Magnum primers for 9mm

Discussion in 'Ammunition & Reloading' started by amstutz, Jun 15, 2014.

  1. amstutz

    amstutz New Member

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    I stopped in my local gun shop on sat to inquire about supplies. No powder but he had a box of primers. When he handed it to me I noticed they were magnum primers (cci 550's). I looked puzzled and he quickly said "these are fine, no problem, don't worry use 'em just like the 500's I promise you will have no problems at all". I bought them. And now am having second thoughts. I'd like some opinions from you experts. Should I use them the same as the 500's? Or not?
     
  2. c3shooter

    c3shooter Administrator Staff Member

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    No, you don't.

    Magnum primers have a pinch of powdered aluminum, burn hotter, giving higher pressures.

    General rule of thumb is reduce starting load by 10%, but would check w/ manufacturer. Other folks may have advice for you.
     

  3. mseric

    mseric New Member

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    You will be fine, just start your load work at the "Start" charge and work up. No need to go below Start.
     
  4. Rick1967

    Rick1967 Well-Known Member

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    I use mag primers for everything. I just use the starting load in the book.
     
  5. BillM

    BillM Active Member Supporter

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    I see a 10-15 fps increase in velocity with small pistol magnum. If you are
    running a striker fired gun you may or may not have issues with light strikes.

    When I was loading for 9mm minor, 9mm major, 40 minor and 40 major for
    USPSA competition, I used Winchester SP magnum in everything--but ran
    a stock striker spring in my Glocks. No problems.
     
  6. samnev

    samnev New Member

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    That's exactly what I did with the magnum primers. Then work your way up very slowly. IIRC I ended up using about 10% less powder that what I had been using.
     
  7. JonM

    JonM Moderator

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    this.

    the issue with magnum primers in very small charge weights is over pressure. there is so much energy coming out of a magnum primer its possible to get detonation instead of a controlled burn.

    on the other hand since the charge weight in a 9mm is so small you probably wont notice it if it does.

    if your getting flattened primers in a 9mm your pressure is too high.

    cratering: where the primer metal is flowing into the firing pin channel

    [​IMG]

    flattened primer. not necessarily sign of over pressurein some cartridges. but in a 9mm it is the primer has flattened and totally filled the primer cup.

    [​IMG]

    none of these are ways to measure pressure. they are merely indicators you need to back off.