Flattened Primers? Help?

Discussion in 'Reloading' started by Dgutter, Nov 8, 2011.

  1. Dgutter

    Dgutter Well-Known Member

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    I've been reloading for my .25-06 for about a year now and have discovered what appears to be flattened primers. The thing is, I don't feel like I'm running hot loads. They are both a couple grains below max load so I'm not sure if its my untrained eye or if it has something to do with my particular rifle. And I also don't feel like I have hard bolt lift. Thoughts?

    The first load is 52.0gr. of IMR4831 pushing an 85gr. ballistic tip.

    The second load is 56.5 gr. of H1000 pushing a 115gr. Berger VLD loaded approximately .010 off the lands.

    And if anyone wouldn't mind posting pics of an example that may be a great help.

    Thanks,
    Dgutter
     
  2. MTBULLET

    MTBULLET Well-Known Member

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    need more info.
    primer?
    pic's?
    bolt face pic?
     

  3. Broz

    Broz Well-Known Member

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    Knock one out and see if it is "muffin topped" you will see this from looking at it from the side. If they are the same shape as they went in, you should be good to go. If they are indeed pushing out at the face you are getting into high pressure.

    Jeff
     
  4. larrywillis

    larrywillis Well-Known Member

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    Dgutter ......

    This picture shows what your primers look like as you work up a hot (but safe) load. Stick with loads that are published in a loading manual, and increase powder slowly - without exceeding maximum loads. Stop when your primers begin to get really flat.

    [​IMG]

    This picture came from : Primers (Pressure Signs)

    There's also a good article that explains what these fired primers are telling you. Keep in mind that some rifles develop chamber pressure much quicker than others.
     
  5. boomtube

    boomtube Well-Known Member

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    You're probably overly FL sizing your cases and setting the shoulder too far back. That's the major cause of flat, or 'muffin top", primer cups, not pressure. Try this:

    1. Size a case normally
    2. Prime normally
    3. Chamber the primed case and fire it
    4. Remove the case and see how proud of the case head the primer sits.

    If the primer is more than 2 thou high you need to reduce the amount of FL sizing you're doing. Understand we move the shoulder about .072" each full turn of a die; a 1/16th turn moves the shoulder about 4.5 thou (Some 2/3s of the normal full range of headspace tolerance!) so make SMALL die changes until you get it right. Get it right and your primers won't flatten and you'll greatly reduce the potential for stretching cases into a head seperation.
     
  6. Bart B

    Bart B Well-Known Member

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    I strongly disagree with this premise. Here's why.

    A normal, max, safe charge in a rimless bottleneck case whose head-to-shoulder datuim distance (otherwise called case headspace) is several thousandths short will do the following when fired:

    1. Upon primer impact by the firing pin, the case gets driven hard forward into the chamber shoulder and typically this sets the case shoulder backi a couple thousandths.

    2. As pressure builds up the case expands in all directions and the bullet gets started out of the case neck. The thinnist part of the case body, the front part behind the shoulder, expands hard against the chamber wall first. And at the same time, the case body stretches back from pressure. And it sucks the shoulder and neck back as it moves back.

    3. With pressure increasing, more of the case body presses against the chamber wall and contact works its way back on the case body. And the primer gets pushed out of its pocket a few thousandths.

    4. At some point the case stretches back until the head stops against the bolt face. This is as far as it goes. And this pushes the primer back into its pocket. This happens even with case headspace several thousandths shorter than chamber headspace; the case just stretches more. If case headspace is too short, head separation starts as cracks start in front of the extractor groove at the pressure ring.

    5. As the bullet goes down and leaves, pressure drops and ends up a zero. The case shrinks down a bit but its head to mouth length is now shorter.

    If too little powder is used, the primer will not get pushed back into its pocket.

    Proof of this can be seen by loading 10 rounds of rimless bottleneck ammo marked with the charge weight. Each has its case headspace at 3 thousandths shorter than chamber headspace. (Use new cases!!!) Starting with a max load then dropping 1 grain for each one, you'll end up with a series of rounds each with one grain less powder. Shoot the full charge firstl. Note how far its primer sticks out. Then fire each one in succession noting primer protrusion from the case head. Somewhere at 10 to 15 percent below max load, the primers will end up being pushed out of their pocket 'cause they ain't pressed back in with higher pressures. Use a case headspace gage to measure fired case headspace and, like I did when I did this test with new .308 Win. cases, cases ending up with their primers pushed out have a shorter case headspace than those whose primers were even with the case head.

    Wanna see "muffin top" primers? Start loading over max with new cases and you'll see those appear when pressure gets high. Note those cases are not too short headspace wise.
     
    Last edited: Nov 8, 2011
  7. NTRP

    NTRP Member

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    I think you're worrying about too much. Some primers have softer cups (Federal) and flatten prematurely. I didn't see what brand of primer you were using. Anyway, if you don't have ejector marks, sticky bolt, or increased recoil - just keep shooting, man.
     
  8. rscott5028

    rscott5028 Well-Known Member

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    Josh,

    You're probably right. But, I think it's at least noteworthy.

    If your primers really are flattening now, then you'll want to be aware of that as hot weather approaches.

    ...just a thought.

    -- richard
     
  9. Dgutter

    Dgutter Well-Known Member

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    You guys are a wealth of knowledge.

    For those asking I've been using Winchester Primers.

    The pictures make me feel a little better. My primers are somewhere between the second and third from left.

    And I was curious if I was FL sizing too much. I don't think I have created a very consistent method from batch to batch on how I set my sizing die. But I never would have thought of that being a cause of flattened primers.

    So to cure my problem...What is the most consistent way to set my sizing die from batch to batch? (I have lee dies, theres no set screw on the lock nut) Should I add a jam nut to the setup? And how do I properly set the depth for my specific chamber? How far back should I set the shoulder and how do I achieve that adjustment?

    Thank you guys for all your help.
     
  10. boomtube

    boomtube Well-Known Member

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    Bart: "I strongly disagree with this premise. Here's why."

    You are correct on most points but I disagree with your disagreement and here's why.

    Yes, the firing pin impact drives cases forward and, with bottle necks, it's usually about 1-2 thou, somewhat dependant on shoulder slope and brass hardness/thickness.

    The detonation of the primer adds to that driving forward force and the explosion instantly drives the primer cup hard against to the breech face, there's no need for powder pressure to do so. Add that 1-2 thou to whatever slack we may have overly resized onto our cases and the primer will be that much proud of the case head. And, yes, case head stretch-back will normally reseat the primer (but it won't "suck the shoulder back, chamber pressure will normally keep the case fore part pinned to the chamber). But not always.

    With the primer protruded as far as it can go and chamber pressure rapidly rising, it is not uncommon for the very thin primer skirt to be locked as hard to the pocket wall as the case is to the chamber. That can easily prevent the primer skirt from sliding back into the pocket as the head moves back, the effect won't be totally consistant for a lot of reasons so there will be variations in how much flattening we may see from round to round. But, it's certain that when a primer cannot slide in the ONLY way the exposed primer can move is sideways, pushing itself into the radiused mouth of the primer pocket. Result varies from a mildly flat to full "muffin top" primer, and all done at normal pressure, no excess pressure is required. Proper FL resizing to achieve minimum shoulder set back is the cure.

    IF a case has been neck sized, OR properly FL sized so it's a snug chamber fit, the primers can hardly move back and there will be very little flattening even at very high chamber pressures; the primers in a blown rifle may look quite normal!

    Thus, reloaders expecting flattened primers to be a reliable pressure indicator are making a mistake.
     
  11. larrywillis

    larrywillis Well-Known Member

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    What? ........

    If you don't have a complete laboratory of pressure testing equipment (and most shooters don't), how else are you going to work up safe loads? This isn't rocket science. Reloaders have been using the "flatness of primers" method for over 100 years.

    A dangerously hot load does look the same as a safe load.
    However, it's important to realise that when you work up a load, and the primers BEGIN to get flat . . . . that's when you stop increasing the load. Read the complete article on my website to understand "the rest of the story".
     
    Last edited: Nov 9, 2011
  12. Bart B

    Bart B Well-Known Member

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    All of my rimless and belted bottleneck cases are shorter after firing than before. Their case mouth is further back towards the case head after the case is fired. Sizing only the neck back to what my full length sizing dies do lengthens it a tiny bit, but not as much as full length sizing the body, too.

    I've shot several hundred "proof" loads in 7.62 NATO chamberd Garands (LC case & primer, 42 grains of IMR4475, 172-gr. bullet) that peaks at about 65,000 CUP, 83,000 PSI) and their primers were only slightly more flattened than the same load with a 147-gr. bullet (a standard M80 round producing 50,000 CUP, 58,000 PSI). No case head extrusion into the bolt face's ejector hole nor extractor cutout either. For all practical purposes both loads' case heads looked identical except for the slightly more flattening of the proof load's primer and it took a magnifying glass to easily see the difference.
     
    Last edited: Nov 9, 2011
  13. MTBULLET

    MTBULLET Well-Known Member

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    use a crono and see where your at.
     
  14. Bart B

    Bart B Well-Known Member

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    If one does this, the muzzle velocity they get won't mean much. It'll vary as much as 200 fps with different lots of powder and primers plus different bore and groove dimensions in different barrels plus the difference in how the rifles were held shooting the same load by different people. Muzzle velocity's a poor way to check pressure.