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Thread: Primer Cup Thickness

  1. #1
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    Feb 2003
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    Primer Cup Thickness

    My quest to track down some primer issues this season have lead me to some interesting discoveries.
    All info here was gathered directly by myself and my own measurements and by speaking directly to techs at manufacturing facilities.

    The common thought about the difference between making BR primers compaerd to standard primers is generally true. It seems like there are only one or two prople at a primer plant that make the BR primers. One senior tech told me that this person has sort of a "gift" for spreading the compound in the cups. And this person is generally the only one that spreads compound when BR primers are being run.

    Consistency from cup-to-cup is the key and it takes a highly trained and "gifted" eye to do it as closely as possible from tray-to-tray of primers.

    BR primers do undergo more scrutiny and more frequent quality control checks.

    The next info for cup thickness is from my own measurements. I am talking about the thickness of the cup at the bottom where the firing pin strikes. Not the wall thickness, or sides of the cup.

    CCI BR4 .027"
    Fed 205 .025"
    Rem 7 1/2 .022"
    CCI 400 .0195"

    I do not own a Fed 205M primer, so I could not measure cup thickness although I truly would like to since this primer is definately one of the top players in this game.

    A tech from CCI told me that the BR4 cup thickness is deliberately thicker since benchrest shooters tend to push the limits of pressure. My measurements indicate a 28% increase in thickness.

    Just a bit of interesting info that I thought I would share.
    Joe Cowan

  2. #2
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    Joe, that's a very interesting bit of work on the thickness of the cups. If you don't mind my asking, how did you measure them? I've thought about doing that but am afraid of disassembling live primers and wondered if fired primers would give consistent results. I also couldn't figure out a good way to actually take the measurement. Thanks.

    German Salazar

  3. #3
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    Feb 2003
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    I disassembled the unfired primers first.
    Took a small keyless drill chuck, placed the primer on the benchtop with the anvil down, slid the chuck over top of the primer and lightly tightened the chuck. Now I had a good solid hold on it.

    Using a heavy duty baiting needle I pointed the anvil away from my face and popped the anvil out.

    With a non-metallic pick I scratched the mixture out. Be VERY CAREFUL with this step. I had two of them go off. Keep pointed away from your face and wear safety glasses.

    I made an anvil exactly .500" long out of 1/4" round stock.

    Turned one end down to 3/32" dia about 3/16" long.

    This end goes up inside the primer cup.

    With the anvil being exactly .500" long, your micrometer readings will start @ .500" instead of .000"

    Place the primer cup on the anvil and measure away.

  4. #4
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    Joe, that's a well thought out procedure, but I'm not brave enough! Thanks for the info.

    German Salazar

  5. #5
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    Good information, and like German I ain't near brave enough!

  6. #6
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    Feb 2005
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    Hot Springs,ar
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    I wonder if there is a difference in the hardness.I always assumed CCI primers were harder than others.I was told that somewhere and don't know if it's true.Very interesting.I commend you on your work.

  7. #7
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    To keep them from going off

    all you have to do is soak them in water for a few minutes and leave them wet when working on them.

  8. #8
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    Sep 2007
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    Joe, were you able to take into consideration the concave and convex
    surfaces on each side of the primers. Also the BR stamp on the BR-4
    that is raised on the inside of each cup. I measured cups previously
    using a new ball bearing. I found little difference, but could not
    determine the brinell hardness with enough reliability

  9. #9
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    Jul 2005
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    Arlington, WI
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    Primer Cups

    I know for a fact that the BR4 cups are made from thicker material that the 400's and 450's.

  10. #10
    Join Date
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    washington.........STATE that is.
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    I LOVE this guy!!!


    Joe you ROCK
    -----------------------------------
    "I had two of them go off. " UNquote.....
    -----------------------------------


    Y'HEAR that guys? Did Joe STOP in his quest? Was he deterred???

    NOoooo, he persevered against blinding and deafening odds and he PREVAILED!

    GIVE Joe the blowtorch, he won't burn hisself....give JOE the bazooka, he won't start the jeep on fire



    Thank you JOE!



    My MAN!



    al






    BTW.....I chose to mess with primers once. I wanted to kill a bunch of them for use in firing pin fall and penetration experiments.

    I sprayed them with WD-40, didn't kill em.
    I soaked them over night, didn't kill 'em.
    I soaked them in water over night, didn't kill 'em.
    I soaked them in diesel over night, didn't kill 'em.
    I had best luck soaking them in lacquer thinner and even then a few spit a little....... but the beetlejuice did get 'er done

  11. #11
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    Sep 2007
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    There really is a simple way of both disasembling a primer and making it ready
    for testing whatever makes you happy.

    after seating a primer in an old case. hold the case mouth up
    just over a 5 gal bucket with water in it. Use leather gloves and
    long handled pliers and full face mask. Heat the head of the case
    with a propane torch. the primer will go bang and if you have kept it
    pointed at the water, you will find it un damaged at the bottom.
    You must of course keep the mouth of the case pointed in a safe
    direction, ie away from yourself. When your done be sure to
    crush the used case so it doesn't find its way back to your gun.
    There is a small splash, nothing that moms paper towels wont
    handle. You won't need to call your insurance man if you do this
    outside

  12. #12
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    Bob,

    I'm no metallurgist so bear with me here

    In my case I wanted to test the actual cup for hardness and also to use the cup exactly as it would be in a real firing situation. FOR ME I wanted the anvil left in and everything. I was also using my deadened primers to test for bullet set-back in the case under firing pin pressure.......... but on this note, would heating it like this change the reaction (hardness, toughness etc) of the cup?


    Does the copper cup "anneal" or otherwise change properties under the heat?


    thanks



    al

  13. #13
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    Feb 2003
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    Al
    I would say that heating would stand a much better chance of changing the hardness than not changing the hardness.

    Bob
    The concave portion was accounted for by working a slight radius on the top of the anvil mentioned above (forgot to mention that)

    Also, my dimensions were confirmed during a conversation with a CCI tech.

  14. #14
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    Joe, I spent some time last night researching this and found that there are specifications for cup thickness - alhough like all specifications, they're subject to sometimes loose QC and changes due to manufacturing exigencies. From George Frost's book Ammunition Making, which is a terrific resource on how factories make ammunition and components, I found the following information at page 60:

    " In order to keep control of cup height, the thickness of the metal strip from which the cup blank is punched must be held to close tolerances. Metal thickness specifications are as follows:

    Small pistol .0173 - .0178"
    Small rifle .0205 - .0210" - Commercial
    Small rifle .0240 - .0245" - Military
    Large pistol .0205 - .0210"
    Large rifle .0265 - .0270"
    Anvil, all .034 - .035"

    It is reasonable to have two sets of blanking dies and punches on hand. One makes a slightly larger diameter blank to be used when the metal strip is running on the thin side. The other set makes a smaller blank when metal is on the thick side of tolerances.

    These two dies produce cups of fairly standard height. The thicker brass strip would make a longer cup if the larget blank is used. The reverse would happen with the thinner brass and smaller cup.

    Blank diameter for a small rifle primer cup, using brass of .0240" thickness, would be about .2433". Brass of .0246" thickness would need a blank of only .2408" diameter to make a cup of the same height."

    There is a lot more, but I think that this section gives a feel for the manufacturer's perspective.

    German Salazar

  15. #15
    Join Date
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    Northern Dakota Territory, 1-days ride SW of Ft. Ransom in LaMoure Co.
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    Here are primer specs that I have:


    -----------------------------------------------------------------

    Thickness = A
    Diameter = B
    Height = C

    Small Rifle ---------- A ----- B ----- C

    CCI
    400 ----------------- .020" .1753" .109"
    450 ----------------- .025" .1750" .113"
    BR4 ----------------- .025" .1755" .109"

    Federal
    200 ------------------ .019" .1757" .111"
    205M ---------------- .0225" .1744" .1075"

    Remington
    6 1/2 ---------------- .020" .1753" .109"
    7 1/2 ---------------- .025" .1752" .110"

    Winchester
    SR ------------------- .021" .1750" .109"



    Large Rifle ---------- A ----- B ----- C

    CCI
    200 ------------------ .027" .2112" .118"
    250 ------------------ .027" .2113" .118"

    Federal
    210 ------------------ .027" .2120" .117"
    215 ------------------ -- -- --

    Remington
    9 1/2 ---------------- .027" .2100" .119"

    Winchester
    LR ------------------ .027" .2114" .121"
    Mag ----------------- .027" .2114" .121"

    -----------------------------------------------------------


    The NRA sells a book called "Ammunition Making" by George Frost. This book tells it like it is in the ammo making industry. It has information about primers, priming compounds, or even how to make primers, as well.


    Happy Shooting
    Donovan Moran
    Last edited by dmoran65; 05-09-2008 at 09:42 AM.

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