Pennsylvania Firearm Owners Association
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  1. #1
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    Default Primers and Interchangeability

    New to reloading and gathering my nuts to sustain the hobby for long after they make it impossible for me to buy ammo and I have questions regarding the interchangeability of primers. What can and cannot be swapped out? i e large pistol and large pistol magnum. Same with rifle primers. And what about pistol primers into rifle cases and visa versa? Explanations as to why or why not would be good too. If I can understand the reasoning I stand a better chance of remembering it without having to write it all down.
    Thank you for keeping me safe.

  2. #2
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    Default Re: Primers and Interchangeability

    Quote Originally Posted by Walleye Hunter View Post
    New to reloading and gathering my nuts to sustain the hobby for long after they make it impossible for me to buy ammo and I have questions regarding the interchangeability of primers. What can and cannot be swapped out? i e large pistol and large pistol magnum. Same with rifle primers. And what about pistol primers into rifle cases and visa versa? Explanations as to why or why not would be good too. If I can understand the reasoning I stand a better chance of remembering it without having to write it all down.
    Primers basically have 3 attributes: Energy, cup thickness, pressure tolerance. While cup thickness and pressure usually go hand in hand, there are differences where a primer could have a thinner cup for pistol-type firing pins but still better stand up to increased pressures of magnum loads.

    I'll attach an older table that calls out CCI primers specifically

    CCI_primers.jpg

    So while there's really only two types of primers, Small and Large, once you move outside the recommended usage you really have to test the
    specific load combination in a specific firearm to see if and how well it will function. Light strikes, Over pressure charges, blown or punctured primers,
    incomplete ignition of powers, Firearm explosions, Death, etc. are all possible with the wrong combinations.

    I personally have substituted STD for MAG and vice-versa within the same class (pistol or rifle with extensive low-powder-charge testing) and have only
    once substituted Small rifle for Small Pistol. But each situation is definitely unique, and even my 458socom rifle loads call for Mag Large Pistol primers,
    but that's mainly because of the different seating depths of the brass. The 357sig is a high-pressure pistol round and I routinely use MAG small pistol
    primers in it with slower powders for more complete ignition.
    Last edited by 85MikeTPI; November 27th, 2020 at 11:12 AM.

  3. #3
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    Default Re: Primers and Interchangeability

    I read that mag primers add a little pressure to the load over std . primers . I have used mag primers in place of std but I also don't load to the max .

  4. #4
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    Default Re: Primers and Interchangeability

    I would go here: http://castboolits.gunloads.com/forum.php to ask this question. There is lots of great info from long time, experienced reloaders. The site is not just about casting bullets and the such, but about reloading in every way shape and form.
    Ron USAF Ret E-8 FFL01/SOT3 NRA Benefactor Member

  5. #5
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    Default Re: Primers and Interchangeability

    OK so bare minimum it looks like I could use large pistol magnum in large rifle with no problems and small pistol in place of small rifle and probably visa versa with no issues. That's a good start.

    Thanks
    Thank you for keeping me safe.

  6. #6
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    Default Re: Primers and Interchangeability

    I'm pretty sure large pistol are different height from large rifle. Swap with caution to make of a solid primer strike.
    www.Steelvalleycasting.com is your new home for coated bullets and custom ammo.

  7. #7
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    Default Re: Primers and Interchangeability

    "Firing line forums " is a real good reloading site with some very knowledgeable members.

  8. #8
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    Default Re: Primers and Interchangeability

    Quote Originally Posted by Walleye Hunter View Post
    OK so bare minimum it looks like I could use large pistol magnum in large rifle with no problems and small pistol in place of small rifle and probably visa versa with no issues. That's a good start.

    Thanks
    Hmmm , IIRC , there was an extensive ''Everything you need to know about primers'' article in an old reloading manual , but forget which one , that detailed the differences. Pistol primers are meant to 'show' high pressure at substantially lower levels. Standard large pistol cartridges run 10-20k-psi , magnum pistols , 25-35k , large rifle - 35-50k-psi.



    From the CCI site. https://www.cci-ammunition.com/faq.html


    I have CCI Large Pistol primers, can I use them instead of the Large Rifle primers I need for my rifle loading?

    No. The primers are dimensionally different, as are the primer pockets.

    But I'm sure there are members who know much more about primers than CCI and will say it's OK.
    Last edited by abner13; November 27th, 2020 at 01:09 PM.
    I don't speak English , I talk American!

  9. #9
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    Default Re: Primers and Interchangeability

    Quote Originally Posted by Walleye Hunter View Post
    OK so bare minimum it looks like I could use large pistol magnum in large rifle with no problems and small pistol in place of small rifle and probably visa versa with no issues. That's a good start.

    Thanks
    No. small primer dimensions are the same. Large aren't.

  10. #10
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    Default Re: Primers and Interchangeability

    I'll mic 'em and see what I find.
    Thank you for keeping me safe.

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