ladder test? does it work

Discussion in 'Reloading' started by britz, Mar 20, 2007.

  1. britz

    britz Well-Known Member

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  2. AJ Peacock

    AJ Peacock Well-Known Member

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    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
     

  3. CatShooter

    CatShooter Well-Known Member

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    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.

    .
     
  4. AJ Peacock

    AJ Peacock Well-Known Member

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

    [ 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
     
  5. AJ Peacock

    AJ Peacock Well-Known Member

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    [ 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
     
  6. CatShooter

    CatShooter Well-Known Member

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    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.

    .
     
  7. Guest

    Guest Guest

    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
     
  8. Mikecr

    Mikecr Well-Known Member

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    I agree JPretle. The ladder isn't for finding the best grouping, or even best load. It's for finding stable load areas. I watch ES as well as grouping.
    Then group shooting with variance in a stable area for best grouping. Then seating depth, and neck tension adjustments can be made for better grouping still.

    After a standard 30rd 300yd Ladder, I normally shoot 3rds each around the best areas for confirmation. I use a cheap video camera from radio shack to record the shots, and an Oehler w/20'screen spacing.

    I can say it doesn't work well for every barrel. And every imaginable factor needs to be held constant during testing under best conditions. Including barrel temp.
    But if anything, you'll usually see loads to avoid for sure. I've seen some crazy flyers while moving up in load. I've seen high velocity shots hit way low, and low ES areas with alot of horizontal for some reason. Drawn figure 8s with one barrel.
    A latest barrel tested using a ladder simply walked up the paper with each shot touching the previous. No hope of determining anything from it in this case. So I'm always lookin for the next good method.
     
  9. BountyHunter

    BountyHunter Writers Guild

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    Catshooter

    I have no idea where you got the idea that if a barrel did not vibrate "someone" said that it would shoot little groups. I have never seen that said anywhere about a ladder.

    Just where and who said that?

    Your disagreements are based on wild assumptions and assumes that the shooter does not apply a modicum of common sense.

    For example the vibration thing and the 1 1/4 MOA refer with POI shift.

    First off IF my gun will only shoot 1 1/4" groups, forget the ladder. Hell, forget any technique because they all do not work equally well!

    IF you are shooting 1 1/4" guns, then buy a $10 hand lee loader and plastic dippers and slap em together. Doubt you will do any worse. Just slap something together that does not blow up the gun.

    You have to have a gun capable of shootin at least .5MOA or you are correct you cannot tell anything. but surprise surprise, that is with any technique. You have to shoot in no wind conditions, you have to be capable of shooting tight groups. You have to understand enough about reloading, ie what probably will work or not to be able to put together reasonably accurate ladder loads to test. If you cannot do all that, then Federal Premium factory is the answer.

    You can and will change the barrel harmonics with any change of components and there is no magic MV area.

    I have never seen a match grade gun that could not use the ladder to extremely quickly and accurately put together a top notch load.

    When my guns shoot sub 1" groups at 300 or 400 with the initial ladder loads, the technique works. Fine tuning the seathing depth and neck tension will normally take them down much further.

    I have taken guns from the gunsmith shop after building, broke in one night, initial ladder the next (did not have time for neck tension and seating depth workup) and then went to match the next day and won state championships.

    IF you have a accurate gun and can shoot, then the ladder along with a decent chrono will give a very accurate load IF that combo of components is capable of it.

    BH
     
  10. CatShooter

    CatShooter Well-Known Member

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    [ QUOTE ]
    First off IF my gun will only shoot 1 1/4" groups, forget the ladder. Hell, forget any technique because they all do not work equally well!

    IF you are shooting 1 1/4" guns, then buy a $10 hand lee loader and plastic dippers and slap em together. Doubt you will do any worse. Just slap something together that does not blow up the gun.

    [/ QUOTE ]

    I never stated a range for that 1-1/4" group - calm down, you are loosing it.

    Then I can assume that we disagree???

    .
     
  11. royinidaho

    royinidaho Writers Guild

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    The Ladder Test works for me. It takes a bit to get to understand what's going on as the test is so much different than what I am used to (load 3 shoot 3, try something other powder weights then load 3 and shoot 3, again and again and again.

    When I do the shoot 3 thing I end up getting things to shoot really well. Problems are takes lotsa powder and bullets. The bigger problem is that I end up with a load that shoots super under only the 'specific' conditions under which the load was developed. Variations in temp/season etc, different powder lots and who knows what else caused the groups to fall off drastically.

    With the ladder test, I have found that, the variables have much less affect.

    FWIW.
     
  12. 1kstr

    1kstr Well-Known Member

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    I am going to give the ladder test a test. Once the weather around this WC Minnesota lakes country settles down
    and warms up a tad. The wind has been blowing for three days. Range time soon however. Have a couple guns I need to develop loads for. This will be different than the way I am used to as well. Will post my results later.
    1kstr
     
  13. milanuk

    milanuk Well-Known Member

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    'Calm down'?!? From what I can see, you're the one who gets on a soap box ranting and raving every time anyone even mentions the words 'ladder test'. It's like an open sore with you... you just have to keep pickin' at it.

    For what it's worth... I do agree with you on a few points. The classic ladder test makes some assumptions about the shooter and his gear (as far as capabilities, etc.) that may not be true for everyone. It tends to ignore certain things such as barrel heating/fouling (something Dan Newberry's OCW method attempts to redress). And finally, it makes huge assumptions about the tendency of a given gun/load to behave in a predictable way as far as nodes, going so far as to trust one round per increment as an indicator of that gun/load's behavior. Statistically, a sample size of one is pretty unsound, no doubt about it.

    All that aside... the method works. Not for everybody, and not with every gun, but it usually works. Given a reasonable idea of where to look, a shooter can find a sweet spot in relatively short order, fine tune the load, and be about their business, whether that be practicing or hunting or competing, in fairly short order. If a person is really concerned about statistical sample size... once you have what looks like a winner of a load, *then* go thru and load up 10 or 20 and verify that it performs the way you want. That's just plain common sense no matter how you find the load in the first place.

    Anywho, sorry about the counter-rant, but I just get vexed watching someone try to convince the world that something shouldn't work... when it usually <u>does</u>.
     
  14. AJ Peacock

    AJ Peacock Well-Known Member

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    [ QUOTE ]


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



    [/ QUOTE ]

    OK, you said it was vibration. Functionally equivalent for a discussion like this.
    [ QUOTE ]


    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.


    [/ QUOTE ]

    Funny you should mention that, as I have a degree in Applied Mathematics and Computer Science. A Ladder test is not a single data point. It is a series of experiments that give data points across the range of its independent variable (powder charge).

    If I run a ladder test and vary the loads by .3 grains, its no different than if I run the test and vary them by .1 grains or maybe .005 grains. When I run a ladder test, I'm not looking 'INITIALLY' for the best load. I am looking for an area to use for 'FURTHER' investigation. I believe a ladder test is an excellent process for THAT! With the fewest number of shots.

    That further investigation may be a more granular ladder test of .1gr increments to verify the original test and put a little finer point on my understanding of the results.

    Note the following chart. The first chart is the Vertical spread for an entire Ladder test for a 7mm Rem Mag using RL-22 powder. I had borrowed a 1/2 lb to see how it shot. I liked the node around shot #19. So I purchased 10lbs of RL-22 and decided before I really honed in on a load, I'd rerun that portion of the test to eliminate lot to lot variation with the powder. I loaded (using the new lot of powder) loads 15-21. The second chart are those loads.

    [​IMG]

    You might notice that the general shape of the 2 tests are very similar (not EXACT). But the SAME node can clearly be seen between the 2 tests. The y axis is the 3 shot total vertical spread in MOA from the point of aim. The load I chose was actually .1gr higher than load #19/#5.

    Verifying the load with groups, they have all been under .5MOA (3 shot groups), not bad for a rifle that weighs less than 8 pounds. I found this load with a powder I had NEVER used before in a total of 36 shots (including 3 foulers before each test). I then verified with 3 3shot groups at my chosen load, so a total of 45 shots and I have a load that is 3000fps, 162gr bullet typical group size of .4MOA at 200yds.

    [ QUOTE ]


    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.

    .

    [/ QUOTE ]

    Well, the above ladders were shot with a factory 24" Remington barrel in a 700 action. I've bedded the action in a Brown precision Kevlar/foam stock and swapped in a Timney trigger, but the barrel/chamber are factory.

    Oh, this rifle isn't much different accuracy wise from any of my other Model 700's. Maybe I am just REALLY lucky???


    Later,
    Don