Case Head Separation Mystery - 7PRC reloads

TJCote

TJCote

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Interesting (and confusing) find in the brass pail at the range. I’m not sure I can explain what I’m seeing but maybe someone here can.

Approximately 20 rounds of reloaded 7PRC (some cases were marked with felt pen with the load recipe) were found in the brass pail. I couldn’t read all the writing on the cases but I read 175gr ELD-X and 180 gr M. The powder charges read 64.3, 64.0 (or possibly 69.0), 69.5 and 70.0gr. I couldn’t see powder type. One case was found with Fierce written on it. I presume that might be the rifle they were shot from.

All cases looked to be fired…based on the soot marks. All but 2 rounds had complete head separations and the 2 that weren’t separated were literally hanging on by a thread. All rounds, including the 2 unseperated, have severe “dents” in the case near the body/shoulder junction. The two remaining case heads had severe pressure signs (one missing a primer the other flattened real bad). Also both remaining heads had brass flow into the ejector hole. I didn’t find any of the separated heads. The only case heads I found were the two attached.

It certainly appears like the rounds were fired and were severely over pressured. Maybe a bad head spacing issue?/

All dents are smooth on the surface like they might be caused by hydraulic pressure from the outside. I’ve been reloading for many years but never experienced case head separation. Could those dents be caused by gas from the separated case head getting trapped between the case and the bolt/action. Then, once the pressure inside the case dissipated, the case collapsed.

What else could cause the denting?

Assuming all the brass failed during firing…
How would someone eject those failed rounds?
I wonder what the bolt and action of the rifle would look like after this kind of abuse!
I wonder what the experience level/IQ of the shooter/reloader might be?

Again, I can see one case head failure, maybe two…but 20…it seems inconceivable!
 

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good call on the dents, if the neck is sealed the pressure can be anywhere, shows up in the weak spots maybe.......
20 is for sure a mystery. Case bodies might fall out easily or push out with a rod
but to continue shooting after one or two failures????
boggles the mind
watch for a cheap Fierce to appear for sale somewhere, 'almost new, just one box fired' :sick:
 
TJCote said:
appears like the rounds were fired and were severely over pressured. Maybe a bad head spacing issue?/
Click to expand...
Headspace has nothing to do with pressure.

My bet is an inexperienced or stupid reloader maybe sized cases down too far and also used way too hot of a load.

What that guy doesn't know is that separated cases like that allow gas to cut into the chamber wall and will destroy the chamber.
 
I Dont Care About You said:
Headspace has nothing to do with pressure.

My bet is an inexperienced or stupid reloader maybe sized cases down too far and also used way too hot of a load.

What that guy doesn't know is that separated cases like that allow gas to cut into the chamber wall and will destroy the chamber.
Click to expand...
I had a couple of brass failures when I put the wrong bolt in the wrong rifle. Didn't happen all the time but often enough to get my attention. My loads are all the "starting" loads in the Lyman manual.
I have another rifle that I picked up on this site that has had a couple of brass failures. Time to take it to the Gunsmith.
 
I Dont Care About You said:
Headspace has nothing to do with pressure.
Click to expand...
Agree. However, excessive head spacing can sometimes mimic some high pressure signs. I’m specifically referring to flattened primers and case head separation. Resizing becomes excessive when headspace is larger than spec. Repeated and excessive case body stretching and normal resizing will lead to premature case head separation.
Normally the shooter/reloader would notice what is happening and stop before it gets to this point.
Odinson said:
I had a couple of brass failures when I put the wrong bolt in the wrong rifle.
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As someone who stores rifles and bolt separately, this is a good point.
 
Falconflyer said:
But why would the cases have dents in them, the high pressure should have ensured they were blown out if they were there prior to being fired.
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The dents are part of the mystery. Maybe it follows this sequence of events. I’m totally guessing, so please feel free to poke holes in this theory.
  • Rounds get chambered and fired.
  • Normal case neck expansion occurs and the neck of case is sealed against the chamber
  • The bullet is released. .
  • Case head separation occurs.
  • A small amount of HP combustion gas flows between the case and chamber. Some pressure gets trapped between the case and chamber/bolt head. Note: maybe this rifle action is not “vented”.
  • As the bullet makes its way down the barrel, the pressure inside the case drops below the trapped pressure outside the case.
  • Hydraulic dents occur as the case is partially crushed by higher outside pressure.

This might also explain how the separated cases can be extracted. Maybe the pressure differential which caused the dents made for easy extraction. Maybe the remnants of the failed case just fell out.

The final mystery is…if this occurred once, WHY would the shooter repeat it 19 more times?
 
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Sooty neck & collapsed shoulder = pressures too low to seal the case neck upon ignition. Upon ignition, gas pressure goes past the not expanded enough case necks & works its way back denting the case necks.

The case separations are a different matter entirely.

Don't try to combine the symptoms from 2 different problems.
 
I’m not sure that I agree that these are independent issues. Every case had case head separation and every case has similar hydraulic dents. A coincidence x20 seems unusual.

The case necks are fouled no more or less than normal.. These was no fouling past the neck/shoulder junction on the case which suggests normal ignition from a sealed case neck at the start…then things went south, probably, as full pressure was reached.
 
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TJCote said:
I’m not sure that I agree that these are independent issues. Every case had case head separation and every case has similar hydraulic dents. A coincidence x20 seems unusual.

The case necks are fouled no more or less than normal.. These was no fouling past the neck/shoulder junction on the case which suggests normal ignition from a sealed case neck at the start…then things went south, probably, as full pressure was reached.
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Definite headspace issues, maybe bubba the home gunsmith is still learning his trade.

The dents might be from underpowered reloads, or the dents might be happening after the cases separated and pressure entering from the backside of the case through the separation. Unless you have more info on the rifle, chamber, and reloads, there is no definitive answer.

The amazing thing is not the condition of the brass, but that somebody would fire 20 of them after the first obvious failure. That's incredible.
 
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TJCote said:
Agree. However, excessive head spacing can sometimes mimic some high pressure signs. I’m specifically referring to flattened primers and case head separation. Resizing becomes excessive when headspace is larger than spec. Repeated and excessive case body stretching and normal resizing will lead to premature case head separation.
Normally the shooter/reloader would notice what is happening and stop before it gets to this point.

As someone who stores rifles and bolt separately, this is a good point.
Click to expand...
That is exactly what happened. A Husky M-38 and a Carl Gustav 190something. The bolts fit and it would fire but when the brass failed, I felt some freckling on my face.
 
jamesharrison said:
Sooty neck & collapsed shoulder = pressures too low to seal the case neck upon ignition. Upon ignition, gas pressure goes past the not expanded enough case necks & works its way back denting the case necks.

The case separations are a different matter entirely.

Don't try to combine the symptoms from 2 different problems.
Click to expand...
Low pressure could make sense at only 60gr of powder. I load my 300PRC on the low end at 77-78grs. 60grs is way low.
 
If it was a case of gas pressure escaping after case separation, why are there no dents along the sides of the case instead of just along the case shoulder.

I've had case separations on more than 1 occasion in more than 1 rifle [usually, although not always, in #1 MK. III SMLE's with improperly prepped, for that rifle, more than once-fired brass, although a couple of times with 6.5x55 & 7.92x57IS]. There were never dented shoulders or sooted case necks.

I've also had cases with collapsed shoulders on different rifles, typically in either wild-cats or some old cartridge that I was not familiar with & for which no data was available, long before QL & GRT had appeared & before I bought a Powley computer. Because of that, I was very conservative in working up loads, because a long, long, long time ago when loading IMR4320 behind 196 grain bullets for an old sporterized M98 in 8x57, I not only blew the primer, but grossly expanded the primer pocket & obliterated the head-stamp. Had to use a club hammer to open the bolt. I still keep that case in my reloading tool-chest as a reminder.
 
TJCote said:
The final mystery is…if this occurred once, WHY would the shooter repeat it 19 more times?
Click to expand...
Because some people a FUKCING STUPID. 🤷‍♂️


Odinson said:
Now, I pay closer attention.
Click to expand...
I 3D printed bolt cases with custom labelling on them.


jamesharrison said:
If it was a case of gas pressure escaping after case separation, why are there no dents along the sides of the case instead of just along the case shoulder.
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Gas could flow forward between the case and chamber wall and when it hit the shoulder be redirected towards the case and cause the dent.
 
The only thing I can think of is: a reduced load, below the minimal powder required, accompanied with many full-length resizing.
 
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