Load Development Using Chrono Velocity Ladder

[RegionRat]

First question is that at what distance are those groups?
Note: Group sizes could be broken in 2 components: Vertical spread and Horizontal spread.
The MV SD/ES would affect almost only the Vertical spread, and it would be very critical at very long range.
Example, at distance of 300 yards SD mean variance is inconsequential to the group size.
Even at 1,000 yards, a 1% MV spread, say + from 3000fps +- 15 fps. Those +-fps would ammount to +- 0.1mrad or so depending on Bullet G7 and MV.

Long Benchrest shooters prefers scope with 0.128 MOA turrets, so they can center the POI as much as possible. A 1/4 MOA or 0.1mil scope would not be able to fullfill their needs.

I will share the spreadsheet for the MV at 1000 yards a bit later today

Beiruty, Yes. You have some points, but there are so many to be made that we might swirl and confuse the beginners... A group size at distances where the trajectory is still flat, doesn't get a chance to spread vertically due to the difference in speed.

To keep the thread on track, rather than have it boil the ocean... we are talking about using a single shot velocity ladder... but then... with the question of the value of the velocity ladder when even more samples are added.

 

[Beiruty]

Beiruty, Yes. You have some points, but there are so many to be made that we might swirl and confuse the beginners... A group size at distances where the trajectory is still flat, doesn't get a chance to spread vertically due to the difference in speed.

To keep the thread on track, rather than have it boil the ocean... we are talking about using a single shot velocity ladder... but then... with the question of the value of the velocity ladder when even more samples are added.

1 single shot ladders are meanless other than finding pressure signs to detect max pressures or anomalies in the rifle bullet/barrel interface. For instance, a load which should be mid-pressure but produces clear signs of pressure.

 

[RegionRat]

1 single shot ladders are meanless other than finding pressure signs to detect max pressures or anomalies in the rifle bullet/barrel interface. For instance, a load which should be mid-pressure but produces clear signs of pressure.

And what if we could wave a magic wand and give you a budget... not a great one, but not a bad one... and your job was to take an unknown gun and unknown recipe and optimize it... aka, tune it.

Would you spend very much on a velocity test to populate more samples? Why or why not?

Would you advise beginners to focus on velocity flat spots, even given the budget to spend more than one shot per step? Why or why not? How many shots per step would it take?

And to make it easy, let us assume a general distance gun, not one for short range bench rest where we know velocity is a lower priority.

 

[Straightshooter1]

@Straightshooter1 , I was very impressed with your data. Not only with your discipline to collect and maintain your notes in such an organized fashion, but also with the results. The performance is exceptional.

I hope you don't mind me using a sample of your data to illustrate a point on the theme of prioritizing the target over the chrono. I plotted the SD versus your group size. What is shows is a R^2= 0.0592, and for those who don't speak statistics that is like saying no correlation at all.

Not to say don't use a chrono or pay attention. These data clearly show a meticulous disciplined loader at work, and a chrono is a form of Quality Control. It augments the target work, but doesn't trump it.

View attachment 1371057
Here is another example of a great performing load, giving nearly a factor of three dispersion in SD values, while keeping under 0.5 MOA.

Well done Straighshooter1.

Thanks RegionRat. I don't mind at all that you or anyone else will use the data as that's why I elected to show it as I did. The performance is better than I ever expected out of a factory RPR with a barrel upgrade.

I've used Excel ever since it first came out and always found it a very helpful tool in managing and analyzing my limited personal data of sorts. There's more to my data sheet that I posted and felt the rest might be a distraction to the point of the thread's heading. But, on second thought, I probably should have shown the whole thing; here's more of what all is on my data sheets for those who feel its needed:


, , , along with my most recent target result

 

[CharlieNC]

Shooting 2-shot charge ladders at 200yd or longer have always provided clear definition of a node on a target for me, given a suitable charge range and increment are utilized. Node defined as stable point of impact. For a number of these the velocity was simultaneously measured, and it showed no correlation to the target node; only an increasing response with noise as expected. The original premise of the Saterlee method was to reduce the number of shots required because the Chrono could be believed, while the target could not; maybe true for a shotgun but not a decent rifle. I have never shot a suitable sample size to reliably observe a velocity flat spot and doubt it's existence, while on the other hand the velocity variability does spike for odd ball circumstances such as "high" pressure loads. Irregardless the target rules as it reflects the combination of velocity and vibration harmonics.

 

[RegionRat]

The original premise of the Saterlee method was to reduce the number of shots required because the Chrono could be believed, while the target could not; maybe true for a shotgun but not a decent rifle.

I would not characterize what Scott was trying to do back then as a general method, but one where he could count on a pattern of performance from a similar match barrel to the next. But he speaks for himself so I won't try to put words in his mouth.

For a while, the concept of velocity ladders and "10 shot velocity ladders" being a way to abbreviate load development took on a life of its own. I cannot understand how that happened. It may have been the trends in chronograph proliferation and the internet/YouTube in general, but it created more swirl than it saved shot counts.

 

[CharlieNC]

I would not characterize what Scott was trying to do back then as a general method, but one where he could count on a pattern of performance from a similar match barrel to the next. But he speaks or himself so I won't try to put words in his mouth.

For a while, the concept of velocity ladders and "10 shot velocity ladders" being a way to abbreviate load development took on a life of its own. I cannot understand how that happened. I may have been the trends in chronograph proliferation and the internet/YouTube in general, but it created more swirl than it saved shot counts.

It was pushed by several in the PRS YouTube/internet crowd who appeared to spend more time trying to attract followers than shooting.

 

[wkdickinson]

Only 9 minutes long.
Not a condemnation of chronographs, but points to a greater problem with folks not understanding natural dispersion and how stats work. YMMV

I have no where near the education or practical experiences in this as you. But I decided quite a while ago that a velocity ladder is worse than useless, it's misdirecting, no matter how many shots were in each wrung. Thanks you for this explanation!

 

[Beiruty]

And what if we could wave a magic wand and give you a budget... not a great one, but not a bad one... and your job was to take an unknown gun and unknown recipe and optimize it... aka, tune it.

Would you spend very much on a velocity test to populate more samples? Why or why not?

Would you advise beginners to focus on velocity flat spots, even given the budget to spend more than one shot per step? Why or why not? How many shots per step would it take?

And to make it easy, let us assume a general distance gun, not one for short range bench rest where we know velocity is a lower priority.

All those questions and more are found and answered and tested using of hundreds of rounds in the latest Bryan Litz book. I have all his 3 books. And, the latest is a great addition to any serious shooter/reloader bookshelf.

Another full chapter was dedicated to barrel tuners.

Book Review:

Sneak Peek of Bryan Litz’s New Book: Volume III of Modern Advancements in Long Range Shooting

Bryan Litz and the team from Applied Ballistics have released another book packed with their latest...

precisionrifleblog.com

 

[Beiruty]

It was pushed by several in the PRS YouTube/internet crowd who appeared to spend more time trying to attract followers than shooting.

Exactly.

 

[Beiruty]

Thanks RegionRat. I don't mind at all that you or anyone else will use the data as that's why I elected to show it as I did. The performance is better than I ever expected out of a factory RPR with a barrel upgrade.

I've used Excel ever since it first came out and always found it a very helpful tool in managing and analyzing my limited personal data of sorts. There's more to my data sheet that I posted and felt the rest might be a distraction to the point of the thread's heading. But, on second thought, I probably should have shown the whole thing; here's more of what all is on my data sheets for those who feel its needed:

View attachment 1371115
, , , along with my most recent target result
View attachment 1371116

That is an excellent data. Kudos to you and much respect to your dedication for your data collection.
I can surely use some of those data for my semi-custom Savage PRC 6.5 loads/verification or to tune/verify GRTools powder models.

 

[darkangel_r2]

Shooting 2-shot charge ladders at 200yd or longer have always provided clear definition of a node on a target for me, given a suitable charge range and increment are utilized. Node defined as stable point of impact. For a number of these the velocity was simultaneously measured, and it showed no correlation to the target node; only an increasing response with noise as expected. The original premise of the Saterlee method was to reduce the number of shots required because the Chrono could be believed, while the target could not; maybe true for a shotgun but not a decent rifle. I have never shot a suitable sample size to reliably observe a velocity flat spot and doubt it's existence, while on the other hand the velocity variability does spike for odd ball circumstances such as "high" pressure loads. Irregardless the target rules as it reflects the combination of velocity and vibration harmonics.

Its going to depend on the quality of your rifle, equipment, and skills. Its very easy to find the true POI for a load when you're shooting a high quality rifle. Its a little harder to call the center of a 2 shot group when those two holes are an inch and a half apart at 100.

The lower the quality of your rifle, loading equipment, and skills the more shots its going to take to arrive at an optimized load simply due to the uncertainty in measurements these introduce in group shooting.

If you have a competition class rifle and you are loading it with competition class components on competition class equipment with competition class shooting skills you can then say "If the first two aren't touching the third isn't going to make it smaller."

If you're Bart and your telekinetic hole puncher's bad loads still have all the shots touching determining harmonics from a few shots per charge is probably quite reliable.

To the point about velocity flat spots. I have usually observed some charge levels produce less velocity increase per grain than others that repeats over a number of shots. in a system as dynamic as a rifle shooting I would be surprised if some fluid dynamic, thermo dynamic, or mechanical principal didn't cause some amount of variability in velocity increase per amount powder added in a way that could be repeated.

 

[CharlieNC]

Its going to depend on the quality of your rifle, equipment, and skills. Its very easy to find the true POI for a load when you're shooting a high quality rifle. Its a little harder to call the center of a 2 shot group when those two holes are an inch and a half apart at 100.

The lower the quality of your rifle, loading equipment, and skills the more shots its going to take to arrive at an optimized load simply due to the uncertainty in measurements these introduce in group shooting.

If you have a competition class rifle and you are loading it with competition class components on competition class equipment with competition class shooting skills you can then say "If the first two aren't touching the third isn't going to make it smaller."

If you're Bart and your telekinetic hole puncher's bad loads still have all the shots touching determining harmonics from a few shots per charge is probably quite reliable.

To the point about velocity flat spots. I have usually observed some charge levels produce less velocity increase per grain than others that repeats over a number of shots. in a system as dynamic as a rifle shooting I would be surprised if some fluid dynamic, thermo dynamic, or mechanical principal didn't cause some amount of variability in velocity increase per amount powder added in a way that could be repeated.

I agree a rifle and or shooter could be bad enough to generate useless data. But even my 45-70 Marlin shooting cast bullets exhibited a clear node at 50yd!!!!!

 

[PracticalTactical]

The subject of accuracy cannot be reduced to a simple concept such as chronograph confirmation.

The first problem is that we have to understand that Labradars and chronographs of the consumer grade are grossly incapable of measuring velocity to the degree we are capable of hand loading to. This leaves us to wonder if the chronograph is measuring the speed of our bullets or if we are testing the accuracy of the chronograph with our precision hand loads.

I'm not going to try and measure 0.0002" tolerance with a 0.001" dial Vernier.

As for accuracy as an indicator of speed... Yes it is but only within the limits of the base group size.

As for the base group size, I have to ask you first why do you think cheap bullets do not group as well as good match grade bullets?

If we accept that cheap bullets do not group as well as match bullets, then we must by extension of that observation conclude that bullets do not fly straight. Bullets can and do fly in more of a spiral and the size of that spiral largely contributes to the potential group size.

So we get to the tolerance stack up problem... We have bullets of hopefully high quality that hopefully fly in small spirals, coming out of a barrel that we hope is not oscillating at the time the bullet exits the bore, and with a velocity variance.

After all this, we want to reduce the final result to a measuring device that may or may not be capable of measuring within 10 FPS.

The Labradar is the best tool I have so I use it but with a grain of salt. If it tells me I have 100 FPS ES, I tend to believe it, but if it says 10 or 15, or 5, I evaluate my targets and hope for the best.