chicken or egg - seating depth or powder

Discussion in 'Reloading' started by datsjeep, May 24, 2010.

  1. datsjeep

    datsjeep Active Member

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    So what comes first? If trying to develope a load and your limited to mag length do you first start with different grains of powder, find the most accurate regardless of group and start adjusting the seating depth or do you switch powders to try and find a more accurate powder.

    If you know the seating depth of an accurate load i.e. factory load should you duplicate that depth, find an equally accurate powder combo then slowly extend seating depth.

    It just seems with all the different factors you could shoot your barrel out before finding an accurate load.
     
  2. moombaskier

    moombaskier Well-Known Member

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    What caliber and what bullet are you wanting to start with? Maybe I can help save you some time.
     

  3. Len Backus

    Len Backus Administrator Staff Member

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    Powder first, OAL second.
     
  4. datsjeep

    datsjeep Active Member

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    270wsm in a tikka T3 150 Berger

    My OAL measures 2.405 to the lands. To fit in the magazine I have to seat to max of 2.340 giving a coal of 2.895 where mag max is 2.900. This creates a jump of .065.

    Most accurate load I have found so far is the factory federal premiums with an OAL of 2.238 and jump of .167 but produced 1 ragged hole at 100yds.

    I have tested h1000 & rl22 at the OAL of 2.340 with poor results.

    I was thinking about loading 3 rounds each of Retumbo 69-70.5 in .5 increments at the OAL of 2.240 (matching factory federal) 2.290 (half the distance) 2.340 (max mag COAL)

    But I am not sure if this is a good approach.
     
  5. 223Rem

    223Rem Active Member

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    How can you find the most accurate powder without regarding the group size?

    Different weight bullets work better with different powders.

    The bullet design (ogive type) also plays a factor when you consider the amount of leade in the barrel's throat and wanting to keep the COAL mag length. If the barrel likes a particular bullet with a Secant ogive and only a slight jump to the lands, there is a very good chance the COAL will no long be mag length.
     
  6. datsjeep

    datsjeep Active Member

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    You can't find the most accurate load without regarding group size. I don't understand what your asking.

    IS it not true that a gun may appear to NOT like a bullet powder combo at 1 OAL but like that same combo at a different OAL?
     
  7. boomtube

    boomtube Well-Known Member

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    IF the load is no good, changing the seating won't make it so.
     
  8. datsjeep

    datsjeep Active Member

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    Ok I guess I will just load them all to max mag length from 67 to 71.5 in .5 grain increments and see what happens
     
  9. Gunpoor

    Gunpoor Well-Known Member

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    You have half the work done for you! Use FC headstamp brass of one lot and the same bullet that is annotated on the end of the box of factory loaded Federal Premiums and seat the bullets to the same COAL and pick a suitable burn rate powder and start charging at the near bottom of the Min load and work up in .5 grain increments until you are loading the Max recommends charge weight. You can load one of each charge weight for a mid-range ladder test (300 to 500 yds) or load 3 or 4 at each charge weight and shoot for groups. Shoot the lowest charge weight first and then the next lowest and so on and so forth while examining each fired case looking for signs of excessive pressure. If none of this ammo shoots to your satisfaction leave the seater die set where it is and try another powder until you start seeing good results. You may have to clean the bore of your rifle periodically, depending how many rounds you fire and the nature of the rifle itself. I have rifles that you can shoot many rounds without noticeable accaracy loss and I have one hardhead that will shoot with amazing accuracy until the barrel copper fouls ( which is quite quickly). After you find some suitable accuracy then you can fine tune the powder charge or fine tune the COAL, but only make one change at a time so you can analyze the results and hopefully make sense of it.
     
  10. MagnumManiac

    MagnumManiac Well-Known Member

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    I can tell you my method.

    I select the powder that gives the highest velocity in several manuals, load 4 strings working backwards from the max load and load 5 rounds of each, I then shoot for groups at a COL just shy of max mag length; .005"-.010". In magnums and standard cases like the 06's, I work up in 1gr increments, smaller cases I use .5gr increments, and really small cases in the Hornet family I use .2gr increments.

    Once I have found the most accurate powder charge, I then go to the ladder test and load 1gr above and below that charge in .3gr increments. I then shoot them in a round robin to determine where the accuracy node is.

    Once that has been determined, I then load 5 rounds at DECREASING COL's in .005" increments and see if I hit the sweet spot at a shorter than max mag length COL.
    It's surprising that some hunting rifles shoot best when the bullet has a jump of .100" or more, and others prefer .005"-.010".
     
  11. datsjeep

    datsjeep Active Member

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    I don't have any federal brass and I really don't want to shoot Nosler partitions. If I did I would just shoot the factory loads.

    I do agree with what your stating about half the work being done and I could load with a COAL to match the factory load if thats recommended but it would create quite the jump, .167 to be exact.
     
  12. datsjeep

    datsjeep Active Member

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    Ok Magnum if I understand you correctly. You start with a COL of magazine length - .005. Retumbo seems to have the highest velocity listed with 71 grains being the max. So I would load 5 shots each of 68,69,70,71

    After that is where you lost me. Assuming 69 grains is the most accurate you would load 1 each between 68 & 70 in .3 grain increments and shoot them in a round robin (?) to determine where the accuracy node is ????? I dont get it.

    Then you would reduce the seating depth by .005 to find a sweet spot on COL. Assuming the sweetspot on my gun is somwhere close to the federal premiums I have shot accurately, moving my COL by .005 and 5 shots each would take me 103 rounds.
     
  13. J E Custom

    J E Custom Well-Known Member

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    I wouldn't try to duplicate factory loads because they often use proprietary powders that we
    cant buy.

    I approach a starting load this way= Make a dummy round that will clear your mag by .020
    in length and keep it with your dies for future reference.

    Next take the same type and weight bullet and place it beside the dummy round to see how
    much it infringes on the case capacity.

    Try to find a powder that @ 98% case density reaches near maximum pressure. this will
    normally tell you which powder will reach max velocity and pressure for that round.

    Then start loading 1 to 2 grains below max and work up in .02 grain increments.

    I chronograph all of my test loads looking for the best SDs with that powder, primer,bullet
    and case combination. (SDs are very important for long range shooting/hunting).

    Once you have the best SDs then you can play with bullet designs for optumum accuracy.

    I find that most loads perform best at near 100% powder capacity

    This process saves a lot of trial and error for me.

    Just the way I do it because it works for me.

    J E CUSTOM
     
  14. MagnumManiac

    MagnumManiac Well-Known Member

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    I load a total of 25 rounds @ -.005", -.010", -.015", -.020" and -.025" from the mag max length minus the initial .005"-.010". That's it.
    Presuming your sweet spot is the same as any factory ammo is erroneous, it may be but most likely will be something completely different.
    The sweet spot is generally somewhere very close to the lands or even into the lands, and then there is a second spot further from the lands that it will be in. What it is is where the barrel harmonics are in tune with the bullet barrel time.
    The OCW method is, assuming your load is 69gr's, you would load 5 @ 68.3gr, 68.6gr and 68.9gr, then you would load 5 @ 69.3gr, 69.6gr and 69.9gr, presuming you're not working with a max load of course! I shoot these randomly at the same aiming point to determine which loads shoot nearest to the centre of the group, this way helps to eliminate any 'vertical' at longer ranges, this also known as the 'accuracy node', it may be that even a 2gr spread may shoot to the same POI, which is the Optimum Charge Weight for that bullet/powder combo. (If you're not comfortable shooting them randomly, shoot as groups as you normally would in strings.)
    You then work with the most accurate of these, or the ones that print to the centre of the aiming point, those that are high or low are discarded from further testing. This test should be performed at 200yrds (min) or further for best results.
    In other words, a charge that is 69gr for instance may be completely stable even if there is a variation of +/- 1gr from the desired charge of 69gr's. This doesn't happen too often, a variation of 3% is typical, which equates to about +/- .5gr in most large capacity cases.

    If anyone can add anything I might have missed, please do so.