overpressure signs


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Soybomb
August 27, 2008, 02:11 PM
So I think the signs of overpressure are a bit voodoo like anyway but does anyone believe they can be read in steps? Does flattening happen before cratering for example? Or can it just be either or?

http://cyber-byte.com/photos/reloading6.jpg
makes me ask, I think its time I learn more about it :D

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GLOCK45GUY
August 27, 2008, 02:14 PM
I'm prety sure flattening happens first, then the primer starts to try and "flow" around and into the firing pin/pin hole.

Others I'm sure will chime in, or do a search on the topic. It's been discussed b4.

Ol` Joe
August 27, 2008, 02:26 PM
Looks like a oversize fireing pin hole.

The signs don`t always come in steps. You can have sticky extraction with nice round primers. or primer pockets that won`t hold a baseball let alone a primer they`re so stretched, and no other signs.

Ridgerunner665
August 27, 2008, 02:33 PM
Looks like a oversize firing pin hole.

I agree...

And primers will lie to you about pressure, reading brass is much easier if its back up by a good chrono and a Sierra reloading manual.

R.W.Dale
August 27, 2008, 02:56 PM
Short of primers falling out I feel the primer and brass appearance is as much a function of your individual chamber than the load fired.

example 30-06 has a 60,000 psi pressure rating, 270win is rated at 65,000psi

now if you have a 8% overpressure 06 load, why would you expect to see pressure signs with this loading when the 270 which uses an identical piece of brass is within it's pressure spec at 65k psi. At what point do you expect pressure signs to show? If for example 270 win case doesn't show flattened primers or overly expanded cases till 70,000psi that might only be 8% overpressure for 270 but it's 16% overpressure for the same case in a 30-06

Load to the manuals and pay attention to what your chrony tells you and don't sweat what your primers look like

easyrider6042004@yahoo.ca
August 27, 2008, 04:42 PM
1. Did the fired case come from a 1911 type pistol?

2. Is the firing pin hole in the slide the correct size, meaning the pin does not wobble in the hole?

If the answer to both questions is yes:

3. The primer doesn't show any evidence of over-pressure. It looks normal except for the slightly elongated firing pin indentation.

4. If fired from 1911-action type of pistol or similar, the primer strike looks like the firing pin dragged a bit, upon firing, as the barrel swung down on its link, causing the elongated indentation.

5. Probable fixes would be, from free to expensive:
A. to clean the firing pin, spring and the firing pin hole in the slide, free.
B. to replace firing pin spring with a new factory spec piece. I'm assuming the current spring is not strong enough to retract the firing pin before the barrel swings down in recoil, this is cheap.
C. i don't recommend this because of the cost, but to reduce the inertia of the firing pin, you can replace it with a lightweight aftermarket pin like that in the Springfield Armory 1911 Lightweight. You may have to experiment with different springs to get this lightweight pin to work. Expensive.

mkl
August 27, 2008, 05:29 PM
So I think the signs of overpressure are a bit voodoo like anyway

I asked the Witch Doctor and the Witch Doctor said to me: "Ohh ahh, ooh, ahh ahh, tally walla, bing, bang, ohh ahh ahh: No pressure signs!"

Sorry, I couldn't resist.

If you are under 55 or so, you can't appreciate the reference, but the last three words of my quote are my opinion.:D

The Bushmaster
August 27, 2008, 05:54 PM
And that's "Ohh eee, ohh aah aah......" I'm over 65...:D

Flattened primers are caused when the firing pin/hammer drives the cartridge forward, the burning powder expanding the case against the chamber wall allowing the primer to back out a bit just before the case is slammed back against the bolt face/recoil plate thus smashing the primer in an attempt to reseat it. The lower the pressure the less smashed the primer, but still does not indicate an over pressure load...

NCsmitty
August 27, 2008, 06:17 PM
Short of primers falling out I feel the primer and brass appearance is as much a function of your individual chamber than the load fired.
I totally agree krochus. There are so many factors that can affect a load and just different brands of primers can have different cup thicknesses and will not show any signs. The illustrated case looks ok except for a funky firing pin hole and maybe a rough bolt face.
Bolt rifles usually have a stiffer bolt lift with higher pressure.

NCsmitty

mkl
August 27, 2008, 06:53 PM
I'm going to have to disagree with krochaus & smitty on this one...

If your primers fall out, your pressures are way past the tinsel strength of the brass web, which is probably in the 65,000 psi plus range.

The original post showed a 10mm pistol case. Now while I agree that the 10mm is a high pressure cartridge, I don't think it's designed for 60,000+ psi.

If you get case head/rim/web expansion of .001" in any cartridge, rifle or handgun, you are way over pressure. To get a primer to fall out, it would take at least .004" and the shooter would probably notice significant gas leakage.

Depending on the handgun, a 60,000+ psi load could have catastrophic results.

Personally, when I am working close to that kind of potential pressure, I use a micrometer to measure the head or web for expansion. If I get any, I back off six percent, and call that maximum for that gun/load combination.

YMMV...

ranger335v
August 27, 2008, 06:56 PM
"Does flattening happen before cratering for example? Or can it just be either or?"

Even for rifles, it can be both, either or neither. But common hand guns are limited to far less pressures than any rifle so attempting to gage safe pressures by primers can be disterous.

Any over pressure signs such as flattened or cratered primers, swollen or sticky case heads, loosened primer pockets, etc, in handguns only show up long after a blow-up is probable. Limit your handloads to the published loads in manuals, or less, and forget any attempts to hot-rod those cartridges!

That said, your 10mm Auto primers appear pretty normal to me.

Soybomb
August 27, 2008, 07:05 PM
I'm not sure the picture does it justice, I feel like there is a bit of a shadow that makes the ring around the primer look deeper than it really is and that in reality it is pretty flat. Paranoid?

Walkalong
August 27, 2008, 08:08 PM
If your primers fall out, your pressures are way past the tinsel strength of the brass web, which is probably in the 65,000 psi plus range.
Agreed. If your primers are falling out, you are on the ragged edge of trouble.

Your primer pic shows NO sign of pressure. That is quite normal. They can be much flatter than that, assuming a high pressure caliber, and be just fine.

Paranoid?
Nah, just being careful and asking questions. Smart, I say. :)

goon
August 27, 2008, 09:51 PM
That primer looks OK to me.

Soybomb
August 28, 2008, 12:31 AM
Ok so then the next question is, does anyone have any pictures showing what really really flattened primers look like? Something to help me tell what kind of difference we're talking about from just losing the rounded edges to true flatening?

Remo-99
August 28, 2008, 01:10 AM
yes i would agree also, by initial primer indication that the pressure level would appear to be 'normal' if the there is NO other indication of pressure problems of course and i'm assuming that the primer used is of correct specs for the caliber ie not a rifle primer (don't laugh it's happened before)
Someone had a pic of a flattened primer on 357mag load on another thread, I'm sure you see straight away which round had the problem.
http://www.thehighroad.org/showthread.php?t=388366
It's reply #12

scrat
August 28, 2008, 01:25 AM
And that's "Ohh eee, ohh aah aah......" I'm over 65...

Figures. Old coot. hahahaha god i remember that song.

Im 231 post behind you. Race to 5000.

Soybomb
August 28, 2008, 12:10 PM
Thanks for all the great info! So do magnum level rounds often leave a changed but non-flattened primer? My .38spl loads don't show the level of primer change as the 10mm do, higher pressure cartridge at work?

The Bushmaster
August 28, 2008, 12:23 PM
Yup...High pressure cartridge at work. .38 Special and .45 ACP are, by nature, low pressure cartridges. You can get flattened primers with both calibres if you play with the upper end of the +P range. Still not an over pressure sign.

JRadice45
August 28, 2008, 02:11 PM
What you could do as well is fire a few factory rounds and see what the primers are like. In the case of winchester primers use winchester cartridges etc. and compare.

R.W.Dale
August 28, 2008, 04:00 PM
What you could do as well is fire a few factory rounds and see what the primers are like. In the case of winchester primers use winchester cartridges etc. and compare.

NO you cant? Because first off a primer may not "flatten until you're WAAAAAAAYYYYY! over the limit" and secondly do you know what the specs are on the factory primers?

Read this article it gives a great explanation of why measuring case head expansion is just as unreliable as reading primers

http://www.shootingsoftware.com/ftp/dbramwell%20july%2019%2004.pdf

cliffy
August 29, 2008, 12:44 AM
Primer cases are designed to indent without metal above the surface. Cratering appears as Metal appearing above the crest of the flat surface of the primer. When a crater has a hole pierced through the metal in the center, HOLEY COW! BACK-OFF on excessive powder charges. Primer condition indicates overloads. Once metal smears off the back of a case, HOLEY COW Plus! I spend lots of time creating MAXIMUM loads for given conditions. Ambient Temperature increases are the major factor creating overloads. buy a bigger caliber before overloading any cartridge! My .243 Winchester loads are CAREFULLY designatinated MAXIMUM loads, dependant upon specific weather TEMPERATURES, HUMIDITY, and ALTITUDE. Backing-off on specific powder charges aliviates OH, NOs. Handloading is a challenging science, not a guess-fest. Extreme Accuracy should always surpass sheer velocity, although the two can often be the same! If a case sticks within its bore, BACK-OFF powder chargewise. cliffy

The Bushmaster
August 29, 2008, 11:24 AM
You better hurry up, scrat. Yer fallin' behind...:neener:

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