OAL test

Discussion in 'Reloading Forum (All Calibers)' started by Link, Jul 11, 2018.

  1. Link

    Link Silver $$ Contributor

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    Do you think this is a typical OAL test? 2 in one hole and the other out. Then at jam it comes together.
    thanks
     

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  2. Richard Coody

    Richard Coody Gold $$ Contributor

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    looks like a charge weight test to me. are you sure this is only seating depth?

    whatever looks like it is coming together. try several 5 shot groups and see if it hangs in there.
     
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  3. Dusty Stevens

    Dusty Stevens COVFEFE Gold $$ Contributor

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    Are you using wind flags?
     
  4. Curious

    Curious

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    Moving the bullet 20 thou each time is a huge amount, I would expect you to be missing nodes with big jumps like that. People do seating depth tests over a 20 thou range let alone 20 thou increments.
     
  5. Link

    Link Silver $$ Contributor

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    Berger says .040 increments with the VLDs so I figured .020 would be better. Yes 2 wind flags with a 5 mph breeze from 6 oclock. Seating depth only.
    thanks
     
  6. Puzzaz01

    Puzzaz01 Gold $$ Contributor

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    You really need to be gauging from base to the ogive. Measusuring from the base to tip can and will vary the ogive to base measurement. When you do this test you are actually moving the ogive forward and aft the lands. The oal length may all be the same length when loaded but I'll be willing to bet you the ogives are going to vary up to .005. Even the best bullets out there are not all the same length but the ogive is what matters.

    Darrin
     
  7. Link

    Link Silver $$ Contributor

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    Yes I measure from base to ogive. Is that what they refer to as COAL ?
     
  8. fatelvis

    fatelvis Silver $$ Contributor

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    No, COAL is the measurement to the tip of the bullet. CBTO is base to Ogive.
     
    Last edited: Jul 12, 2018
    Link likes this.
  9. geraldgee

    geraldgee Gold $$ Contributor

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  10. savageshooter86

    savageshooter86

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    Seating will pull them together. Test further jump in 3k increments.
     
  11. T-shooter

    T-shooter

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    When you think you're getting close, shoot at least 5 shot groups. 10 shots would confirm it.
     
  12. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    Sometimes you will be lucky to get more than about two .003" seating depth increments in a row before the groups open up again. It totally depends on the bullet, caliber, rifle, powder, etc. Berger's VLD seating depth test was set up solely to cover an extremely wide seating depth range in the event a more typical seating depth test range did not reveal anything useful. The idea is to cover a very wide seating depth range so as to find at least one (still very coarse) seating depth region where they might show some promise of tuning in. Then you can go back and test within that specific region using a much finer increment (0.003" to 0.005").

    Your test is very difficult to interpret with any certainty. For example, with only a single 3-shot group each, it is very likely that your 2710 and 2750 groups are actually indistinguishable in terms of group spread. My suggestion would be to re-test from about .010" into the lands to .025" off the lands in .005" increments to start (i.e. .010" jam, .005" jam, touching, .005" off, .010" off, .015" off, .020" off, .025" off). I have found few bullets that didn't tune in somewhere within that range. If necessary, you can always go back and cover a specific [narrower] window in .003" increments later. If you want to use 3-shot groups, I would suggest carrying out duplicate tests for comparison. Otherwise, 5-shot groups can sometimes provide a little better feel for what the changing seating depth is actually doing at the target. A good seating depth test requires good consistency from the shooter in order to be correctly interpreted. Otherwise, it can be almost impossible to tell whether it was the change in seating depth, or simply shooter error that actually changed the group size/shape/POI on the target.

    FWIW - seating bullets into the lands can create pressure spikes as the bullet is more resistant to movement initially. Likewise, seating bullets .030"-.040" or more farther off the lands with a set charge weight can start to increase pressure as the bullet is seated deeper in the case and usable case volume decreases. Over-pressure should always be a consideration when seating bullets deeper in the case by large increments (i.e. more than .030"-.040" or so), or when seating bullets into the lands. However, unless your selected charge weight is already yielding close to MAX pressure with a bullet seated at around .010" off the lands, you can likely safely move it over the range I suggested above without too much concern.

    Lastly, although it is not always written in stone, commonly-used bullets often show similar optimal seating depth trends between different rifles and even shooters. For example, 185 Juggernauts will generally tune in somewhere between .015" and .030" off the lands in a wide range of different rifles and loads. So if you're using a bullet commonly used by a lot of shooters, asking what seating depth others are successfully using may be a relatively easy way to find a good starting point for your testing. If so, it may save you from having to cover such a wide seating depth window that it forces you to use really large (.020" to .040") increments the first time through.
     
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  13. OmegaRed

    OmegaRed Silver $$ Contributor

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  14. mikecr

    mikecr

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    The shooter here made the common mistake of seating testing -from a powder node. All he accomplished there was collapsing of the powder node, and nothing w/regard to finding best seating.
    If you're going to do Berger's recommended seating testing, at least read & follow it.
     

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