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bullet selection and reloading pressures

Discussion in 'Handloading and Reloading' started by JCSC, Aug 12, 2019.

  1. JCSC

    JCSC Member

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    I am not having any issues, but curious on some experienced thoughts on what causes noticable pressure changes.

    Here is a scenario and some thoughts I have, relating to reloading 9 mm.

    Lets say that I am currently using "x" bullet. With all bullets, I tend to save one in small plastic ziplock and blueprint the bullet to some extent. length, weight, etc.

    Once I have an established load, this allows me to calculate the internal axial depth from the bottom of the seated bullet, to the internal face of the casing, thus giving me a known internal volume.

    Let's say that I chose to switch from a Hornady 124gr HP to a Berrys 124gr FP. If I am conscious about insuring I maintain the same internal volume, (provided the subsequent OAL is allowable), can I assume that I would see similar safe pressure situations across both projectiles, or any others for that matter, provided they have a flat base.

    I could be way off line, but my thought was that if I maintain a consistent internal volume, regardless of bullet, I should see no changes, other than additional pressure from a bullet weight change or change in rifling / bearing contact surface.

    Does the bullet / rifling amount of contact alter internal pressure significantly?

    I would never shortcut my reloading practices, or not refer to manuals. I only load for about 6 calibers, but for interchanging pistol bullets, I am curious if my thoughts are sound.
     
  2. kcofohio
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    kcofohio Contributing Member

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    Case volume from one brand of case to another is something to take into consideration. It may not change pressure much, but I would feel better stepping down a bit, just in case of an unseen element.
     
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  3. Blue68f100

    Blue68f100 Member

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    That does not necessarily work due to bullet construction. Most use a different harness core which can increase/decrease friction going down the more. Then there is how much of the bullet is ridding the bore. Always best to back of a little and work back up. Then you have the ogive to deal with. Different brands/types require a different OAL at times too. The OAL that fits one may not work with a different bullet.
     
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  4. Texas10mm

    Texas10mm Member

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    Bullet construction has a big impact on pressure.

    A lead bullet load may well leave a jacketed bullet stuck in the bore and jacketed load can be way to hot for lead bullets.
     
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  5. JCSC

    JCSC Member

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    Thanks! Just something I had wondered. Now I just need to consolidate my two pistols into one powder.
     
  6. LiveLife

    LiveLife Member

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    When loading for multiple pistols, I first determine the longest "Working OAL" that will work in both pistols/barrels/magazines and then conduct full powder work up to identify the most accurate powder charge (after reliable slide cycling and spent case extraction/ejection).

    If I want to squeeze out even greater accuracy, I will incrementally decrease the OAL (say be .005") to see if group size decreases.

    What you are trying to do is what we have been doing with bullet seating depth in practice using OAL/COL to maintain comparable chamber pressures.

    While I sort .308 brass by internal case volume to separate thicker military vs thinner commercial brass, I do not worry about sorting pistol brass by internal case volume.

    While different headstamp brass presents with slightly varying amount of internal case volume (which can affect chamber pressures), this is overshadowed by other reloading variables like neck tension, etc.

    So many reloaders do things like for "typical" 115 gr FMJ/RN bullet, use 1.130" OAL and same powder charge or for 124 gr FMJ/RN, use 1.135" OAL.

    I also always check the sufficiency of my neck tension to prevent bullet setback by measuring OAL before and after feeding/chambering dummy rounds from the magazine and releasing the slide without riding it as it doesn't matter what your "finished OAL" rather "Chambered OAL" that dictate the actual chamber pressures. ;)

    Another safeguard we use, especially is you are using mixed range brass with unknown reload history and condition of brass is to not use max published charges. By using high-to-near max charge instead, this gives us some buffer in case of internal volume variance, bullet length variance, finished OAL variance and any bullet setback as case wall thickness vary by headstamp.
     
    Last edited: Aug 12, 2019
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  7. Dudedog
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    Dudedog Contributing Member

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    As mentioned earlier bullet shape and construction matters.
    Midrange loads you are probably ok to swap the bullet, anything close to MAX I would work up again.
     
  8. JCSC

    JCSC Member

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    Thanks for all the responses.
     
  9. murf

    murf Member

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    general rule: when changing components, drop the powder charge 10 percent (less with some powders like h110), and work up.

    luck,

    murf
     
  10. bullseye308

    bullseye308 Member

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    Difference in bullet materials makes a slight difference as does diameter. Some 9mm bullets can be .355, .356, .357, or .358. Cast lead, coated, plated, jacketed, or solid copper could all change things up a little.
     
  11. Texas10mm

    Texas10mm Member

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    Lyman found that diameter had little effect on pressure when it comes to cast bullets.
     
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  12. forrest r

    forrest r Member

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    quick loads will give you an idea of the differences in pressure by changing oal's
    iVohJkW.png

    ramshot powder company used to put graphs out like this 1 in their reloading manuals
    UlcjxB5.jpg

    Typically full house loads of fast burning powders aren't a good thing in the 9mm cases.
     
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