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Old February 21, 2012, 07:58 PM   #1
10 acre woods
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pressure signs factory and reloading

Ok so here is my frustration. In my research everyone worries about pressure signs like primer flow or primer bulge. Well while shooting factory rounds they show all the signs of over pressure but why is no one worried. Also when we see the smallest sign of the primer flattening out we get concerned, factory rounds are flat or bulging backwards. what is the deal with this.
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Old February 21, 2012, 08:32 PM   #2
davery25
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i haven't noticed any of this from factory ammunition but i do from my handloads for nothing other than ive been bumping the shoulder back too much.

you might want to have that gun of yours checked out by a smith
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Old February 21, 2012, 08:51 PM   #3
jepp2
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First of all recognize that primer flattening might or might not be a sign of overpressure. There are something like 25 different ways to determine if you are overpressure. Looking at the condition of the primers is just one.

My own personal experience is that I have seen flat primers with factory loads. This can be the result of at least 2 things. The first is factory tends to be loaded rather warm, so it is close to max pressure. But with their larger blended lots of powder it is safer for them to do so than you. The second and I feel this is more significant is that factory rounds tend to have the shoulder set back pretty far. This is so they will chamber in basically every chamber out there. The more headspace you have the more the primer backs out before the head of the case slams into the bolt face. This will make the corners of the primer flat even with moderate pressure.

My suggestion would be for you to learn the other 24 ways (signs of overpressure) and rely on a combination to determine if you are approaching maximum pressure.

Brass flow into the ejector opening and hard to lift bolt handles are more positive signs of overpressure than primers looking flattened.

Last edited by jepp2; February 21, 2012 at 08:58 PM. Reason: added link
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Old February 21, 2012, 09:03 PM   #4
Salmoneye
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Quote:
Also when we see the smallest sign of the primer flattening out we get concerned,
As already pointed out...

That doesn't make me get antsy till I look at all the 'signs'...
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Old February 21, 2012, 09:07 PM   #5
Zach W.
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Even super hot loads will not flatten primers if the haedspace is correct.

Starting loads will flatten primers if headspace is incorrect.

As stated, factory loads are sized small to ensure function in a wide variety of firearms.
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Old February 21, 2012, 10:14 PM   #6
davery25
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10 acre what rifle is it? Im willing to bet yours is a case of headspace rather than overpressure as previously stated.

are you getting what looks to be shiny extractor claw marks on the case head?
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Old February 21, 2012, 10:18 PM   #7
10 acre woods
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thanks jepp2 I was concentrating on one problem and not all I think I was playing it way too safe. That link helped a lot.
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Old February 23, 2012, 06:56 PM   #8
Slamfire
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On wet year at Camp Perry, I collected the long range brass from the AMU next to me and the USMC rifle team shooter on my point.

You could shake the primers out of some of this brass.

When you see case heads and primers that look like this, the pressures are too high.

AMU



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