Primer Pressure Sign?


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Old 09-01-2011, 06:50 PM   #1
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Default Primer Pressure Sign?

Hello,

I'm trying to decide whether this primer is flat enough to qualify as a pressure sign:







I'm thinking not quite.

Could be wrong.

It was a Nosler Ballistic Tip 0.323" 180 grain bullet on top of 41 grains of Varget and seated about a caliber deep.

This is a starting load. However, I fired it through my G88 "S" marked. It has a 0.323" chamber but retains the 0.318" bore.

Recoil was not hard at all, but was sharp. Reminded me a lot of a .30-30.

I had no gas blow back in my face, or any bad stuff like that.

Headspace checks out totally fine, and the rifle is in very good condition or I'd not have tried this to begin with.

The only possible pressure sign I can find is that primer -- and I'm not sure it really qualifies as flat.

I have plenty of 0.318" bullets, so if you folks think that this is indeed overpressure, it won't hurt my feelings at all. I just have to decide what to go with given the 0.323" chamber, and this is part of the process.

Thanks!

Josh



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Old 09-01-2011, 08:38 PM   #2
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It's hard to tell from a picture. I'd be inclined to say yes because I also see a bright ring around the case and indication of pressure and case head seperation.



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Old 09-01-2011, 09:53 PM   #3
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I am inclined to agree with you about it being not quite a pressure sign. A simple check might be to try reducing the load by 10% and check to see if the case looks the same. Or try a couple of the .318 bullets with the 41 gr. load and check the cases. Or if this load was accurate I would just keep shooting it.

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Old 09-01-2011, 10:31 PM   #4
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My starting load is 42gr Varget, 48 max.

Edit, I like IMR4320 better in 8x57. Best loads I've found for all my 8x57's. It could be the way the chamber was cut. Have you tried any surplus ammo?

Oh yes, load up some .318 bullets. You can also check out cast lead gas checks. I can give you recipes for them also. 170gr work very well. This guy makes the best.

http://www.beartoothbullets.com/bulletselect/index.htm

This guy is cheaper, uses the different mold and brittle hardness.
http://moyerscastbullets.com/pricelist.html

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Old 09-03-2011, 01:41 PM   #5
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I would say yes ,It even appears to have machining marks from bolt face.Better to use .318 bullets.

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Old 09-17-2011, 12:28 AM   #6
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Quote:
Originally Posted by rjd3282 View Post
It's hard to tell from a picture. I'd be inclined to say yes because I also see a bright ring around the case and indication of pressure and case head seperation.
Hello,

Where do you see the bright ring?

Thanks,

Josh
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Old 09-17-2011, 01:01 AM   #7
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The primer looks like it backed out a bit. I would say yes to pressure sign, but no to excessive pressure sign. No flow or cratering around the FP strike.

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Old 11-15-2011, 06:21 AM   #8
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Wouldn't the first sign of stress usually be either a bright ring, pale ring above the head, Or a split in the neck?

With my Enfield #4s and #5s, there have been some narrow, very light pale colored rings by the rim, but very few with splits in the neck.

My Spanish FR8 (match. bolt, excel. Win. Field Gauge results) reloads exhibit no stress at all, and this is after nine reloads.
I spent hours last summer reading about military 'cup' conversion to commercial psi. etc.

robocop10mm: What causes flow or cratering around the pin strike, and can you easily see it with reading glasses?

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Old 11-15-2011, 07:56 AM   #9
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High pressure will flatten the primer and cause the radiused edges to flow into the void around the primer. Excessive pressure will cause the metal of the primer cup to flow into the firing pin hole in the breech face. Sometimes these high areas will be mashed back down or sheared off when the bolt is unlocked. This can mask the appearance of the cratering.

And, yes it should be visible with minimal magnification (reading glasses). I used to be able to see it with my naked eye. Unfortunately, my naked eye needs help now.

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Old 11-15-2011, 10:34 AM   #10
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Looking at the pictures, I DO see signs of pressure to be concerned about. I see cylindrical lines on the face of the primer where it took on the machining lines of the bolt face. It is also obvious that the primer has flowed around the firing pin, and I agree with rjd3282, I do see evidence of case head separation. Hard to tel from the pictures, but I might see a small crack in the neck, and it appears to me that the primer has indeed pushed out a tad.

Back off by 10% on your loads and then post another picture of both cartridges side by side. My guess is they will look substantially different.



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