Understanding ladder test results

[Ray P]

Yep' all good until the power goes out or you don't have an APP to calculate for you.

That's why I have a 35 y.o. Schaums guide for statistics, an HP 48GX with stat pac, and a circular slide rule on hand. Ya never know.

 

[Ray P]

Yesterday was kinda lost due to numerous things, but I greatly appreciate the insights and advice, Varminterror, South Prairie Jim, AJC1, et al.
And I recognize now I was not using the Slatterlee method. Closest thing to what I was trying to do is shown here:

https://www.loaddevelopment.com/load-development-ladder-test-method/

I will re-shoot the ladder with three loads each at 0.2 grain increments; mostly to see if I can eliminate/minimize errors in my process from the first attempt. Probably won't happen until this coming weekend, wind permitting. That should validate or disprove those two flat spots, and maybe pick up a third at the top end.

Which raises a question: If the RCBS Chargemaster throws charges accurate to +/- ).1 grain, and given the mechanical nature of the final trickle process, wouldn't it follow that the charges thrown follow a normal bell curve distribution centered on the target charge?

 

[Varminterror]

@Ray P - that link describes a combination of Satterlee method and an Audette Ladder method. The POI analysis on target is the Creighton Audette Ladder, the velocity curve analysis the Scot Satterlee method. The Ladder method alone does not analyze velocity in the way that article describes (in other words, doesn’t at all), but it has become exceptionally common for folks to stack the Satterlee method together with either the OCW method or the Ladder method.

As I stated above, with nearly perfect reliability, I’ve witnessed a congruence between the Satterlee method and the Audette Ladder (and the Dan Newberry OCW method, also mentioned in the article). The example provided in the article reflects that congruence.

 

[Varminterror]

If the RCBS Chargemaster throws charges accurate to +/- ).1 grain, and given the mechanical nature of the final trickle process, wouldn't it follow that the charges thrown follow a normal bell curve distribution centered on the target charge?

No. Because the final trickle is not a “mechanical nature.” The final trickle is controlled by digital signal from the electromagnetic load. We pray the coil behavior is linear, which might offer a normal distribution, but frankly, considering the ~$300 common purchase price of these devices, we can’t pretend the componentry are high performance, precision instruments.

 

[dcloco]

Satterlee adds chrono data to the mix. The output of the chrono displays the velocity. Holes in the paper indicate what the barrel likes.

This is the same as the modified Audette load workup. Ten rounds and done.


My point about this is, YOU DON"T NEED a chrono to tell you what the barrel likes with a particular bullet/powder/primer/case combination. (barrel harmonics)


Several of you keep pointing out, takes the accuracy ability of the person out of the equation. True. BUT........if the person cannot shoot accurately, what is the point of spending money on a chronograph, and, and, and.

Get off the computer, load ten rounds, to the BEST of your ability, and punch some paper at 300 yards.

Bring a friend to watch YOU when you shoot (not the paper, the paper is the truth teller). Have the spotter VIDEO you. Use a short bipod and a rear sandbag.

 

[JFrank]

There's also the Montana method, especially handy for those without or do not have access to electronic devices.

 

[Walkalong]

My point about this is, YOU DON"T NEED a chrono to tell you what the barrel likes with a particular bullet/powder/primer/case combination. (barrel harmonics)

No, but if your target is a load for PRS, it is critical that you know the velocity at not only that temp, but other temps as well. Shooting a known distance all the time? Not so much, get it close, walk it on target, fine tune, have fun.

 

[Varminterror]

My contention after using these methods for thousands of loads in hundreds of rifles over the last 25 years is that the Audette ladder is like listening with a stethoscope to hear “what the barrel likes.” Whereas, with the Satterlee method, the barrel is screaming what it likes at you with a bullhorn. It’s almost too easy.

 

[JFrank]

Yesterday was kinda lost due to numerous things, but I greatly appreciate the insights and advice, Varminterror, South Prairie Jim, AJC1, et al.
And I recognize now I was not using the Slatterlee method. Closest thing to what I was trying to do is shown here:

https://www.loaddevelopment.com/load-development-ladder-test-method/

I will re-shoot the ladder with three loads each at 0.2 grain increments; mostly to see if I can eliminate/minimize errors in my process from the first attempt. Probably won't happen until this coming weekend, wind permitting. That should validate or disprove those two flat spots, and maybe pick up a third at the top end.

Which raises a question: If the RCBS Chargemaster throws charges accurate to +/- ).1 grain, and given the mechanical nature of the final trickle process, wouldn't it follow that the charges thrown follow a normal bell curve distribution centered on the target charge?

You'll do fine with the chargemaster

 

[Howa 9700]

Having never hear of Satterly or any of the other ladders, I did some reading. What I found interesting was what Satterly said was the purpose. It was to find the best velocity to match up the bullet to the barrel's harmonics. He had done tests with same bullet and same gun and as many as 10 plus different powders (and named them), and while the powder charges were all different, the magic spot for each always had the bullet running down the pipe at the same velocity.....and hopefully at a velocity near max pressure. Regardless of powder or powder charge, magic spot showed up at same velocity.

After that it was to fine tune seating depth. Once you got those two paired up, dead nuts accurate.

Have always thought this must be a chicken or the egg thing......trying to work out two highly dependent variables....powder charge and seating depth) at the same time. Which one to fix first. Satterly thingy seems to solve that riddle.

 

[Varminterror]

Have always thought this must be a chicken or the egg thing......trying to work out two highly dependent variables....powder charge and seating depth) at the same time. Which one to fix first.

Charge weight is a much larger knob than seating depth. With many bullets, HUGE spans of seating depth will shoot incredibly small, whereas charge weight is far more critical. I believe I shared above, but if not in this thread, I know I have recently - I have let my throats erode from 5 thou jump to greater than 140thou jump without chasing or adjusting and delivered relatively consistent precision across that span... I’ve also completely neglected any seating depth tuning at all in my PRS match rifle for the last 3 seasons, for that reason (knowing the throat will erode quickly and that I don’t need to chase it). Alternatively, I confirm my charge weight node before every match, and I have simply done exclusively that powder charge load development.

Admittedly, I’m not entirely convinced these tests are confirming a “velocity node.” A lot of guys talk about magic velocities for given bullets, but I also watched a barrel bleed velocity like a falling meteor, but the nodes remained correlated to the charge weight, despite dramatic changes in velocity. But frankly, it doesn’t really matter - the node is where it is, and the paths to find it are what they are, so I trust what the barrels tell me.

 

[JFrank]

No, but if your target is a load for PRS, it is critical that you know the velocity at not only that temp, but other temps as well. Shooting a known distance all the time? Not so much, get it close, walk it on target, fine tune, have fun.

Well said.
J