Ladder Test Help?

Discussion in 'Reloading' started by Willys46, Mar 3, 2007.

  1. Willys46

    Willys46 Well-Known Member

    Messages:
    510
    Joined:
    Oct 4, 2006
    I tried a ladder test today with new 7 RUM. I was using Retumbo starting load at 88gr working up to 94 gr by .4 at a time.
    Do you typically do this test at 300 yrds? Problem was that most the shots went into two groups with very little vertical spread. Here are the results:

    1 3024
    2 3003
    3 3004
    4 3083
    5 3085
    6 3084
    7 3107
    8 3108
    9 3153
    10 3143
    11 3182
    12 3200
    13 ####
    14 3218
    15 3270
    16 3269

    I think shot 13 did not register. I was thinking shots 4,5,6 and 12,13,14. What would you suggest?

    Thanks for your input!
     
  2. Crosseyed

    Crosseyed Member

    Messages:
    7
    Joined:
    Feb 14, 2007
    It seems to me that 300 yards is stretching it for a ladder test (just my opinion). The goal is to determine the most accurate load and I feel that at that range, there are too many other variables present. I would shoot the ladder at 100 (what I've always done), pick a load, and then take it out to 300 and see what it does. Just my opinion.
     

  3. AJ Peacock

    AJ Peacock Well-Known Member

    Messages:
    2,229
    Joined:
    Oct 7, 2005
    [ QUOTE ]

    I think shot 13 did not register. I was thinking shots 4,5,6 and 12,13,14. What would you suggest?

    Thanks for your input!

    [/ QUOTE ]

    I agree, 4,5,6 and 12,13,14 Depending on what I was wanting out of the load, I'd either try a couple groups with #5 or #13 to see if one was near what I was looking for. If you are looking for a load around 3200fps, then try 3-4 rounds each side of #13 (.1gr per step) to figure out exactly where the node is. Then pick the most consistent part of the node for your load.

    What bullet are you shooting?

    Don
     
  4. abinok

    abinok Writers Guild

    Messages:
    877
    Joined:
    Nov 25, 2004
    based only on velocities, I agree as well.

    Oh, and not only is 300 yards not "streaching it" for a ladder... its just getting warmed up!

    I shoot almost all of mine at 300, and verify at 400... even the old marlin lever gun I loaded for the other day... that will probably never be fired at hair by its owner past 100yds.
     
  5. Willys46

    Willys46 Well-Known Member

    Messages:
    510
    Joined:
    Oct 4, 2006
    Sorry I left out the details.

    7RUM Serndero, only the trigger has been touched up.
    160 Accubond.

    Thanks for the Advice, I will load some around #13. I started having stiff bolt lifts at #15 and #16.
    I will get back with results of 300yr test.

    Off to the range.
     
  6. AJ Peacock

    AJ Peacock Well-Known Member

    Messages:
    2,229
    Joined:
    Oct 7, 2005
    [ QUOTE ]
    Sorry I left out the details.

    7RUM Serndero, only the trigger has been touched up.
    160 Accubond.

    Thanks for the Advice, I will load some around #13. I started having stiff bolt lifts at #15 and #16.
    I will get back with results of 300yr test.

    Off to the range.

    [/ QUOTE ]

    Let us know how they turn out.

    Good Luck,

    Don
     
  7. Willys46

    Willys46 Well-Known Member

    Messages:
    510
    Joined:
    Oct 4, 2006
    Back From the range with mixed results. Here us the data:

    Test One FPS
    1 89 2974
    2 89.1 3093
    3 89.2 3105
    4 89.3 3130
    5 89.4 3103
    6 89.5 3125




    Test Two FPS
    1 92.6 3210
    2 92.7 3235
    3 92.8 3226
    4 92.9 3245
    5 93 3247
    6 93.1 3252

    Just for giggles I shot a 3 shot group at 300yrds with the 98.2 load. 1.16" or .38 MOA. Not that bad of group but the velocity was---3266, 3248, and 3223. Verticle was great, I misses a wind call!

    I think I might try the 93 grain load and see if the velocity spread shrinks. I thought that the velocity spread was large (43 FPS).

    Thanks for the feed back and Help
    Willys46
     
  8. CatShooter

    CatShooter Well-Known Member

    Messages:
    1,053
    Joined:
    May 8, 2001
    The tests that start this thread have a basic flaw…

    With most loads, there is a spread in velocity - say the ES is 50 fps. If we are working up a load in 0.5 grain increments, we might have a result like this...

    Averages...

    #1 = 2550
    #2 = 2575
    #3 = 2600
    #4 = 2625
    #5 = 2650
    #6 = 2675
    #7 = 2700

    OK... load #1 does NOT mean that is the mean velocity of the load. The mean velocity of the load might be 2525, or 2575. Which is it?? We can’t tell with only one round.

    If statistics are not in out favor, load #1 could be 2575 and #2 could be 2550, so it appears that load #2 is SLOWER than load #1??

    "There is a decrease!!"

    Or load #6 could be 2650, and load #7 could be 2725.
    "There has been a radical JUMP in velocities, therefore there is a radical jump in pressure, or some other irregularity"??

    The point is, you need a larger pool of samples, and 5 rounds is an absolute minimum to get an “idea” of what’s going on, and 10 rounds per load is MINIMUM to get truly accurate velocity, ES, and AV data.

    Three shot groups are adequate for getting mean velocities to run ballistic drop programs.

    One shot “groups” are not meaningful.

    In the data above…

    [ QUOTE ]
    I tried a ladder test today with new 7 RUM. I was using Retumbo starting load at 88gr working up to 94 gr by .4 at a time.
    Do you typically do this test at 300 yrds? Problem was that most the shots went into two groups with very little vertical spread. Here are the results:

    1 3024
    2 3003
    3 3004
    4 3083
    5 3085
    6 3084
    7 3107
    8 3108
    9 3153
    10 3143
    11 3182
    12 3200
    13 ####
    14 3218
    15 3270
    16 3269

    I think shot 13 did not register. I was thinking shots 4,5,6 and 12,13,14. What would you suggest?


    [/ QUOTE ]

    Now analyze the data...

    1 3024
    2 3003
    3 3004

    #2 and 3 are LOWER than #1??

    4 3083
    5 3085
    6 3084

    #4,5,6 are 80 fps Faster than #1,2,3, and are the same velocity - hello??

    7 3107
    8 3108

    # 7 and 8 are the same and only 16-ish faster than 3,4,5??

    9 3153
    10 3143

    #10 is slower than #9??

    11 3182
    12 3200
    13 ###
    14 3218

    15 3270
    16 3269

    #16 is the same as #15?? but both are 50 to 85 fps faster than 11,12,14???

    What does this tell you... by the very nature of statistics, absolutely NOTHING! This pool of data has no information other than the gun shoots bullets and they come out the front. You can NOT draw any information from one shot ladders.

    The reason is… the ES is much larger than the increments, so they overlap in both directions.

    [ QUOTE ]

    Test One FPS
    1 89 2974
    2 89.1 3093
    3 89.2 3105
    4 89.3 3130
    5 89.4 3103
    6 89.5 3125

    Test Two FPS
    1 92.6 3210
    2 92.7 3235
    3 92.8 3226
    4 92.9 3245
    5 93 3247
    6 93.1 3252

    Just for giggles I shot a 3 shot group at 300yrds with the 98.2 load. 1.16" or .38 MOA. Not that bad of group but the velocity was---3266, 3248, and 3223. Verticle was great, I misses a wind call!

    [/ QUOTE ]

    Note that the velocities are over and under the adjoining rounds.

    This is a fine example of the deficiencies of the ladder test (for velocities or group analysis).

    Nothing has been learned. If you go out and repeat the same tests, you will get totally different results… which mean that the results are meaningless.

    .
     
  9. abinok

    abinok Writers Guild

    Messages:
    877
    Joined:
    Nov 25, 2004
    and thats point of impact is so important...
    So far this week ive shot 2 ladders, with another coming on friday.
     
  10. Willys46

    Willys46 Well-Known Member

    Messages:
    510
    Joined:
    Oct 4, 2006
    Catshooter,
    I appreciate you feedback, knowledge of statistics, and scientific background. I see the problem with the string of velocities that I posted. What do you think would cause this spread? Trust me I do not want to get in a Pissing match being somewhat new to this site, but in your process of selecting a perfect load you do not account for any human error. Or I am I supposed to think that you would never miss a wind call or pull a shot. You might reject the perfect load based on human or environmental error. How scientific is that?
    We each have our ways of loading for a new gun but in the past I have wasted to much powder and bullets trying to develop a load by throwing stuff at a wall and hoping something sticks.

    I shot a 16 shot ladder. picked one load and shot .38moa at 300 yards. Without the information form the ladder I would have been wasting my time picking something out of the blue.
    Like I said thanks for your response and I will probably load multiple rounds per weight next time to get some averages. It thinks that is reasonable advice.

    AJ Peacock thanks for the direction.

    Willys46
     
  11. AJ Peacock

    AJ Peacock Well-Known Member

    Messages:
    2,229
    Joined:
    Oct 7, 2005
    Willys,

    If you are not using uniform brass, you will get velocities to go up and down on a ladder. You essentially have 2 variables in your test 1) amount of powder 2) interior size of the case.

    To eliminate the case issue, I always try to run ladders with once fired brass that has been prepped (uniformed, primer pockets, flash holes deburred etc.) and then sorted by interior capacity (brass weight).

    By using brass that is very uniform, you are eliminating one of the variables. Your velocity spread should be smaller and the nodes easier to see.

    Don
     
  12. CatShooter

    CatShooter Well-Known Member

    Messages:
    1,053
    Joined:
    May 8, 2001
    [ QUOTE ]
    Catshooter,... Without the information form the ladder I would have been wasting my time picking something out of the blue...
    Willys46

    [/ QUOTE ]

    Willys - if you are happy with the results, then you should stay with it.

    .
     
  13. Willys46

    Willys46 Well-Known Member

    Messages:
    510
    Joined:
    Oct 4, 2006
    Thanks for the responses everyone. I will keep you posted on how it comes together.

    Willys
     
  14. 300rum

    300rum Well-Known Member

    Messages:
    564
    Joined:
    Jul 27, 2006
    Hi,
    Need your help guys...
    I want to sort my cases by weight, and I have a strange situation.
    270.5gr - 3pcs
    270.8 - 10pcs
    272.0 - 8pcs
    273.2 - 9pcs
    273.0 - 3pcs
    274.5 - 4pcs
    276.0 - 3pcs
    Do you thing is a god ideea to group togheter the cases with the same grains (270.5 with 270.8), and 273.2 with 273.9
    so on ... In another words not exceding more then 0.9gr.
    I know the best groupyou can get with cases on the same weight, but I have to manny on this way.

    Thank you.
    Cris /ubbthreads/images/graemlins/ooo.gif