100 shots

Go figure that out and you are good to go.

Neither ES nor SD tell you that directly.

 

[justin amateur]

I use ES as an indicator of cartridge quality.
My ballistic chronograph is out front most bench sessions.
Numbers are recorded in sets of 50 for comparison to target results.
I've found that if the ES is less than 30 fps,
then the quality control at the factory was very good,
and results on target usually exceed my expectations.
Unless I'm dealing with turbulence and tailwinds.
ES of 40 fps and rarely am I surprised by outliers/strays.
Cartridges capable of an ES of 40 fps or less are from the better lots of 22lr.
Assembly and components have been done right.
ES of 50 fps and above, not only does vertical spread become annoying
but the reasons for the larger ES become recognizable.
Assembly and component issues start showing up as random impacts
that don't relate to wind directions or mv differences.
The greater the ES the worse the quality control and when you hit 70 fps ES and higher
y'er in the possession of 22lr cartridges with manufacturing problems,
intended for hunting and plinking, not precision.

 

[lash]

Now we are in the weeds.

I'll make it even simpler:

If you throw 10 nearly identical rocks repeatedly at the same exact target, a throwing arm velocity difference of .3% may not necessarily equal a shift in poi.

You're making a strawman arguement. This concept doesn't care about what the ignition source is.

It's simple enough to prove it too. Have you ever seen a load with good es and SD, but groups like trash? It's a thing.

Show me a single instance of that in rimfire. Just one.

You don’t get that there is a difference between CF and rimfire? Or are you just trolling because you can? Either way your argument does not apply.

Or prove it, with rimfire ammo. I’ll wait.

 

[Csafisher]

Now we are in the weeds.

I'll make it even simpler:

If you throw 10 nearly identical rocks repeatedly at the same exact target, a throwing arm velocity difference of .3% may not necessarily equal a shift in poi.

You're making a strawman arguement. This concept doesn't care about what the ignition source is.

It's simple enough to prove it too. Have you ever seen a load with good es and SD, but groups like trash? It's a thing.

Not at distance…. No I haven’t.

 

[Hecouldgoalltheway]

Show me a single instance of that in rimfire. Just one.

You don’t get that there is a difference between CF and rimfire? Or are you just trolling because you can? Either way your argument does not apply.

Or prove it, with rimfire ammo. I’ll wait.

So for you, es and SD equal accuracy and that's it.

Well shit, let me save you some time. Next time you want to test a cartridge, hook up your chrono and go shoot 50 rounds into the dirt. If the numbers are good, you're good. Zero and head to the match.

I'll bet you won't. You know you're full of shit.

 

[MarkCZ]

I tend to not chrono a lot of 22LR ammo. If it shoots well at the distances I expect it to, I chrono for ballistic solvers.
I always ask myself what am I prepared to do or how far will I take it if hit percentages aren't over a certain number. Right now, it is not like good or great ammo is falling from the sky.

I know this will start a fire storm. I have not used a chrono in years. I used one for pistols when I shot USPSA for the power factor of match loads. and in long range centerfire, working up loads getting the ES for long range benchrest.

For rimfire I don't use one. I start with the factory MV and start shooting. I true velocity and BC on my ballistic app to match what the targets are telling me out to 400yds. It does not matter what the ES and SD is. the targets will tell you. Even if you chrono, you still have to shoot on the targets. I shoot with a group of guys once or twice a week, on long range steel. Most of the time we shoot 200yds and out. We can see what the vertical spread is for each ammo on the targets or the berm. We can see xyz ammo is running 0.5 mils vertical at 200 yds. by just shooting it.

Long range rimfire is all about getting the ammo with the best vertical you can get and reading the wind. a 22 lr can change so much from morning to afternoon, much less from day to day. I have seen as much as 0.5 mils difference as it gets hotter in one day. We check the weather conditions many times a day and update ballistic app.

 

[kthomas]

There is a very successful benchrest or F class shooter that is known by "speedy gonzales". He apparently owns more than his share of records in those disciplines. He did a podcast interview a few years ago with Eric Cortina and he said that neither matter one bit. He only cares where the bullets impact the target. He claimed to have loads with crazy es and SD, and had won world championships with them because they stacked on target, and that those things didn't matter. This is a guy who weight sorts primers and other silly shit for precision, and he said to stop worrying about either es or SD.

Not my words, but given the source, it's an interesting claim.

If you are only shooting at one set distance, then I can give Speedy a pass.

But if you are shooting targets at multiple distances, ES/SD matters.

There are too many variables in shooting and ballistics, why add another with large ES/SD if you can control it?

 

[MarkCZ]

When choosing an ammo for competition (not practice), what would you focus more on? I tend to lean more towards ES over 100 shots, mostly because in a standard COF at an X match or PRS match your going to shoot 100-110 rounds. If my SD is low but my ES is what i would call high I'm assuming there are going to be a couple rounds out of that 100 that are going to be way off target. I could be wrong but just my thinking.

Thoughts?

your thinking is correct. Are you shoot these rounds at targets with the chrono or just shooting across the chrono. see my other post on this post.

 

[Csafisher]

So for you, es and SD equal accuracy and that's it.

Well shit, let me save you some time. Next time you want to test a cartridge, hook up your chrono and go shoot 50 rounds into the dirt. If the numbers are good, you're good. Zero and head to the match.

I'll bet you won't. You know you're full of shit.

No lol. I never said that.

 

[Rio Precision Gunworks]

If you simplify the calculations, standard deviation is what to expect for 2 out of 3 shots.
That works out to 34 shots from a box of 50.
SD ignores the other 16 shots from the box.
I want to know what to expect from the full box of 50.
That's why Extreme Spread is the number I care about.
If the ES is over 40 fps, it's not good enough for bench rest at 100 yards.

This is NOT how SD works. You're only using a single standard deviation with your 2/3 shots.

68% of shots will be +/- 1sd
95% of shots with be +/- 2sd
99.7% of shots will be +/- 3sd

SD takes every single shot into account. I'm not sure where you even got the idea that SD "ignores" anything. Definitely not from any class or book definition.


To the OP, google extreme spread. You'll find that magically, only the shooting community uses ES. No other literally anyone uses it. It's a worthless stat overall except to weed out something that absolutely won't work.

The above poster I quoted can use it to make preliminary weed outs of anything over 40es. But using his definition of SD, he's not even remotely using it properly and relying on an inferior statistic (ES).



The ironic part isn't just how wrong this is, but that you're actually using two single data points to make decisions when claiming that 2/3 isn't enough......

This might possibly be the worst explanation of standard deviation I've read yet.

 

[Rio Precision Gunworks]

Here's an example of how Standard Deviation actually works for anyone interested:

Say you run 10 shots over your chrono and get an sd of 7.

You'll want to run a confidence interval (typically 95%). This will give you a range that your SD is likely in (95%).

That would mean with a 10 shot string of a 7sd:

5fps - 13fps. Meaning your true SD is somewhere in there.

Which, means your ES for 95% of your shots is somewhere between:

20fps - 52fps

The other roughly 5% of your shots will be up to 30 - 78 fps



There's no "ignores 1/3"....that's just someone who only has a partial understanding. That's literally how the statistic works. We don't get to make up our own versions or viewpoints. SD is SD is SD. Period.


Now, if you decide you want 95% of your shots to be under 30es (which basically means your ammo has to have a true to life SD of 5), then yes, you can eliminate lots of ammo that have an ES over 30. But, that's where it stops.

When you see a shot string with an ES under 30 (if that's your goal), unless you run a confidence interval on your SD and find that you're either assuredly at 5fps or less.....or very, very close to 5sd or less.....you cannot confidently say that your ammo is sub 30es.

 

[Rio Precision Gunworks]

I hate making "absolute" statements. But here are a couple:

If someone isn't familiar with confidence intervals, they don't understand standard deviation.

If someone doesn't think all shots are accounted for, they don't understand standard deviation.

If someone thinks extreme spread is even remotely close to as important as standard deviation (again, you can use ES to eliminate some things), they don't understand standard deviation.



If any of those things are present in a conversation about standard deviation or extreme spread......no matter how good a shooter, how much they shoot......etc.....they do not have a firm grasp on the concepts of these two statistics. Take their advice on all the other shooting relating things, but find someone else or take a class to learn more about how to use the numbers your chronograph uses.

 

[justin amateur]

Yes, it's true, I'm guilty of oversimplifying standard deviation.
Most never apply any statistics to their chrony numbers.
They state the numbers as displayed from the chronograph as data
with no interest in further analysis. Rarely do they include the actual sample size.

I want to know the high and low velocities from each box of 50.
They are the numbers that allow me to check actual vertical spread on target
against what the calculator determines it should be.
If I get a high or low impact on target, I can check the chrony display
to confirm if it was a hot or weak cartridge to blame.

 

[grauhanen]

ES is not a reliable indicator of ammo quality. It can't guarantee results. It may not be helpful to predict results.

After tracking MV vs POI for hundreds of ten-shot groups at 100 yards, it's clear that the relationship between the two is not consistent. The inconsistent relationship happens frequently. It is no longer a surprise. It's expected.

How frequently it occurs depends on lot quality. I've tested six different lots of M+ as well as three of CX. None were immune from the MV vs POI inconsistency problem. Some boxes from every lot were better than others, but no box was immune.

I'm going to show some examples. These illustrate the problem and are not unique. The last example was shot only yesterday.

Below is one example of many that could be given. Nine shots were close together with an MV spread from 1030 to 1069 fps, an ES of 39 fps. The lone "flyer" had an MV of 1040 fps.




Below, an example with less consistent ammo, SK RM, shows how a ten-shot ES typically affects results with three of the four groups. The group on the top right is very unusual and defies expectations based on ES alone.



Below a more recent example. It shows that rounds don't strike consistently in terms of MV vs POI. In fact, sometimes slower rounds have a higher POI than faster ones and faster rounds a lower POI than slower ones.

 

[Hecouldgoalltheway]

ES is not a reliable indicator of ammo quality. It can't guarantee results. It may not be helpful to predict results.

After tracking MV vs POI for hundreds of ten-shot groups at 100 yards, it's clear that the relationship between the two is not consistent. The inconsistent relationship happens frequently. It is no longer a surprise. It's expected.

How frequently it occurs depends on lot quality. I've tested six different lots of M+ as well as three of CX. None were immune from the MV vs POI inconsistency problem. Some boxes from every lot were better than others, but no box was immune.

I'm going to show some examples. These illustrate the problem and are not unique. The last example was shot only yesterday.

Below is one example of many that could be given. Nine shots were close together with an MV spread from 1030 to 1069 fps, an ES of 39 fps. The lone "flyer" had an MV of 1040 fps.




Below, an example with less consistent ammo, SK RM, shows how a ten-shot ES typically affects results with three of the four groups. The group on the top right is very unusual and defies expectations based on ES alone.



Below a more recent example. It shows that rounds don't strike consistently in terms of MV vs POI. In fact, sometimes slower rounds have a higher POI than faster ones and faster rounds a lower POI than slower ones.

Get out of here with your scientific approach sir, there are people in this thread that are certain what your testing clearly proves is wrong. I'll bet they won't have much to say after looking at this. Besides, they've told me all day that es and SD are infallible predictors of accuracy in a rimfire.

Oh bother.

 

[lash]

So for you, es and SD equal accuracy and that's it.

Well shit, let me save you some time. Next time you want to test a cartridge, hook up your chrono and go shoot 50 rounds into the dirt. If the numbers are good, you're good. Zero and head to the match.

I'll bet you won't. You know you're full of shit.

Let’s look at this, shall we? You didn’t answer one single thing I asked. Then you changed the subject by putting worlds in my mouth and told me that the words you said were full of shit. Does that cover it?

I’m still waiting for the answers I know that you won’t provide because you’re too far down a rabbit hole that you actually don’t know anything about.

I’m waiting.

Long range rimfire is all about getting the ammo with the best vertical you can get and reading the wind. a 22 lr can change so much from morning to afternoon, much less from day to day. I have seen as much as 0.5 mils difference as it gets hotter in one day. We check the weather conditions many times a day and update ballistic app.

Yup. It’s that simple.

 

[Hecouldgoalltheway]

Let’s look at this, shall we? You didn’t answer one single thing I asked. Then you changed the subject by putting worlds in my mouth and told me that the words you said were full of shit. Does that cover it?

I’m still waiting for the answers I know that you won’t provide because you’re too far down a rabbit hole that you actually don’t know anything about.

I’m waiting.

Yup. It’s that simple.

What question did you ask?

You said that the theory that es and SD numbers don't directly equal repeatability don't apply to rimfire. That's what you claimed. You either don't understand the simplest principles of physics or you just want to argue. I've explained the irrelevance of the ignition source, or the lack of end user ability to adjust or tune ammo (as was mentioned here) to the application of said theory.

You said:

"Show me a single instance of that in rimfire. Just one.

You don’t get that there is a difference between CF and rimfire? Or are you just trolling because you can? Either way your argument does not apply.

Or prove it, with rimfire ammo. I’ll wait."

While you were waiting, @grauhanen showed up with an abundance of proof. He literally dropped an atomic bomb of evidence on your bullshit. Now you want to demand that I answer some unclear question? You look like a dipshit here. All of this because I mentioned a claim made by a hall of fame shooter. You tried to make it personal and now you just look silly.

 

[chillywig]

I have a new barrel and been getting some rounds though it and testing various types of ammo I have on hand. I have gone back to the show me your 0.0xx thread a few times. While I have shot some very good groups, often times over a chrono to help explain the bad groups I am not sure I can hold a reticle at the 0.0xx. I have been to lapua test center and had guns tested out of their vise. I would assume they can hold the gun in the fixture with 0.0xx scope movement. But never seen 0.0xx groups out of any of my guns at the test center. I mean how accurate and repeatable should we expect a 22lr to be with the potato BC/bullet shape we are working with?

 

[grauhanen]

I have been to lapua test center and had guns tested out of their vise. I would assume they can hold the gun in the fixture with 0.0xx scope movement. But never seen 0.0xx groups out of any of my guns at the test center. I mean how accurate and repeatable should we expect a 22lr to be with the potato BC/bullet shape we are working with?

It's not so much the "potato" (?) bullet shape or its BC that prevents many shooters from seeing repeatable 0.0xx groups at the testing center or elsewhere. Two things must always be kept in mind. One is that not all rifles/barrels can shoot so well, regardless of ammo. The other is that not all ammo can shoot so well, regardless of rifle/barrel (or if it's in a vise).

Even if a superlative barrel is used (whether in a vise or not), the nature of the ammo makes repeatable 0.0xx groups infrequent. The problem is that it's difficult for match ammo makers to make ammo that's extremely consistent -- and this means not only in small ES and SD figures. Key requirements in addition to small ES and SD include cartridges with bullets that are close to being perfectly symmetrical and balanced, consistently seated, and very consistently crimped in the case. Lots with such ammo exist, but they are few and far between.

For an example of what rifle/barrel and ammo excellence looked like less than ten years ago, see this 2014 record https://bulletin.accurateshooter.co...-shots-at-50m-new-record-at-eley-test-center/

 

[chillywig]

For an example of what rifle/barrel and ammo excellence looked like less than ten years ago, see this 2014 record https://bulletin.accurateshooter.co...-shots-at-50m-new-record-at-eley-test-center/

Be interesting to see the ES SD numbers for these groups. I have only been to OH lapua test center 2 times. Both trips the chrono was not working

 

[grauhanen]

Be interesting to see the ES SD numbers for these groups. I have only been to OH lapua test center 2 times. Both trips the chrono was not working

Since there's considerable misapprehension and misinformation about chronograph results, it may not be a surprise if remedying the lack of chronograph data is not a priority. What's ultimately important is the results on the electronic target regardless of what the chrony might show.

With regard to the ES and SD numbers for the groups shown in the link, suffice it to say that the ammo used was good, with a small ES and SD.

In a small sample size such as ten rounds in a group, ES and SD figures aren't very meaningful. In any box of ammo there are bound to be smaller and larger ES and SD figures for random groups of ten rounds. What might be more interesting is the ES and SD for an entire box of ammo rather than for ten round groups.

Even in a box of ammo with a larger ES, smaller sets of samples (e.g. ten rounds for a group) will typically have a much smaller ES. It's only by chance that any one set of ten rounds will have both the fastest and slowest rounds from the whole box of ammo. When SD numbers are small, it's likely to have sets of ten rounds that will be close to alike in MV.

When shooting at 55 yards (very nearly 50 meters which was the distance in the link) bullets that are not compromised by asymmetry or imbalance -- that is, ideal bullets -- will be likely to have trajectories as predicted by ballistics calculators. Ten rounds within a 10 fps ES will have vertical dispersion of about 0.08". Ten rounds with a 5 fps ES will have about 0.04" of vertical.

 

[epeet]

Both tell you something about the ammo, and can help you decide on a lot number. Both are really helpful in understanding why cheap ammo is cheap...

 

[ma smith]

In a small sample size such as ten rounds in a group, ES and SD figures aren't very meaningful.

Taken individually, you might be correct. The whole point is to use them together.

We use ES because SD is unreliable when N=Small.
We use SD because ES is unreliable when N=Large.

The reason we don't use just one or the other is (generally speaking) getting N=large data sets is HARD.
The reason that the data is hard, is probably another discussion...

But its all critical to "what we care about" when talking ammo quality, whether its testing factory or load dev.

Just my $0.02c

 

[chevy_man]

For rimfire, they both matter.

Lot test, and buy what shoots. It will generally have low SD and a fairly low ES with the occasional true extreme.


Center-fire is a whole different animal. I tune my loads looking for SD under 10 and ES under 20 across 100 rounds.

 

[lash]

Don’t you guys get it? A shit ton of irrelevant data and two shit tons of words are telling you that external ballistics don’t matter…unless they do and then the argument is reversed.

What a buncha dough heads. Believing in actual relevant data and feedback from shooting actual .22 ammo. Phhhfftt! Fudds!

 

[Hi-NV Shooter]

It's not so much the "potato" (?) bullet shape or its BC that prevents many shooters from seeing repeatable 0.0xx groups at the testing center or elsewhere. Two things must always be kept in mind. One is that not all rifles/barrels can shoot so well, regardless of ammo. The other is that not all ammo can shoot so well, regardless of rifle/barrel (or if it's in a vise).

Even if a superlative barrel is used (whether in a vise or not), the nature of the ammo makes repeatable 0.0xx groups infrequent. The problem is that it's difficult for match ammo makers to make ammo that's extremely consistent -- and this means not only in small ES and SD figures. Key requirements in addition to small ES and SD include cartridges with bullets that are close to being perfectly symmetrical and balanced, consistently seated, and very consistently crimped in the case. Lots with such ammo exist, but they are few and far between.

For an example of what rifle/barrel and ammo excellence looked like less than ten years ago, see this 2014 record https://bulletin.accurateshooter.co...-shots-at-50m-new-record-at-eley-test-center/

I don't put much precedence on composite groups. IMO they really don't show a true meaning of how the rifle shot the ammo.
otherwise, these groups if compiled together would be very impressive especially since they were shot outdoors not in a tunnel and off a rest.
the first target 25 shot composite group of 7.79mm next 30 shot composite group of 8.128mm this group is including the fouler from a fresh clean bore and last targets 50-shot composite group of 13.76mm.
I will rely on actual multi-shot groups such as this 20-shot group which is 10.49mm by the way the group was shot with CX 1117 same lot as this 5-shot group on the top so based off this 5 shot group not surprising it shot the 20-shot group.

now what was the SD /ES? I don't care if the ammo will shoot like this does it matter?

Lee