Case head separation causing "nick" in chamber wall

[bsumoba]

I am shooting a 284 Shehane, 12x fired brass, 56.3 H4831SC, going 2880-2890 fps with 180gr hybrids in a 30" barrel. Pressure sign was seen around 57.5 gr based on my logbook.

Went to go shoot this morning and towards the end of my session, I had a case head separation. It was about 1/4" long and in two locations, just above the web area (I didnt save the case). It was not a complete case head separation. I fired 3 more rounds after and noticed that I was getting "markings" on the brass as shown below. Thinking something was wrong, I stopped and went home.

Borescoping showed a carbon ring and a section where I saw what looked like brass stuck to the chamber wall. I thought this was probably what was causing the markings. I yanked the barrel off to get a better look. After about 15 minutes of cleaning the carbon and the brass on the surface of the chamber wall, it was then apparent that the case head separation caused a nick in the chamber wall. Interesting.

I will fire this barrel again to see if cleaning helped alleviate the markings on the brass or if it will cause any other issues. This is "experienced" brass I am working with and will be retired most likely after a few more firings so I do not mind the brass starting to get some shallow markings on it, but this barrel only has 300 rounds on it and it is shooting great.

Have you had experience like this and did you keep shooting it?

 

[savagedasher]

284 used a rebated bolt face looks like the the case the extractor groove was cut too deep . That the first to me. Larry

 

[LHSmith]

It was a very hard lesson to learn because I am a "tight" PA dutchman (frugal), but brass is expendable and cheaper than destroying barrels, especially a shooter.
Savagedasher- brilliant deduction

 

[Eddie Harren]

284 used a rebated bolt face looks like the the case the extractor groove was cut too deep . That the first to me. Larry

Interpreter Up! Norm Crosby is here!

 

[swd]

It's hard to tell from the picture, is the case dented in or is it pushing out slightly? Either way a light polishing of the chamber is in order. If the case is pushing out in that area the chamber is gas cut it may need a set back. Try a light polish first.

 

[jpretle]

Gas cut in the chamber wall????
Might want to check those brass for the beginnings of case head seperation and some may even show gas cuts, leading to seperation.

 

[Cold Bore]

Went to go shoot this morning and towards the end of my session, I had a case head separation. It was about 1/4" long and in two locations, just above the web area (I didnt save the case). It was not a complete case head separation.

...it was then apparent that the case head separation caused a nick in the chamber wall.

Might want to check those brass for the beginnings of case head seperation and some may even show gas cuts, leading to seperation.

You mean.... just like the OP described in his post?

 

[jpretle]

Yes, what he said. There is a difference between a 'nick' and a 'gas cut', however. I can't see brass causing a 'nick' in the chamber.

 

[bsumoba]

Maybe I confused people. The picture of the case shown is NOT the one that had case head separation. It is the case fired in the chamber after the incident. The case itself has essentially a 'nick' in it, much like if you were to throw it on the ground and a rock causes a cosmetic defect on the case. Previous cases prior to the incident do not show this 'nick' mark, but the 3 rounds fired after the incident all show the same marking. The marking also looks very similar to the shape of the 'nick' in the chamber wall.

Yes, what he said. There is a difference between a 'nick' and a 'gas cut', however. I can't see brass causing a 'nick' in the chamber.

I cannot see brass or gases causing a 'nick' in the chamber wall either and spoke to this with someone else and he does not recall seeing this either. But, nevertheless, it did happen. The 'nick' was not there before as previous cases fired prior to the case head separation did not show the same signs as the ones fired after the case separation incident.

 

[bsumoba]

Gas cut in the chamber wall????
Might want to check those brass for the beginnings of case head seperation and some may even show gas cuts, leading to seperation.

I do check for them, pretty religiously. I have seen gas cuts before and I know what they look like. I just did not expect this to cause a 'nick' in the chamber. I know there is a lot of gas and brass, but for it to affect stainless steel is a new one.

 

[swd]

Polish the chamber if that doesn't fix it, set it back enough to get rid of the problem. I should have just said that the first time

 

[jsn]

There have been incidences of Winchester primer failures (on the radius) that lead to bolt face etching, I don't understand why some think it can't happen to the chamber wall when case head separation occurs.

 

[bsumoba]

There have been incidences of Winchester primer failures (on the radius) that lead to bolt face etching, I don't understand why some think it can't happen to the chamber wall when case head separation occurs.

That is true! LOL. Never thought of that.

 

[/VH]

Years ago, we used to trap shoot and quail hunt a lot. We used a lot of Federal paper hulls. After a few firings, the paper hulls would develop pin holes just above the brass. We would then use these hulls for 'shoot and shuck' hunting loads. Eventually I began having extraction problems with my shotgun and subsequently, it got to the point that cleaning the chamber didn't help much. So, I got to trying to figure it out and what I found was that those pinholed shells had eroded my chamber. A lesson was learned.

Also, I have seen a single primer leak etch the face of a S&W revolver firing pin bushing to the point where occasionally the cup of a subsequently fired primer would deform into the small 'nick' and lock up the cylinder.

 

[Nodak7mm]

I've experienced that very thing. Long story short, excessive headspace=head separation=gas cut into chamber wall. Each case fired thereafter formed into the gas cut creating a minute dimple on the case..

My cause of separation was a mis-marked go-gage and I'm not saying where it came from either. 0.016 headspace error will get your attention.. really sucked to fubar up a new chamber..

Cut er off and rechamber or live with the dingleberry in your cases..

 

[Alex Wheeler]

Bryan, you will not polish it out. If its not causing extraction issues and the barrel is shooting good, I would leave it be.

 

[Cool Tool]

I do check for them, pretty religiously. I have seen gas cuts before and I know what they look like. I just did not expect this to cause a 'nick' in the chamber. I know there is a lot of gas and brass, but for it to affect stainless steel is a new one.

I personally would like to see the piece of brass that separated what brand brass are you dealing with there is a wealth of knowledge on here a little info needed.

 

[K22]

I'm curious - wouldn't the previous firing of the case that separated shown that the case was stretching beyond normal limits if you were checking head space of fired cases before you reload them.

Also shouldn't there have been signs of incipient separation before the separation reached the point of damaging the barrel?

I'm asking these questions for learning purposes, not to find fault with your reloading methods. I'm just curious because I was taught to check the head spacing of fired cases and visual inspect them before I reload them. I'm wondering if you had done that would it have prevent the damage to your barrel.

 

[Terry_M]

I'm curious - wouldn't the previous firing of the case that separated shown that the case was stretching beyond normal limits if you were checking head space of fired cases before you reload them.

Also shouldn't there have been signs of incipient separation before the separation reached the point of damaging the barrel?

I'm asking these questions for learning purposes, not to find fault with your reloading methods. I'm just curious because I was taught to check the head spacing of fired cases and visual inspect them before I reload them. I'm wondering if you had done that would it have prevent the damage to your barrel.

OP says he had many firing on this brass "experienced brass" and brass flows toward the case mouth as it is fired. Over time all brass will fail, usually just above the web or in the case neck. It's just unfortunate in this instance that something was propelled sideways into his chamber hard enough to score it and leave a permanent mark. Not all case head separation is caused by improper head space. Yes by running a dental pick or some other small sensitive wire into the case you can feel when the case gets a rough or textured section just above the web. That does not mean instant failure, and if you're being frugile you can push those cases for additional firings. Question is how many more....

 

[snert]

Years ago, we used to trap shoot and quail hunt a lot. We used a lot of Federal paper hulls. After a few firings, the paper hulls would develop pin holes just above the brass. We would then use these hulls for 'shoot and shuck' hunting loads. Eventually I began having extraction problems with my shotgun and subsequently, it got to the point that cleaning the chamber didn't help much. So, I got to trying to figure it out and what I found was that those pinholed shells had eroded my chamber. A lesson was learned.

Also, I have seen a single primer leak etch the face of a S&W revolver firing pin bushing to the point where occasionally the cup of a subsequently fired primer would deform into the small 'nick' and lock up the cylinder.

Dang it! There goes all my feral pigeon loads!