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ladder test? does it work

 
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  #1  
Old 03-20-2007, 09:11 AM
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ladder test? does it work

I just read the article on Ladder test theory and I was wondering if anyone has done this and if it works. here is a link to the site.
http://home.snafu.de/l.moeller/Engli...tm#LaddertestI am considering doing this, but I am very sceptical of the science behind his theory. I would appreciate you input.
Britz
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Old 03-20-2007, 09:26 AM
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Re: ladder test? does it work

It works for some and it doesn't work for others. You will find those that vehemently disagree with the approach.

I personally have had good luck with it. I think it boils down to your particular situation. I don't think running a ladder test with mixed brass at short range will do anything but get your barrel dirty. On the other hand, my personal opinion is that if you use consistent high quality brass and shoot at a long enough range (shooting over a chronograph), you can learn a lot.

I like to graph the velocities as well as the vertical spreads for my ladder tests. When I see a point where the vertical spreads and velocity spreads coincide, I will then look around there for my load.

Your mileage may vary.

Search for Ladder in the subject over the last few months and you will find several posts on the subject.

Don
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Old 03-20-2007, 09:46 AM
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Re: ladder test? does it work

I am not a supporter of this "theory", as it has too many flaws in it. Some say they have found good loads with it, but even a blind pig finds an acorn or two.

The "theory" is based on the idea that shooting errors are due to vibrations in the barrels, like a pendulum, and if you can find one end of the swing, the rifle will be more accurate, because minor variations in velocity will have less effect at one end of the sweep, than if the chosen load is in the middle of the sweep.

Sounds good on paper, but there are a lotta holes in it.

The first is that it assumes that barrel whip is the only cause of large groups... and that is NOT true.

If a load of powder "A" gives tiny groups at 3,200 fps... the same velocity with powder "B" might give humongous groups. So that fact right there kills the harmonic, or node theory. While thin barrels can show vibration patterns, they effect of the vibrations are often smaller that the size of the groups caused by other factors... and stable barrels of quality will often show small groups at many velocities, and each increase in powder will cause the group to climb up a bit, so you will have a string of small groups with each one a bit higher than the previous... and in the 5 or 10 groups, you may find one that is better... or maybe all with be so close that you pick the one that meets your needs.

But the real problem with ladders is this. With a average barrel that shoots (say) 1-1/4" groups, any shot can statistically fall in a circle of 1-1/4". If we increase the load by 1/2 grain, we have an increase in velocity, but any of the shots of the second load can fall into a circle 1-1/4" circle, (AND THE CIRCLES OVERLAP)... and so on for five variables with a load spread of 2.5 grains.

So with just these five load variables we can shoot a ladder. So, from the Point of aim:

The first shot can be 5/8" high, or 5/8" below the poi.
The "center" of the second shot will be a bit higher because of the increase in velocity, but from that new base, the second shot can be 5/8" high, or 5/8" below the "new center"... and so on.

Now... as velocity increases, the center on impact of a "group will be higher, but in that group, each individual shot can be 5/8" below, or 5/8" higher.

To bring this to a more logical example... if we took two of the cases that are 1/2 grain apart, and repeatedly shot the two, we would find that each pair would vare and the second shot could be either above or BELOW the first shot... and each pair would vary by as much as an inch.

To make this make more sense now... take a bunch of cases that have been match prepped (weighed, etc). Break the bunch into groups of 5 cases, and then vary the load by 1/2 grain, so you wind up with five sets of five cases.

Now shoot the first five as a ladder on one target.
Then with a new target, do the same with the second group.
Then do the same with the other three sets.

When you wind up with is five targets with five "ladders".

Now... here's the killer. If you lay the targets out on a desk, none of the targets will resemble the others.

If you give the five targets to a "ladder believer", and tell him that they come from five different rifles, and ask him to "analyze" the targets, you will get five different "best loads" for the five targets... which says that there is no information in the ladders, because if there was, then a separate analysis of each target would give the same load as best, IF the ladder theory works.

Don't take my word for it... do it, and see for yourself.

.
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Old 03-20-2007, 10:13 AM
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Re: ladder test? does it work

Hi CS, I figured it wouldn't take you too long to show up on this thread [img]/ubbthreads/images/graemlins/wink.gif[/img]

[ QUOTE ]
I
If a load of powder "A" gives tiny groups at 3,200 fps... the same velocity with powder "B" might give humongous groups. So that fact right there kills the harmonic, or node theory.

[/ QUOTE ]

Not exactly, since different powders can have VASTLY different pressure curves the harmonics would be HUGELY different between the powders. I don't think ANYONE is claiming that a load with powder A will then translate to a load with powder B. That is just plain silly. I can get the same velocity using vastly different powders and they won't shoot even close to the same place (IMR 4350 and H50BMG for example).

CS, point out where someone of note is claiming that different powders at the same velocity will give the same type groups with different powders (talking small groups here, sub 1/2MOA, as anything larger than that really doesn't matter). Just post a link and I'll take a look.

For the initial poster, here is a link to a discussion on barrel harmonics FWIW.
http://www.rifle-accuracy.com/harmonics.htm

Nice day gentlemen,

Don
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Old 03-20-2007, 10:19 AM
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Re: ladder test? does it work

[ QUOTE ]
I am not a supporter of this "theory", as it has too many flaws in it. ...

The "theory" is based on the idea that shooting errors are due to vibrations in the barrels, ...

[/ QUOTE ]

CS, what is YOUR "theory" of why a load x shoots great and a load x+.5gr or load x-.5gr wont shoot worth beans?

If its not Harmonics, what is it? Enlighten me please.

Thanks,
Don
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  #6  
Old 03-20-2007, 10:54 AM
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Re: ladder test? does it work

Don...

You missed something.

I didn't say it wasn't harmonics - never said that!!

But the assumption in Ladder theory is that if a barrel didn't vibrate, all bullets would fall in a teeny group, so if you can isolate the "node" then you too can have teeny groups. But it IS possible to completely eliminate vibration, and it does NOT guarantee teeny groups with average to mediocre barrels.

And the same problem happens at the other extreme. If you have a bench rest grade barrel, and you run ladders, you get a target with a string of nearly evenly spaced holes from bottom to top, with no indication AT ALL, which load does what... and I had that happen this past November with a .264WM... running two shot test groups (would fit the ladder definition), each pair was touching, and just a bit higher than the last... so the only information I got was what the max load was, and I have to start all over again.

What I was pointing out is... that statistically, one shot at each load is not enough information to draw a conclusion, because each load has such a large spread. With good barrels, even two shots are not enough data to draw a conclusion from.

In any science, an experiment MUST have a large enough sample of EACH item to assure that the data is representative of that item.

So one shot of a load that can shoot a 1-1/4" group is meaningless, because if you repeat five ladders of the same group of loads, each of the five ladder targets will give you a different "best" load.

Any math major can give you the math laws that define this, so this is NOT my theory or opinion... a mathematician would wet his pants laughing at the "Ladder theory". The sample pool is just not large enough to give you accurate information to draw from.

Put another way... if I shot ten targets with two 30 calibre rifles... so it could be 3 from one, and 7 from the other... or 5 from one and 5 from the other... you could NOT tell me which were "the best" loads for them... and if you can't do that, then your data pool is way too small.

If the ladder test had meaning, which load was the best, AND you would be able to say which 5 targets were from the same rifle, because the data would replicate on each target... which it does NOT.

And all that assumes an accurate barrel... factory barrels can be so poor that they just can't shoot small or predictable groups, so with ladder theory, you can chase your tail for weeks and never find anything.

.
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  #7  
Old 03-20-2007, 10:55 AM
 
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Re: ladder test? does it work

Britz, it works for me. The big advantage is that one can have a variance in the powder charge by as much as .2g or sometimes more, and you will still be in the node. I shoot my ladder test at 300yds. Many times, I will have 4,5 or even 6 shots in 1/2', or even less. (IE,.223 with powder charge in .2g increments) The idea is to select a charge wt that falls in the middle of the node, and if you are +or- on the powder charge, your rounds will still fall in the node. FWIW Jim
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