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Thread: Primer Hardness?

  1. #16
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    I did this test several years ago

    The best way on any of the benchrest stuff is to do the hard work and test it yourself.
    Retired has it right, the target tells the story.

    Richard
    Attached Files Attached Files

  2. #17
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    Quote Originally Posted by antelopedundee View Post
    If the pressure inside of a case the instant before the bullet departs is 50,00 psi then it's equal in all directions, no?
    Yes, that's correct, but it's psi rather than pressure at ANY given point. John Kielly stated this a bit more eloquently earlier but I'm just being Wilbur and sayin' it differently

  3. #18
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    Quote Originally Posted by Kevin Gullette View Post
    ......Wilbur meant to type "83 pounds" ??
    Kevin
    I think you're right...but I'm pretty easy these days.

  4. #19
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    Quote Originally Posted by retired View Post
    in the br game. It DOES NOT MATTER.
    what matters is what happens on the TARGET.
    SO WORK UP A LOAD with each PRIMER and then go shoot the best.

    or do what most do , shoot a primer KNOWN to give uniform great results
    that tends to be federal small rifle or small rifle match.
    specific loads some time work better with a different primer.
    an example is the cc450 in 6mm dasher and rl15.
    I've never handled a small rifle primer so would the generalization about Federal being the best most uniform carry over to large rifle primers?

  5. #20
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    Quote Originally Posted by Wilbur View Post
    If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi.
    How does 83 pounds blow out a primer?
    Last edited by antelopedundee; 07-23-2019 at 03:34 PM.

  6. #21
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    if you have never handled a small rifle primer, you are pretty much wasting your time on most of these forums. IMHO


    Quote Originally Posted by antelopedundee View Post
    I've never handled a small rifle primer so would the generalization about Federal being the best most uniform carry over to large rifle primers?

  7. #22
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    Quote Originally Posted by antelopedundee View Post
    How does 83 psi blow out a primer?
    I believe Wilbur & Kevin, have it correct - that is, presuming that the firing-pin subtends 0.00166 square inches, or, 83/50,000.
    Are you talking "blown", or, "blanked" primers? Blown primers are caused by excessive pressure. Blanked primers are usually due to excessive firing-pin protrusion, and/or, sloppy firing-pin to firing-pin hole fit. Another cause [of blanking] may be thin, and/or brittle cups.
    I probably got pieRsquared rounded off incorrectly - but, at 50,000 Lb. per square inch pressure, it appears that, for a 1/16th (0.0625") diameter pin, the force against the pin-nose would amount to 153 pounds. I'm notorious for confusing radius and diameter. RG

  8. #23
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    Quote Originally Posted by R.G. Robinett View Post
    I believe Wilbur & Kevin, have it correct - that is, presuming that the firing-pin subtends 0.00166 square inches, or, 83/50,000.
    Are you talking "blown", or, "blanked" primers? Blown primers are caused by excessive pressure. Blanked primers are usually due to excessive firing-pin protrusion, and/or, sloppy firing-pin to firing-pin hole fit. Another cause [of blanking] may be thin, and/or brittle cups.
    I probably got pieRsquared rounded off incorrectly - but, at 50,000 Lb. per square inch pressure, it appears that, for a 1/16th (0.0625") diameter pin, the force against the pin-nose would amount to 153 pounds. I'm notorious for confusing radius and diameter. RG
    After asking my previous question, I stopped and thought about it for a second and came up with the same as you...152. something. I didn't follow up as I didn't get an answer to my question to begin with...so. No biggie.

  9. #24
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    Quote Originally Posted by R.G. Robinett View Post
    I believe Wilbur & Kevin, have it correct - that is, presuming that the firing-pin subtends 0.00166 square inches, or, 83/50,000.
    Are you talking "blown", or, "blanked" primers? Blown primers are caused by excessive pressure. Blanked primers are usually due to excessive firing-pin protrusion, and/or, sloppy firing-pin to firing-pin hole fit. Another cause [of blanking] may be thin, and/or brittle cups.
    I probably got pieRsquared rounded off incorrectly - but, at 50,000 Lb. per square inch pressure, it appears that, for a 1/16th (0.0625") diameter pin, the force against the pin-nose would amount to 153 pounds. I'm notorious for confusing radius and diameter. RG
    Cept nobody mentioned firing pin until your post, it was firing pin hole which was said to have a diameter of .062 inches and a calculated area of .00302 square inches. In the example cited of 50,000 psi the pressure available at the flash hole would be 50,000 psi and not 152. Going back to post 3 where a pressure limit of 41,000 psi was mentioned one would expect that 50,000 psi would blow that primer in some way. Otherwise with your 152 psi thing you're saying that when I check the air pressure in my truck tires that the pressure at the valve stem is NOT equal to the pressure elsewhere in the tire. The pressure inside of a round of ammo when the bullet is ready to start moving is the same everywhere inside the case be it primer, case wall or bullet base.

    If I took my truck wheel and put in a second valve stem of a different size then according to your explanation I should get a different reading at each one. I don't think that would be the case at all. How would a primer even flatten with only 152 psi pushing on it?
    Last edited by antelopedundee; 07-21-2019 at 10:42 PM.

  10. #25
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    If you had two tire guages and they gave you a different pressure on the same tire (quite common) ...what would cause that?

  11. #26
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    Quote Originally Posted by Wilbur View Post
    If you had two tire guages and they gave you a different pressure on the same tire (quite common) ...what would cause that?
    I didn't say gauges. The reading [with properly working gauges] should be the same at both valve stems is my point, otherwise your pressure measurement system is no good.

    By your logic a .30 cal flat base bullet with an area of .07447 sq in at 50,000 psi working pressure would have 3723 psi against it. I don't see that getting a bullet of a barrel at 2800+ fps.

  12. #27
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    Quote Originally Posted by antelopedundee View Post
    I didn't say gauges. The reading [with properly working gauges] should be the same at both valve stems is my point, otherwise your pressure measurement system is no good.

    By your logic a .30 cal flat base bullet with an area of .07447 sq in at 50,000 psi working pressure would have 3723 psi against it. I don't see that getting a bullet of a barrel at 2800+ fps.
    The two key issues are square inches (area) and calibration (the tire gauge): 50,000 PSI is just that - 50K pounds of force applied to each square inch: your muzzle pressure is pretty spot on. You are overlooking the rate of expansion = speed! RG

  13. #28
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    What exactly is PSI...

    I may have it wrong....thought it meant "pounds per square inch" rather than just "pounds". My earlier point concerning the tire gauge was that they are calibrated to report a pressure in PSI rather than what is experienced at the valve stem. Further, the tire pressure gauge sees the pressure at the gauge rather than the stem pressure...which may or may not be different....just like the primer sees a bit more pressure than the flash hole.

    That said, it doesn't matter which of us is right or which of us is wrong....won't change things in the slightest. If your primer doesn't look good you need to try another primer or reduce the powder charge.

  14. #29
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    Quote Originally Posted by Wilbur View Post
    I may have it wrong....thought it meant "pounds per square inch" rather than just "pounds". My earlier point concerning the tire gauge was that they are calibrated to report a pressure in PSI rather than what is experienced at the valve stem. Further, the tire pressure gauge sees the pressure at the gauge rather than the stem pressure...which may or may not be different....just like the primer sees a bit more pressure than the flash hole.

    That said, it doesn't matter which of us is right or which of us is wrong....won't change things in the slightest. If your primer doesn't look good you need to try another primer or reduce the powder charge.
    I gathered/interpreted from your comment that you would say that 2 valve stems of differing diameter would give 2 different pressure readings for the pressure inside the tire.

    As for this comment..............

    "If the pressure is 50,000 psi then the pressure within a .062 primer hole would be 83 psi."

    While the corrected value was 152 since it is acting on a small area then the pressure available at the flash hole and then to the primer on the other side is in effect 50,000 psi when normalized to 1 sq in. A better answer IMO to the question preceding it would have been the equivalent of 50,000 psi as it is everywhere inside the case.

    So in your opinion is primer hardness a useful indicator of whether or not a primer will give more consistent shot to shot velocity variation? It seems that ones that are GRAB Generally Recognized As Best are the ones that RG told me long ago are the softest.

  15. #30
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    No, that's not what I'm saying at all...when the air exits the valve stem it enters the tire gauge which is a consistent area and calibrated to read psi....it's not seeing the actual psi but is calibrated to show us something really close.

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