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Flattened Primers? Help?

 
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  #1  
Old 11-08-2011, 10:30 AM
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Flattened Primers? Help?

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
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Old 11-08-2011, 10:35 AM
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Re: Flattened Primers? Help?

need more info.
primer?
pic's?
bolt face pic?
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  #3  
Old 11-08-2011, 12:04 PM
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Re: Flattened Primers? Help?

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
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Old 11-08-2011, 05:02 PM
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Re: Flattened Primers? Help?

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.


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.
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Old 11-08-2011, 05:53 PM
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Re: Flattened Primers? Help?

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.
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Old 11-08-2011, 07:17 PM
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Re: Flattened Primers? Help?

Quote:
Originally Posted by boomtube View Post
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.
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 by Bart B; 11-08-2011 at 07:25 PM.
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Old 11-08-2011, 08:33 PM
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Join Date: Sep 2011
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Re: Flattened Primers? Help?

Quote:
Originally Posted by Dgutter View Post
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?

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.
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