Home Forums Hunting & Shooting Ask The Gunwriters SD and ES

Been doing more reading on SD and ES in a load and why you want them to be low. Makes sense.

I'm wondering what you all consider to be "low" for this number? That is - if a guy gets to 10, consider that good or is good actually 7 and great 5 - so to speak.

Where do you like to be? Is there a floor where you'll just never get under?

There will be much said on this thread.

What I will state is that almost every last time I was shooting at 600 yards and watched the chrono the load that produced the lowest ES and SD and then went and looked at the holes in the paper I was never happy. The lowest ES and SD just never produced best accuracy.

That said nothing wrong with low numbers. In fact they are good.

But it changed my attitude totally. Run the chrono sometime so I know what ballpark speed.

But test ammo at a far distance and go by how tight repeatable groups are. Looking for weird flyers to indicate IFFY load. And watching for round groups as a whole. Got to where I played mostly with primers and neck tension and pretty much ignored the chrono and paid attention to actual groups.

What we found is you can have low numbers and bad groups. Or you can have decent numbers and good groups. I know what I want.

And add in seating depth to what rost said

Those are great points from experience.

ES and SD don't account for barrel harmonics.

I've read where some find the best ES (lowest) and then adjust seating depth to get the best group out of that ES. Is that real/fake etc - this is coming from F class guys.

Only fire 3 shots so you can claim single digits on both to be impressive.

HA! (But know guys who take it seriously....)

I'm a 5 shot guy and honestly, I understand that for most of my life, 100 yard sight in and then go hunt out to 250/300 with little struggle but my interests are starting to stretch out and I realize finding an "accurate" load for that typical deer hunting isn't hard and it starts to matter a lot more past those ranges. Why I've started looking/poking around guys like Cortina and F-Class John on such topics of load development.

Just hoping to get a good cabin fever discussion that's beyond "Creedmoor doesn't do anything XXXX doesn't do" type of discourse.

I tweak for consistent pressure/speed by adjusting powder type and charge weight, consistent neck tension, primer ignition, etc., and then adjust seating depth to time bullet release at an anti-node in the harmonic motion of the muzzle. That gets both low velocity dispersion and low POI dispersion.

To answer the question in the OP, sample size matters. Statistical quantities like SD and ES are only really meaningful if the sample size is large enough. Typically, a sample size of 30+ is where we start to associate some weight to variance metrics like SD. If you take a sample of 30 shots and the SD value is less than 10, that’s very good.

I`ve never done that numbers thing, and I`ve loaded thousands of rounds of match ammo. Mostly for the 308. I find a load that shoots well at one and two hundred, either with the match gun or hunting rifle, and go with it. I then concentrate on what I`m doing, couse I do f`up now and then.

Sometimes we make this loading stuff way too complcated.

Yep, a minimum of 30 is what a major American ammunition factory uses when working up loads with a new batch of powder.

👍👍👍👍

Seems that this is usually left out of the mix, or has been in most discussions on this subject.

Absolutely, larger the sample size the better and I agree. Good reason to shoot more.... which probably isn't a bad thing.

So assuming a large enough sample size to be relevant - what's the final number you want to see? Sub 10 or?

That could work. I've never tried it that way.

Seating depth was pretty much a given for me. Same barrels, same chamber reamers etc... and at that point I knew where it should be. And playing with it never really changed much.

That said I never went back to the lowest ES and played after that.

I don't waste lots of shots proving anything anymore. Especially since I'm not competition anymore. There I needed to know if things were good with 20 shot groups...

But what I do is continue to shoot what I pick at the onset, at various yardages.

One of my favorite things the last years is since we have been playing the BDC sig scopes, take a 3 inch diamond target. Put it up. Shoot one at somewhere around each of the 100s... out to 500 or 600. And see if I can keep all 5/6 shots in the 3 inch bull. I can do it most of the time. It verifies day in and day out that the load is solid.

Really for me, it goes back to the Audette. Get in the middle of the highest MV node and that should serve probably 95 % of peoples needs

Yeah, an SD of less than 10 fps is my target.

Tell ya what try putting 20-25 rounds into a 1.5” circle at 300 yards instead of deer hunting accuracy. It really isnt that easy as people think.

As a function of shooting ability or as a function of actually being an accurate load? - that's the point. Eliminate the variable and do the best you can while building the load. I'm trying to learn what does/doesn't matter with the load and to a degree then - what's the target for those data points to indicate, I've found the load - now work on the idiot yanking the trigger.

Great topic.

+1

dave

This happened to me yesterday. SD of 5.3 FPS and extreme spread of 12.8 FPS was the largest group with one of my 308 rifles.

That said, I may go back and tweak the seating and see what's what.

I want mine as low as possible, under 10 fps with 3 shot groups. That doesn’t mean “squat” at close range, say under 400 yards, but gets exponentially more important at long ranges! JMO memtb

I start out with 5s when looking for promising data with the chrony. The promising ones get repeated with 10 shots to confirm. Then its seating depth checks with 5s @ 100 yards.
Final range checks are at either 200 or 300 yards.

I currently have 2 loads that are neck and neck for going into the recipe log, so next week it's 15 rounds each at 200 or 300 yards (depending on however busy the range is) to decide.

Then when the snow clears I'll be in the hills where I check 'em again at 400 yards. I can always get to within 400 yards at whatever I'm looking at in the crosshair.

ES or SD?

SD estimates from three shots are not reliable at all.

This absolutely works. I was experimenting with ammo for a new F-T/R build last week. The load that gave the best ES and SD produced mediocre groups. I started playing with seating depth and managed to make three consecutive 1/2 MOA ten shot groups. I ran them all on the chronograph after tuning depth, and for the 30 rounds ES was 14 and SD was 5.2. I was quite happy. First match of the season is in two weeks.

Sometimes I will shoot two or three rounds of each load to just rule out what doesn't work.

In my mind - low ES/SD is an indicator of consistency in combustion. A bullet that consistently moves at the same speed is probably going to print the more consistent group time after time. Not saying the most PRECISE group but whatever it produces, it's likely to do that over and over given the nature of always sending a bullet at 2700 or whatever.

Once small ES/SD is found - then change things to find a way to make that group more precise? Seating depth seems to be the way some do it.

Which - assuming it's factual, makes sense to me. Give me the most consistent and repeatable results first and then we'll make those results better. I don't know how you can consistently make precise groups IF your velocity's ES is large.

In my experience, which is primarily with shotguns at a competitive level - consistency is paramount. So ES/SD being consistently low gives me the best chance of seeing repeatable groups (regardless of how precise they may be).

Take your minimum velocity and maximum velocity, run them through a ballistics program. Look at the difference in the drop values for both velocities at 600 and 1000 yards, it will give you an idea if you can hold your shots in the X ring.

ES!

Understood, but while doing load development and increasing 1 grain/3 shot group….very small velocity gains with each group having very tight ES’s. This was repeated for 3 or 4 load increases.

Maybe not as reliable as a very long shot string, but the groups were nearly superimposed over each other and around 1/2” for each 3 shot group. Considering it’s a rather light rifle, producing near 60 ft/lbs felt recoil….I was satisfied! With the cost and limited components available….. I guess that I’m easy to please! After all…..it’s a hunt’n rifle, not a BR rifle! 😉 memtb

I see this noted above. How is this being measured?

I've seen some examples where a load cell is used to measure what could be this parameter. That unit of measure is a force to insert a bullet into case neck.

I suppose a mathematical equation could be used to derive a neck tension value whatever that is.

Now back to ES/SD topic at hand.

Some use force, some use the difference of outside diameter after sizing and spring-back before and after seating a bullet.

The ES and SD numbers are indications of consistency only, not accuracy. If you get the numbers to coincide with accuracy, that's great, but don't count on that happening. Lots of others factors make up an accurate load. Group size first (five, five-shot groups, at least), then the numbers, if you have to have them. I seldom look at the numbers, something that has become quite a fad in recent years, along with neck tension.

Yep.

30 is generally considered the minimum threshold for a valid statistical SD.

Less may be somewhat indicative, but is not definitive.

Guys that shoot 3 or 5 round groups & think that the the data is gospel are just fooling themselves.

MM

Agree, 100%.

From a different angle. Anything is possible some things are more probable.
measurement is a combination of systematic and random errors. ES and SD are part of the systematic or Gaussian side and the reloader has some control over them. Both the sighting system and the physical system of the rifle assembly are non-linear and the optimum combination lies in a"basin of attraction" for all the inputs. Both manufacturers and shooters try to linearize the system optimizing the many components involved. When in fact a random error (ex. change in temp. and burn rate of a powder) can offset one or more of the systematic error as to cancel both, and show the resultant value closer to the midline of the Gaussian distribution or completely ruin any kind of correlation between the two (large groups). Bench shooting assumes the some linear approach, (your going to do it the same every time). The uncontrollable factors in long range shooting make it surprising the whole thing works as well as it does.

The most important part of the entire thing is : Have Fun!!

These discussions always bring to mind this from Ken Oehler that leapt out at me from the manual for my 35P purchased decades back:

Again, this is just talk/theory discussion during crap weather seasons and a lack of game to shoot.

And that's my question - can you be consistently accurate and precise without consistency of load (as measured by large or not ES/SD)?

Can you more likely repeat accurate and precise loads with inconsistent velocities that vary greatly or is it more likely that if you find a consistent load in ES/SD - make it accurate?

And yes, I'm familiar with Audette for finding the best "load". I'm more interested in this theory I've seen promulgated by guys like F-Class John and Cortina as part of their "don't care where the lands are and I don't keep that relationship a 1:1" mentality and load development that way. Cortina is obviously a well credentialed shooter.

(Selecting some level of "jump" and then finding the powder/charge that works with that is a bit of a backwards play on that I guess)

I never was that involved in the testing. Our targets where forgiving and we had to work on us almost more than the load.

Class took a lot of the human error out and demanded a smaller target.

Its good to read these things.

The 2 things that I did that may not apply anymore at all. But at least one seemed repeatable to me.

I found the distance off the lands that the groups were happy. Seemed to be pretty reliable after I had worn out enough barrels that I could just kind of ignore it and all would be good enough. I did have a rule and it was to either be off the lands or engaged. Never give or take within about .015 of the lands. In English I was at least .016 off the start of the lands best I could tell or I was engaged at least .015 or more. I think my memory is right. But since the ogive of bullets vary sometimes from bullet to bullet, hopefully not much, but they do, I didn't want to be right at that pressure making engaged and have one less or one more so to speak. It is one reason we seat off the ogive and not so much the OAL actually.

Once I had loss of accuracy I went back to the chrono and usually had lost speed, which would mean getting out of the node IMHO. So ad powder until back at original happy speed. At that point readjust the seating depth to the same relationship it was.

I'm gonna have to google and read when I have time. I cannot see why you would not chase both the speed and the seating depth as the throat wears but I never did just one or the other so it was not a real experiment so to speak.

Great read. Good topic. Glad you brought it up. Glad I get to learn.

Primers though.... if you get a great load stash that lot of primers. Changes in powder lots I could usually make work... primer changes not so much...

Rost - that's a good point, I think it's a lot of which end of the stick you approach from. I'd be shocked if the best/most consistent load also wasn't one that showed it in ES/SD for those components selected.

How you arrive at it - might not matter. Or you might not even measure it but are "there". I know a lot of people who don't own a chrony. Shoot at 100, shoot at say 600 - measure the drop and plug into software to arrive at what their speed must be - if they have utmost confidence in the BC being accurate.

It's all another way to catch fish I guess. Just wanted conversation that was deeper than cartridge comparisons.

ES/SD are a measure of something that has already happened, not what can happen. They are a math relationship of systematic errors, nothing more or less, they exist whether you want to look at them or not. Your are asking if following the procedure to get what you like in them will repeat the same result. The answer is yes if you repeat the random errors the same way, which you can't -- thats why they are called random

Caveat is that it depends on how I shoot those 3-5 round groups. Some times I put a target up and shoot 1 shot now and then over the course of a week. yes it tests the zero. But it also tests the accuracy.

Sometimes I overlay and measure.

But you dont' always have to have large numbers of shots all at once to confirm.

OTOH if I am shooting a 20 shot plus match, then I need to know what heat etc... does to the group as you get to 20.

In theory as I've noted, if I put out my 3 inch target at any distance from say zero to 600 yards like I do at home, and I rarely miss that, I'd say for a hunting load it proves the point well enough.

Granted a few 3 or 5 shot groups prove that you may or may not be homing in on a good load. A lot of those groups will confirm or deny.

Then there was old 00. I can't recall his name be we called him Double Ought. Heck of a shooter. Maybe thought too much about technical though. He weight sorted cases or maybe it was volume. Anyway his cases were always numbered. I have no clue anymore which way he fired them, but it was that as the gun got hot, the pressure, speed etc.. went up.. or was it that the barrel grew in size and it went down? I dont' recall his theory. Anyway the answer was to fire cases in order such that you either were building case capacity or not and that affected velocity to match whatever was happening as the match went on.....

I will and have admitted this. I generally dont' take the time to care WHY something is happening. I just want to know that its happening. And thats where my input gets a bit iffy. I can make it work well enough for my uses. For yours they may differ.

I am totally convinced though that having the most accurate consistent load out there negates variables and allows you to make more mistakes, and get away with them. And it also allows you to know that the mistakes are YOURS and not the equipment and I love it when I know its me and not the gun.

I have had some really wow moments like a tack driver 308 with an MTU contour 26 inch tube on it. Missed a standing still spike shot at about 310 yards. Sent for the head. Nothing happened. I should have stopped. So I shot for the lungs. Nothing happened. Did it the 3rd time. No results. We look for the deer after it ran off and found no sign of a hit. I had dialed the elevation. Found out at home the scope had died.... I should have realized that after the very first shot and stopped. But it taught me that lesson and it happened again some years later very similar around 450 yards and when the first shot missed I stopped. Somehow that gun was off zero ... scope was fine. Gun was just off.

5 shot group @ 100 ES 76



10 shot group @300 same load same day



The ES showed itself at the 300 mark but still not bad. While with tuning I cut the ES down to 30 which is ~60%, my groups didnt shrink 60%. 🤔

The notion that you need 30 samples comes from the fact that if you are doing the basic Z test (the one they start you out on in basic stats), you need about 30 samples to meet the assumption that you really know the long term mean of the process. This is also about the point where the T Test (which everybody uses) and the Z test (which practically nobody uses) merge and become the same. It has nothing to do with the sample size needed to estimate ES or SD.

Measures of dispersion, like range (which shooters call ES) and standard deviation are harder to pin down than estimates of means. For example, I just ran a simulation with 30 data with SD = 15, and the estimate of the mean was only reproducible to between about 11 and 18.5. You can get a good estimate of the mean with a smaller sample than an estimate of SD.

SD and ES can be converted from one to the other. For a sample of 5, divide your estimated ES by 2.3 to get an estimate of SD.

SD of MV usually matters very little, so long as it is something reasonable, say below about 35 FPS. Since variation does not add linearly, the total variation will be almost entirely governed by the largest source of variation, which is normally not MV.

Interesting. Thanks. This is neat.

I might be thinking about this wrong but hear me out.

ES of 75 - shoot a .75 MOA group
ES of 10 - shoot a 1 MOA group

Which one would I feel best about reliably repeating those group sizes over a period of time (assuming condition not a factor, 10mph wind or not etc) and assuming nothing else changes like powder lot, primer, seating depth etc.?

Does that variability in the ES75 group's ability to repeat actually matter? That is to say it might shoot a .75 or 1.25 due to ES but that's NBD if 2.0 MOA is good enough.

So the ES10 offers an "advantage" because it's more likely to continually print 1moa but the standard is 2moa - so who cares?

Probably thinking myself into a hole at this point lol.

The extreme spread and the standard deviation are not a measure of errors, they are a measure of normal distribution of a combination. We use past data points to predict the future.

You may say there are "errors" in our brass, bullets, powder, etc. No, an error is an unintended mistake. The variance in our components is the product of normal distribution. When we sort components, we are attempting to make a smaller, more consistent population by excluding the outliers. This, hopefully, results in more predictable velocity. Velocity will still have normal distribution, however the variability will be smaller and thus a smaller SD. We continue to measure things like seating force, neck tension, runout, and so on to cull errors.

Statistical analysis determines probability of an output using given inputs, based on previous data. The probability of outliers is the inverse of our confidence. After all, anything CAN happen. That doesn't mean it is likely. The larger the historical data sample, the more confidence we can have predicting the future.

Agreed - not looking to use ES/SD to predict a load as the most accurate, that it's likely to be the most repeatable. An accurate load that's not repeatable from string to string is what I'd be looking to avoid, using SD/ED as a measuring stick for that likelihood.

Basically, muzzle velocity variation only matters if the rifle and shooter are able to shoot the normal distribution (precision) at a range which velocity variation results in more drop than the rifle's level of precision.

If a rifle is a 1 MOA rifle, velocity variation won't be critical until the standard deviation could result in more than 1 MOA of drop variation.

So what do you think is a reasonable SD/ES for a 3000 FPS cartridge?

Follow Rost's advice & pay more attention to which loads are the most accurate on the target....................in the end that's what matters most.

MM

Two guys that “get it”

Another comment: The reason that major ammunition factory I mentioned uses a minimum of a 30-round SD is they're trying to make ammo that will tend to group well enough in a bunch of different rifles, mostly factory. And in my experience that works pretty well. Some of it has even averaged 1/2" or so for 3-shot groups in some factory rifles.

Of course, this ain't small enough for some more particular 21st-century hunters....

What creates the harmonics in any given barrel and can harmonics be affected or are they simply inherent in a piece of steel at X length? Unchanging.

Barrel bedding also affects harmonics--which is why one maker of very accurate rifles fully-bedded the barrels of his rifle in very stiff stocks. But even then groups would vary some with different loads....

Bud in a perfect world lowest ES/SD would win every damn time if all conditions were perfect, equipment even steven and there were no human interactions. It isnt a perfect world.

Good read here

https://www.angelfire.com/ma3/max357/houston.html

Excerpt

For the most part, shooters arrived at the warehouse with troubles. Their rifles were inconsistent — one group in the teens, the next in the .3’s — for reasons they could not fathom. Others had consistent .25" to .30- something rifles, an accuracy level guaranteed to put a competition shooter down near the bottom of the pack. With the list of potential problems significantly narrowed by the elimination of moving air and dancing heat waves, the answers were easier to isolate in the warehouse, and shooters drove hundreds of miles or flew into Houston to get to the source of their tribulations.


ES/SD had nothing to do with it.

Every thing can be expressed as a wave function, including your body, (one of the first calculations on any physical chemistry or wave equation finals). The question what type, standing, sinusoidal, Bessel. longitudinal, etc.They are called harmonics because of their standing wave characteristic, repeating nature, ( they are not harmonic by a math definition). Think of a drop of water hitting a pool. The first wave is a peak, then each surrounding one is a circular one with a diminishing amplitude. Bessel functions. They appear to be harmonic if the instrumentation used set up to detect other types of waves.

It really depends on what you're doing with it. For example, 100 FPS ES in a .308 Win shooting 175 gr GMM would result in about 8" of vertical at 600 yards. Combine that with 1 MOA shooting, you have a potential of 14" of vertical if you break your shot perfectly every single time. I wouldn't want to hunt with that load at that range. It would be unethical. Target shooting? Knock yourself out.

If you're hunting 300 yards and in, it would take an extreme example to make it have much effect.

That's because they weren't shooting far enough for ES/SD to matter.

This 1000 yard group with my Palma rifle gives a good visual of velocity variations showing as vertical on the target.

That's exactly right, when shooting my short range Benchrest rifle I very seldom get out the chronograph, when shooting my long range rifles working up a load my chronograph is always there

I haven't played with SD and barrel harmonics in centerfires but, I have in air rifles. Same principles. Seems to me that finding a node in an Audet/barrel harmonics test makes your rifle more forgiving of bigger SD's and tiny SD's make your rifle more forgiving of not being right in a harmonics node. Ammunition manufacturers can only play with SD since they're loading for everybody's rifle. The question then, is which gives you the most forgiveness or biggest benefit - tiny SD or harmonics node, since you really can't chase both. Watching the wet noodle videos of barrels during firing, I'd guess an Audet/barrel harmonics node is going to give you more benefit than a tiny SD and should be sought first. My question would be, after finding the harmonics node can you then chase SD to any appreciable extent? Is that what that Cortina guy was doing in the video with OAL?

Thanks for making me think on a Saturday morning!

Check into structured barrels if you are curious about solving the problem using SD and correlations with and I use the term loosely "harmonics". They are based on the principle that tubes have more structural rigidity than rods. They also have the benefit of better cooling and are substantially lighter that the same size "bull" barrel.
Also any videos of "noodles" are due to the "too slow" pixel rate in the video equipment, If you choose a smaller bifurcation interval it doesn't give the same modeling.

When searching for the proper muzzle exit time you're trying to hit the dwell period when the muzzle movement is slowing down before it hits its peak. A slight variation in velocity will hopefully occur in that stage of the barrel movement.

Sure you can. The method was previously mentioned in this thread.

Ok, Jordan, you just made me skim back through all the posts. I assume it's where you talk about tuning for consistent velocity/pressure (SD) with charge weight, powder, etc. then tuning for a barrel harmonic anti-node with seating depth. Do you do the Audet varying seating depth instead of charge weight? Or, how do you do it? Group size?

Does the cake next to your name mean it's your birthday? If so, Happy Birthday!

I noticed that this entire post is about ES and SD. Only in velocity.......ES and SD in pressure is equally important. And yes you can be having some wild pressure swings and have low ES and SB on velocity. And vise versa. Its a mistake to only look at half the picture.
Charlie

I don't doubt you are correct, Charlie, but that doesn't make sense to me. I look up to you and Jordan, too, for that matter, as being way more knowledgeable and experienced in all things ballistics than me. Whatever bones you want to throw my dumb ass by way of explanation is much appreciated.

This discussion of measurement, nonlinearity, harmonics, and variation have some incorrect assumptions and concepts that are muddying the waters.

In experimental labs, we differentiate between measurement uncertainty and error. Measurement error is the difference between the measured value and the true value of the quantity being measured, and is usually unknown due to limited measurement precision. Systematic error relates to an offset built into the measurement, such as an instrument calibration error. Random error is related to the underlying variation in the quantity being measured as well as the limited precision of the measurement. What is more relevant to this discussion is measurement uncertainty. Type A uncertainty describes variation in a measurement due to underlying variation in the quantity being measured, while Type B uncertainty is the result of everything else (resolution limitations of the instruments, etc.).

In this case, we are discussing Type A uncertainty in speed measurements. Usually, multiple sources of uncertainty are combined by adding in quadrature, and we see that the combined measurement uncertainty is dominated by a single source as that source approaches 3x larger than other sources. I.e., if speed variation results in POI changes that are 3x smaller than those due to the precision of the shooter/rifle system, wind effects, etc., then we can essentially ignore speed variation in estimating POI of a given shot.

I’m really not sure where you’re going with the nonlinearity comments, but for clarity, you’re talking about dependent (output) variables that have some non-unity exponential dependence on independent (input) variables.

Barrel harmonics, in this case, have noting to do with specific wave functions or standing waves, and simply refer to integer multiples of the characteristic frequency of the muzzle oscillations. I.e., timing bullet exit with the anti-node of some integer multiple of the periodic motion of the muzzle. Of course, the characteristic frequency of the barrel is dependent on barrel length, stiffness, termination nature, damping sources like bedding, muzzle weights like tuners, etc. In figuring out how to time bullet exit correctly, we can think of it as tuning for consistent acceleration over the length of the barrel, and therefore, consistent bullet exit speed and barrel time, so that the bullet exit is at a similar point in the muzzle oscillation every time. And then tuning the initial position of the bullet (seating depth), and therefore the total distance traveled by the bullet, to time the bullet exit with the muzzle position being at an anti-node.

An alternate approach is to accept some bullet speed variation, but time bullet exit with the muzzle position approaching the top anti-node so that faster bullets exit when the muzzle is at a slightly lower position, and slower bullets exit when the muzzle is at the top of the anti-node. At some distance downrange, vertical dispersion is minimized by slower bullets having a slightly higher trajectory and faster bullets having a lower one, but for other distances, the speed variation causes an increase in vertical POI dispersion relative to the approach that minimizes both speed variation and POI variation.

Yes, and it’s the same method referred to in other posts and used by Cortina, F-class John, etc. I personally don’t use the Audette method because it relies on too much statistical uncertainty for my tastes. I first tune for small SD and then shoot groups with varying seating depths in 0.003” increments to get to an anti-node.

It does. Thank you!

No matter how carefully one loads ammo, there will always be velocity variations.

This is the entire point of the Audette. It isolates the exit time that you have described and minimizes vertical POI variations at long range

Absoluty

That’s correct, and it’s because we usually only talk about peak pressure. In reality, integration over the entire pressure curve is what ultimately correlates with total acceleration, and therefore, barrel time and bullet exit speed. So it’s possible to have different pressure curves with different peak pressures, that integrate to the same total pressure over the bullet path along the barrel, resulting in identical bullet exit speeds.

True, but less is better.

The principle behind the Audette method minimizes vertical POI variations for a given amount of speed variation and a given distance, but perhaps not compared to a load with significantly less speed variation, which minimizes POI variation at all distances.

The ideal approach would both minimize speed variation, and time bullet exit on the upswing of the top anti-node.

Where the muzzle is in it's cycle when the bullet exits can be changed by means of moving weight....a 'tuner' for lack of a better term. If there's no adjustable weight to change where the muzzle is at the time of the bullets exit, other things are used to 'tune' this. Chiefly powder charge, different powders, seating depth, neck tension and different bullets. In other words...normal things we do to 'tune' a barrel.

I did this testing last season with a tuner. Nothing is changed but the position of the tuner as it moves further out the barrel. You can clearly see when the muzzle is at it's 'dwell' points and when it's moving between those two points. It's apparent that the amplitude changes as the tuner moves out. This 'sine wave' pattern repeats over and over again.

I believe the Audette accomplishes both

That's very similar to the target-test I do on rifles used at longer ranges. Have found it's easier and faster than the classic Audette....

Got it. Thanks

How do you control the 'barrel' variable? Barrel temperature plus the condition of the surface of both the lands and grooves must come into play, right?

The problem is that the method doesn’t provide any way to reliably know or confirm that speed variation nor vertical POI variation are minimized. One shot with each load doesn’t reveal much.

It reveals everything. Hate to have to go over it again because you know how it works

Groups are shot with the loads in the node and invariably one of the loads will shoot great with minimal vertical

My method as well to show the "effect" of a higher ES/SD to folks that don't appreciate what you're trying to achieve.

I want single digit SD if at all possible for the longer range guns. I find it easier to achieve in the longer barreled rifles, whereas I really don't sweat it than much in the 300 yds and under hunt rifles/carbines.

Which doesn’t account for barrel harmonics.

You both are assuming the barrel is “pointing” in the exact same place when the bullet exits to lay that much weight to velocities to calculate drop

In a proper node, higher velocity rounds exit quicker when the muzzle is pointing lower, but drop less

Lower velocity rounds exit later when the muzzle is pointing higher, but drop more

The cumulative effect is minimal vertical dispersion and is the characteristic of the best load

CumGargler, how's ES/SD on this ammo? Does it over penetrate or not offer enough penetration on the thick armor cockroaches wear? Is it worth the cost, or going through as much as you do to keep the hoards of roaches in your restaurant at bay, you find regular table salt more cost effective?

No dumbazz, that's not what I'm saying. I understand that velocity is a variable and that the barrel is in constant motion. You want to time your muzzle exit when the muzzle movement slows down and is just before it's peak. I've played with a chronograph, quick load AND pressure trace, have seen how velocity changes exit time...

Great post. I can tell some stories about newbie handloaders shooting schidt for groups and coming up to me at the range and telling me their sd and es numbers were low. I finally got tired of one guy bugging me, as he was having issues with his "precision" rifle and loads and only relying on the chronograph. I told him to "throw the fu cking chrono away or leave it at home. Shoot your rifle and let it tell you what it likes". I know that sounds harsh, but don't ask me stupid questions more than about 2 times. You may not like the answer I give you!!! That goes for anyone.

I don't use a chrono that gives me es and sd numbers, as I could really care less. I know what my ammo and rifles do at just about any distance because I test them. I have the hard numbers on paper. The lazy fu cks don't want to do that and are looking for an easy way out. There is no replacement for actually getting out there and doing the shooting.

The only time my loads were tested, was when I was at a range/rock quarry in the national forest and a guy wanted to see what es sd numbers my loads were producing. He kept eyeballing my groups and was struggling big time with his loads and rifle. The funny thing about that was it was a Tikka. One of the early superlight 223's with the fast twist barrel. I was shooting one of my Winchesters, before I even owned a Tikka (around 2009-2011). Actually my competition rifle at the time. A souped up Winchester (FN PBR XP), that a lot of SWAT/police guys used back in the day. When he had me run my loads across his chrono, I fired 10 shots into a cluster of about .6" on paper. The sd was 7 or 9, and the extreme spread was small as well. He asked, "what is it exactly you do again". I said, what do you mean? He said, "what do you do for a living". I said I'm a "welder". He shook his head and said, "well you just made an aeronautical engineer look pretty bad!!". Are the sd/es numbers of my other loads pretty small?? I don't know, but I know they shoot good:


That guy is actually a friend of mine now. Funny, the people you meet out in the national forest, or at ranges. Some get it, some don't..

I always use the high performance stuff.

It’s like a Nosler Partition for them tough bastids

Not just drop though.. the slower bullet also spends more time in the wind.. correct? In theory you should pick up more horizontal dispersion also, say with a 3 or 9 o'clock with the slower bullet.

And the way I learned it, the lower velocity exiting at a higher point in the barrels recoil, really had a greater effect when it comes to handgun velocities.

I don't think anybody has said that "good numbers trump accuracy", just that some want both.

Well played, you're nearly tolerable when Burns isn't around.

If you don't intend to shoot long range, mostly, it doesn't matter much.

Flight time differences would probably be measured in 1/100ths or 1/1000’s of a second, so time exposed to wind wouldn’t make any significant difference for horizontal dispersion

Thanks all for the conversation, it's been....interesting.

I realize, I've probably not been as clear as I wanted and that's ok, sparked some interesting conversation and that's the point of this.

If things stack up right this summer, hope to get some time out at Lodi for shooting longer than I typically can.

Just for conversation sake I ran the numbers with Strelok Pro using my 6mm SLR data (think 6mmC +P) Berger 105 Hybrid (fictional load, my load has an SD of 7) and a 10MPH cross wind, same conditions. I used the high and low MVs for the fictional load.



So at 600 you're looking at 2.3" delta in drop and .5" less wind.

at 1000 you're looking at 8.8" delta in drop and 1.4" in wind delta.

Again, I don't think anybody has said that stats trump accuracy, just that for the longer distances it's better to have both good accuracy and stats.

50 fps between shots is a pretty big spread. I would put that load in the “poor” column

Nevertheless, even with that load, you can see that windage isn’t significant unless you think you can actually hold your POA to the accuracy of 1/2” at 600 yards or 1.4” at 1000 yards