Chronograph numbers
- Thread starter Aguila Blanca
- Start date
I went Chrono crazy this morning, trying to determine if I wanted to buy another Labradar so I borrowed one from a friend with a recoil operated triggering device and shot it head to head with my ProChrono, Magnetospeed Sporter and Shot Master electronic target
https://thefiringline.com/forums/showthread.php?t=612683
that was with 55 gn factory Lapua I was shooting just to get the brass from
later on I did some three round load workups with 80 gn Bergers and IMR 4166 just to get an idea of how they would work together. Notice that low ES/SD does not always correlate with group sizes or vertical dispersion. I will be going back looking at a couple of those loads with larger numbers of shots
https://thefiringline.com/forums/showthread.php?t=612683
that was with 55 gn factory Lapua I was shooting just to get the brass from
later on I did some three round load workups with 80 gn Bergers and IMR 4166 just to get an idea of how they would work together. Notice that low ES/SD does not always correlate with group sizes or vertical dispersion. I will be going back looking at a couple of those loads with larger numbers of shots
Attachments
As near as I can tell, tuned charge weight center values for velocity flat spots and barrel whipping flat spots are both independent of velocity SD and of each other. The ideal is to get them all in synch, which can be a challenge with that many independent variables. Barrel tuners exist to try to eliminate the barrel whipping variable from your charge weight and seating depth tuning.
Part of the value of low velocity variation numbers is they help keep individual rounds on the high or low end of the extreme spread from taking individual rounds outside the tuning flat spots when temperature changes are enough to affect pressure and velocity. In effect, low ES extends the range conditions under which your load remains tuned.
Part of the value of low velocity variation numbers is they help keep individual rounds on the high or low end of the extreme spread from taking individual rounds outside the tuning flat spots when temperature changes are enough to affect pressure and velocity. In effect, low ES extends the range conditions under which your load remains tuned.
Barrel vibration calculator
http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm
http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm
Honestly the more I shoot the less I give a darn about chrono numbers. Only thing I find them useful for these days is getting a velocity for come up's. The holes in the paper tell me all I need to know about charge and seating depth. Look at those workup targets I posted above, over half had single digit SD's but the group heights went from .3's to over a inch. I will spend my primers and powder exploring 20.3 and 21.2 loads with 10 or 15 rounds each, see which one gives me the best group average then tweak the seating depth at 600 or 800. I am over the live or die by the chrono stuff. In the future mine may get pulled out for extreme temp swing velocity checks but that is about it. A friend of mine who is a high master FTR shooter confided in me recently that it has been three years since he last used a chrono. And this guy can take a .223 with 80gn bullets and keep 20 shots under a MOA at 800
The way to prove it to yourself is to find two equally tightly grouping loads at short range, but loads with a significantly different SD, and shoot both at your longest range and again at about half that range to see if you can't discern a difference on one or both of the targets. That would keep velocity spread independent of the other factors so you can see what difference it does or doesn't make by itself.
I’ve had some really atrocious SD and ES numbers shoot amazing out to 400 yards. By amazing I mean under 2moa with iron sights. As in ring the 8” gong every time with iron sights. This also shooting a low BC Speer hot core bullet that should absolutely start to show how velocity starts to cause vertical stringing at range at 400 yards. I’m not saying high ES won’t show up as vertical stringing ever. I am saying that it doesn’t matter to me for about 90% of my reloading. I do get to go to the 1000 yard range at Butner on occasion. So when I do, I dust off my long range gun and get anal with reloading.
I specifically wanted to revisit this because I believe we can use sloppy equipment and technique in many areas, and still make ammo that far exceeds factory ammo accuracy potential. I bent the expander stem of my 7.7 Jap die a few months ago. Got a case stuck in the die and tried to unstick it by punching the decapping/neck expander stem. I bent the crap out of it. Not having any other option if I wanted to shoot the next day, I hammered it as straight as I could get it by hand (.020 off center using a runout gauge). Like I messed with it a while and it was as good as I could get it. You can plainly see it off center in the die, and yet ammo made from cases sized from the die shoot at 1.5moa with iron sights at 200 yards. I can’t declare that it wouldn’t shoot better or not, as 1.5 moa with iron sights is about as good as my eyes are. I think we fret a lot of things that don’t matter as much as we think they do... unless you’re shooting bench rest or 1K competitions.
Pistol? I can’t imagine ES or SD making a hill of beans difference to 99% of the shooting public. I have .45acp ammo that has SDs of 22 that hits a 6” plate at 50 yards off hand almost every time. Sure some of you guys can easily do that and beat me doing it. I know this. But it’s better than a large majority of the shooting public can do. And so I’m ok with my occasionally high SD ammo. That at times holds tighter groups than lower SD ammo. YMMV.
Last edited:
Been there done that Nick. I had not shot my .260 rem in ages, having been seduced by the 6mm low recoil and accuracy. About a year ago I decided to see if turned necks really made a difference and having turned all of my 6BR necks I used the 260 Rem for the experiment. My logs indicated a ES of 17 and SD of 6 at 44.5 gns of 4831 SC using Barnes 140 gn Match Burners so that was what I ran at. I put up a target at 850 yards and the 10 round group with the turned necks had vertical dispersion of six inches with nine of the ten in a tight 4 inch group. I decided to play with annealing again ro see if I could eliminate those annoying odd flyers.
I loaded up 30 more rounds, annealed the necks on 20 and pulled back to 300 yards.I have posted that target on here more than a few times. Three groups of ten. The first ten annealed ES of 168 SD 56 group size .813 MOA, Second ten annealed 47 ES 13 SD. Third group 97 ES 31 SD group size 1.1 MOA. All rounds had powder measure to plus or minus .02 grains. BTO was confirmed on all 30, primers seated to .003 - .006 below flush, runout less than .001. In other words match quality rounds
That was the same load that had shot 9 out of 10 rounds into .5 MOA at 850.
That was also when the light went on that the ES /SD can vary tremendously on the same load depending on your hold. The first annealed and the unannealed group were shot with a jean jacket on, when I shot the third group the jacket had been removed
Anyway just my opinion here, but now I turn the necks and anneal all of my cases but ES/SD is the least of my concerns. The groups tell me all I need to know about my loads.
I loaded up 30 more rounds, annealed the necks on 20 and pulled back to 300 yards.I have posted that target on here more than a few times. Three groups of ten. The first ten annealed ES of 168 SD 56 group size .813 MOA, Second ten annealed 47 ES 13 SD. Third group 97 ES 31 SD group size 1.1 MOA. All rounds had powder measure to plus or minus .02 grains. BTO was confirmed on all 30, primers seated to .003 - .006 below flush, runout less than .001. In other words match quality rounds
That was the same load that had shot 9 out of 10 rounds into .5 MOA at 850.
That was also when the light went on that the ES /SD can vary tremendously on the same load depending on your hold. The first annealed and the unannealed group were shot with a jean jacket on, when I shot the third group the jacket had been removed
Anyway just my opinion here, but now I turn the necks and anneal all of my cases but ES/SD is the least of my concerns. The groups tell me all I need to know about my loads.
Here's the problem: For any load tuned to muzzle swing, there will be near perfect compensation for velocity variation at the tuned range, so velocity variation won't matter at that range. The trick is to see how the same load shoots at some other significantly different distance for the purposes of shooting multiple-range matches or targets. You can model this in a ballistics program by telling it to zero at a particular tuned range, like 300 yards, then seeing how the vertical POI changes at other ranges (difference in total drop or difference in come-ups to have it in MOA) when you change MV between the extremes of your velocity extreme spread. My contention is that IF ALL ELSE IS EQUAL (no other variables are changed, like neck annealing one set but not the other, or shifting shooter position or changing shooting jackets, etc.) a lower SD will produce lower vertical dispersion at ranges OTHER than the tuned range.
Equipment-wise, you are in a good position to do a simple multi-range test of this principle. Set up your shot marker with an empty frame at a tuned range and elevate it so your bullets will pass through the middle of the frame on their way to a longer range paper target that is your actual POA. Compare the real and the virtual target for vertical dispersion. This eliminates variables by measuring the exact same shots at both ranges. My expectation is the ballistics software predictions will be born out, but if you found otherwise, we'd have a really excellent physics puzzle on our hands.
Equipment-wise, you are in a good position to do a simple multi-range test of this principle. Set up your shot marker with an empty frame at a tuned range and elevate it so your bullets will pass through the middle of the frame on their way to a longer range paper target that is your actual POA. Compare the real and the virtual target for vertical dispersion. This eliminates variables by measuring the exact same shots at both ranges. My expectation is the ballistics software predictions will be born out, but if you found otherwise, we'd have a really excellent physics puzzle on our hands.
that experiment would be extremely hard to do at my range Nick. From 100 to 200 is level. That is the short range The long range from 300 to 500 is a downhill slope from 500 to 600 fairly level but well below the firing line then 600 to 800 is uphill. I could probably rig someting up from 100 to 200 but that would be about it.
My own theory is that very minute changes in hold and barrel harmonics would explain slightly faster shots hitting lower and slightly slower shots hitting higher. Anyway I have been discussing this with the better shots at the club. I can think of two who I have never seen chronoing a round. These are guys who shoot 590 + aggregates match after match. Turns out they both use the Satterlee method, seems to work for them
I did a break in on a new .308 barrel this morning. I have a Ezell tuner on it and will be doing a simple charge weight workup at 300 to pick
charge depth, setting seating depth to magazine length and using the tuner to fine tune the groups. No chrono will be involved until the load is finished and I need to get my scope come ups
We will see how it works
My own theory is that very minute changes in hold and barrel harmonics would explain slightly faster shots hitting lower and slightly slower shots hitting higher. Anyway I have been discussing this with the better shots at the club. I can think of two who I have never seen chronoing a round. These are guys who shoot 590 + aggregates match after match. Turns out they both use the Satterlee method, seems to work for them
I did a break in on a new .308 barrel this morning. I have a Ezell tuner on it and will be doing a simple charge weight workup at 300 to pick
charge depth, setting seating depth to magazine length and using the tuner to fine tune the groups. No chrono will be involved until the load is finished and I need to get my scope come ups
We will see how it works
Jim Watson
New member
Agree, except; +/- 1 SD includes only 68% of your long run velocities, you should go by ES because your very fastest and very slowest shots count, too.
I remain to be shown where the mathematical manipulation leading to SD is of value in actual shooting.
Today I shot 50 down the new barrel just breaking it in. It stopped coppering about the tenths round so I started playing with the tuner. All rounds had the same charge which came from from a old load workup with a factory barrel, longer barrel, no tuner so I doubt the velocity and ES/SD was the same.
Today just moving the tuner out 2 clicks at a time most groups were around 1.5 MOA until the last five when suddenly 4 went in the same hole and the 5th off in lala land. That was using some old LC that had been through my AR 10 a few times.
I have 100 new Starline cases in the mail and plan on moving the target to 300 or even 600 using that same load and adjusting the tuner up and down. I bet when I get a load to shoot it will do so from 100 to 850. Only load tuning I plan on is adjusting the harmonics with the tuner. I will chrono for numbers at the end but I am not going to worry about velocity until it groups
Today just moving the tuner out 2 clicks at a time most groups were around 1.5 MOA until the last five when suddenly 4 went in the same hole and the 5th off in lala land. That was using some old LC that had been through my AR 10 a few times.
I have 100 new Starline cases in the mail and plan on moving the target to 300 or even 600 using that same load and adjusting the tuner up and down. I bet when I get a load to shoot it will do so from 100 to 850. Only load tuning I plan on is adjusting the harmonics with the tuner. I will chrono for numbers at the end but I am not going to worry about velocity until it groups
That will be the object of the exercise. Find that one-holer tuning at a particular range and see if it doesn't need re-tuning to get the best vertical dispersion at other ranges. I'm expecting the laws of physics to hold up, but eagerly await your results with it, either way.
The point of gathering stats is to predict future performance potential. The problem with ES is it only counts the two most extreme data points, where SD takes all the data points into account. As a result, SD is more consistent than ES for the same reason larger sample sizes are more representative of performance than small ones are. SD is an estimate of sigma, the population standard deviation, so it estimates the size of the normal bell curve distribution your data is expected to have. That lets you find not only where 68% of future datapoints will be likely to fall (±1 SD on the bell curve), but also where 90% will fall (±1.6 SD's) or where 95% will fall (±2 SD) or where 99% will fall (±2.6 SD) et cetera, to predict scoring potential.
You can see this in Geoffrey Kolbe's paper, here. You have to fire about 6 sets of 7-shot groups, or 42 shots, to get the same certainty of predicted future results about 15 shots will give you when using SD.
Jim Watson said:
The point of gathering stats is to predict future performance potential. The problem with ES is it only counts the two most extreme data points, where SD takes all the data points into account. As a result, SD is more consistent than ES for the same reason larger sample sizes are more representative of performance than small ones are. SD is an estimate of sigma, the population standard deviation, so it estimates the size of the normal bell curve distribution your data is expected to have. That lets you find not only where 68% of future datapoints will be likely to fall (±1 SD on the bell curve), but also where 90% will fall (±1.6 SD's) or where 95% will fall (±2 SD) or where 99% will fall (±2.6 SD) et cetera, to predict scoring potential.
You can see this in Geoffrey Kolbe's paper, here. You have to fire about 6 sets of 7-shot groups, or 42 shots, to get the same certainty of predicted future results about 15 shots will give you when using SD.
I think that business about the two Data Points being the extremes is misleading.
It does not matter if you shoot 100 rounds or two rounds, you still have two data points that define ES. 100 might well be closer next two extreme up.
100 might increase the ES by X amount, sans some badly done ammo.
ES is just one set of the tools but it is not stand alone, average is important for duplicating a load (powder variation or changing powder)
I just re-ran hand loads for the 270. Matched the new loads to the old gr wise. The new loads were unacceptable. I had some of the old ones, ran it past the LabRadar, hmmm, my new loads are lower velocity by 75 fps.
Next step, two powder adjustments and take the new rounds down and test again.
Yep, I now have 1 inch groups (I do not normally test that gun to 5 as its hunting rifle and all we care is that the first 3 shots hit close to center, up an inch and want at least 1.5 inch group.
Normally the 270 will shoot 3/4 to 1 inch. New loads, 1" consistently. Ok, good enough. The Chrono too the guesswork out of what the difference was and what direction to go to get it back in.
And yes I can keep adding 3 shot groups to the Chrono and get a data set of 9 to see what the ES is doing and what the Average looks like.
It does not matter if you shoot 100 rounds or two rounds, you still have two data points that define ES. 100 might well be closer next two extreme up.
100 might increase the ES by X amount, sans some badly done ammo.
ES is just one set of the tools but it is not stand alone, average is important for duplicating a load (powder variation or changing powder)
I just re-ran hand loads for the 270. Matched the new loads to the old gr wise. The new loads were unacceptable. I had some of the old ones, ran it past the LabRadar, hmmm, my new loads are lower velocity by 75 fps.
Next step, two powder adjustments and take the new rounds down and test again.
Yep, I now have 1 inch groups (I do not normally test that gun to 5 as its hunting rifle and all we care is that the first 3 shots hit close to center, up an inch and want at least 1.5 inch group.
Normally the 270 will shoot 3/4 to 1 inch. New loads, 1" consistently. Ok, good enough. The Chrono too the guesswork out of what the difference was and what direction to go to get it back in.
And yes I can keep adding 3 shot groups to the Chrono and get a data set of 9 to see what the ES is doing and what the Average looks like.
One of the joys of statistics: the larger the sample the more likely the range of values (i.e. "extreme spread") is to be larger.
At the same time the standard deviation is very likely to get smaller as the formula involves dividing by the number of observations (yes there are square roots involved but the effect is the same just not linear)
scatterbrain
New member
When developing a hunting load or sighting in a hunting rifle I shoot 10 shot groups. Why? The more holes in the paper the better the data for making a judgement. Unclenick said it well.
Yes, I know what it is called. But extreme in the real world has a far different aspect than match or statisticians.
So, if I shoot 5 bullets and the spread is 10, its still extreme.
The business about two shots defining extreme is the worst part. Duh. I mean really, its what we want to know. What is the spread?
If bullet B is withing 2 FPS of bullet A, that also tells you something.
So statistically we diss the two points because they are not statistically valid (too small a sample). But but the very definition they can never be valid.
And therein I heartily disagree. If our 5 or 10 rounds are 35 FPS of each other, we have done a good job reloading.
Equally the factory 270 that was 200 fps off and was way off on the target also told me something. It was not typical. It was wild. For typical I can throw it out.
Now if that keeps happening, you can throw the ammo away (well pull the bullet and turn it into something useful)
The same with other loads, if I have one round way outside the norm, there is something wrong with THAT round. I can throw it out (delete it) and I can look for what and why it was. Almost certainly an off powder charge.
If I am deep into tiny holes (or competition) I can throw those out and or I can double check the powder charges.
Each field comes up with its own terms. That does not mean you can't challenge them.
VS (Velocity Spread) would be a good one to replace it with.
The Fire Sprinkler system world uses a term for pressure that has not velocity component to it, aka Residual Pressure.
The rest of the tech world uses the term Static Pressure. Maybe it makes Sprinkler engineers feel special to have their own definition. Pewee on them.
And don't even get me started on Surveying that breaks a circle into 90 degree segments and then makes you cross calculate what that means cal wise to get the right number turn the transit to 225 degrees because you cross 3 of those 90 deg segments.
You want to put errors into something, that is the way to do it. Statistically its a really bad idea.
How many times do you shoot at an animal 10 times? You get one of those thing barrels that hot and it shifts the POI, what does that tell yo for hunting?
More valid for hunting is 3 shot groups and let the gun cool off each time. Rarely do you shoot more than one and even more rare 2.
So I shot 9 or 12 shots but I do it in 3s let the gun go cold like it would be when you make your first shot and I see where they fall on the target.
If it shoots a 1 inch group and its 1-2 inches above the aim point, good to go.