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Author Topic: Overpressure signs?  (Read 4596 times)

Offline CP

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Overpressure signs?
« on: May 15, 2017, 06:40:39 AM »
Do these primers show overpressure? 

The lower one has me a bit worried; seems bulged a bit.  But maybe I didn’t get it seated properly. 

Offline elkaholic123

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Re: Overpressure signs?
« Reply #1 on: May 15, 2017, 07:14:44 AM »
looks fine to me, they are not flattened out   :twocents:
elkaholic

Offline Biggerhammer

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Re: Overpressure signs?
« Reply #2 on: May 15, 2017, 07:20:41 AM »
They look good me. Especially the edges of the primers, nice and rounded.


Offline Hilltop123

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Re: Overpressure signs?
« Reply #3 on: May 15, 2017, 07:31:47 AM »
Here's some flattened primers, hope this helps.

Offline Bill W

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Re: Overpressure signs?
« Reply #4 on: May 15, 2017, 01:32:08 PM »
CP,  your rifle might just have a big firing pin hole.

Offline DaveMonti

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Re: Overpressure signs?
« Reply #5 on: May 15, 2017, 01:39:00 PM »
Overpressured primers will flatten out, like the pics that hilltop posted.  If they are rounded, all is good.  They can't "bulge" under high pressure as the case is forced back against the bolt face. 

Offline CP

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Re: Overpressure signs?
« Reply #6 on: May 15, 2017, 01:44:38 PM »
Thanks for the feedback, I'll keep working on this load.


Offline yorketransport

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Re: Overpressure signs?
« Reply #7 on: May 15, 2017, 01:49:29 PM »
Is it just me or does that bottom primer look like it's actually backed out a bit? Plus, by the time you've flattened the primer on a 30-30, you're already way beyond safe pressures. 

Offline CP

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Re: Overpressure signs?
« Reply #8 on: May 15, 2017, 01:59:40 PM »
Is it just me or does that bottom primer look like it's actually backed out a bit? Plus, by the time you've flattened the primer on a 30-30, you're already way beyond safe pressures.

It's either backed out a bit or it wasn't properly seated to begin with.

Offline Magnum_Willys

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Re: Overpressure signs?
« Reply #9 on: May 15, 2017, 02:36:39 PM »
Measure your brass above base and compare to lighter round. Can give you some feedback.
« Last Edit: May 15, 2017, 03:07:51 PM by Magnum_Willys »

Offline JDHasty

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Re: Overpressure signs?
« Reply #10 on: May 15, 2017, 02:58:39 PM »
Is it just me or does that bottom primer look like it's actually backed out a bit? Plus, by the time you've flattened the primer on a 30-30, you're already way beyond safe pressures.

Flattened primers can also indicate slightly excessive headspace and the primer has backed out then when the case stretches the head of the case will come back over the primer until it is stopped by the bolt face.  I have seen this happen quite a bit when people were making 7-30 Waters, 30 Herrett, 375 Herrett and in just plain vanilla 30-30.  I think it is more common with 30-30 than others because people assume that the cartridge will headspace on the rim and are not that careful to place the false shoulder so that the action will barely close on the case. 

Offline CP

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Re: Overpressure signs?
« Reply #11 on: May 15, 2017, 03:28:15 PM »
Measure your brass above base and compare to lighter round. Can give you some feedback.

I trimmed it to 2.030" before firing and it did not exceed 2.040" after firing and sizing but that's all I know since I tossed it in the pile with the others.


Offline yorketransport

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Re: Overpressure signs?
« Reply #12 on: May 15, 2017, 03:34:57 PM »
Is it just me or does that bottom primer look like it's actually backed out a bit? Plus, by the time you've flattened the primer on a 30-30, you're already way beyond safe pressures.

Flattened primers can also indicate slightly excessive headspace and the primer has backed out then when the case stretches the head of the case will come back over the primer until it is stopped by the bolt face.  I have seen this happen quite a bit when people were making 7-30 Waters, 30 Herrett, 375 Herrett and in just plain vanilla 30-30.  I think it is more common with 30-30 than others because people assume that the cartridge will headspace on the rim and are not that careful to place the false shoulder so that the action will barely close on the case.

I've seen that on lever and break actions and headspace is the first thing I thought when I saw that primer.

What make is the rifle?

Offline CP

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Re: Overpressure signs?
« Reply #13 on: May 15, 2017, 03:41:24 PM »
Marlin 336 - It's never done this before.  I'm thinking that I just didn't get that primer seated all the way

Offline hogslayer

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Re: Overpressure signs?
« Reply #14 on: May 15, 2017, 04:08:57 PM »
Not to try and derail the thread.  But what's does case web expansion really tell you about over pressure?  I have a very tight cut chamber and experience slight bolt lift and only have 2.5 thou expansion from factory brass.  I loaded a 300wm hs precision for a friend and he has zero signs of pressure but has 9 thou expansion?

 


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