Start of case head separation? (It is a chamber scratch!)

[CA_Shooter]

Yes, that’s the concept.

Not to get ahead of myself, but let's say i find the consistent location. What do I do next and what does it tell me?

 

[MislMan]

Let’s say you shoot three more rounds. Each piece of brass gets another scratch/mark at the 10 o’clock position. You then take a very hard look at the surfaces inside your action that correspond to that location. Inside walls, ejector cut, or whatever. Maybe there is a slight defect in that area marking the brass.

 

[jim_k]

I’ve had a few come apart.... no joy..View attachment 1214710

The stylus is pointing at the ring which represents incipient case head separation. This is the pale ring which forms where the brass is getting thinner. It is not a sharp groove (not on the outside). The internal groove can be extremely difficult to feel. When you see this, toss the case. If the piece of brass is sized and/or cleaned, the pale ring may not be visible. The brass should be inspected before any processing.

 

[Tokay444]

My guess is you have a scratch in your chamber that’s transferring to the brass.

 

[CA_Shooter]

My guess is you have a scratch in your chamber that’s transferring to the brass.

Thanks for the idea. Why would the chamber scratch the brass only after firing vs loading and unloading a dummy round?

 

[CA_Shooter]

Let’s say you shoot three more rounds. Each piece of brass gets another scratch/mark at the 10 o’clock position. You then take a very hard look at the surfaces inside your action that correspond to that location. Inside walls, ejector cut, or whatever. Maybe there is a slight defect in that area marking the brass.

So its possible its either the action or the chamber. Why would it only scratch after firing and not loading and unloading a dummy round

 

[edwardware]

I see the same tiny cut on both twice and three times fired brass.

The scratch appears to be coming from outside the case. . . magazine, feeding, a loading tray, something.

Head separations start inside, because the pressure pushes the material out against the chamber. By the time they are visible outside, they are really advanced inside.

 

[Coyotefurharvester]

If the op hasn't been bumping the case shoulders(as stated) wouldn't there have to be a out of spec chamber to allow the brass to stretch to the point of separation. And the marks are on the outside of the case(to low also and not all the way around).

 

[jelenko]

Thanks for the idea. Why would the chamber scratch the brass only after firing vs loading and unloading a dummy round?

There's a bit more pressure when the case is fired than just chambering a case/round.

I've forgotten - do you have a borescope - even a Teslong?
With the work you've done so far, you've isolated the cause to something in the chamber. You could just use the borescope to inspect around the chamber at the distance the dent is on the case.
If you didn't find any thing doing that [which would be puzzling], you could index the case and fire the round. You could then just stare at the specific area indicated. Still, with the size of that dent, the burr/ridge you would think it would be pretty visible.

 

[CA_Shooter]

There's a bit more pressure when the case is fired than just chambering a case/round.

I've forgotten - do you have a borescope - even a Teslong?
With the work you've done so far, you've isolated the cause to something in the chamber. You could just use the borescope to inspect around the chamber at the distance the dent is on the case.
If you didn't find any thing doing that [which would be puzzling], you could index the case and fire the round. You could then just stare at the specific area indicated. Still, with the size of that dent, the burr/ridge you would think it would be pretty visible.

I don't have a borescope but I'll take a look to see if there are some burrs near the chamber that would be causing this

 

[ormandj]

Give your chamber a really good cleaning with a chamber brush and mop before you get too far down this path. Pick up a teslong rigid bore scope from Amazon. Then you’ll be able to figure this one out quickly, and have something useful for all kinds of things in the future!

 

[CA_Shooter]

SOLVED!

Thanks to everyone who assisted me with trying to figure out what was going on with these scratches. Turns out its definitely not case head separation.

I found the scratch at the beginning of the chamber (attached image)

This is a Krieger barrel. This was my first barrel install and my first high end barrel and I think I saw the scratch and ignored it (vaguely remember now but not 100% sure). Any ideas on what to do? Should I care about the scratches? Will it affect the brass in a negative way that I will see in my groups? What would have caused the scratch in the chamber? I have only used Dewey rods to clean this thing a few times now

So far I have about 200 rounds down the barrel

 

[jelenko]

First congrats!

But, isn't the mark on the case a 'dent' - i.e., it goes into the case?

If so, how would a scratch [vs a raised piece of metal] on the chamber wall cause a dent in the case? Maybe others might know.

 

[CA_Shooter]

First congrats!

But, isn't the mark on the case a 'dent' - i.e., it goes into the case?

If so, how would a scratch [vs a raised piece of metal] on the chamber wall cause a dent in the case? Maybe others might know.

Thanks! I was pretty confused for a while what was causing this and had some big concerns at first about case head separation, until people in this thread said it was not case head separation.

The scratches don't actually make a dent. Most are so faint that I cannot feel them with my fingernail.

I'm also not able to physically feel the scratch in the barrel's chamber with my finger

I made two dummy rounds a few days back that already had two scratches and after touching them a lot (to see if I was getting new scratches when chambering and unchambering) I have noticed the scratches seem to be a bit fainter (of course they are still there).

 

[ormandj]

Do you use a bore guide? What cleaning rod are you using?

Do you know if that was there when you got the barrel? I'm wondering if it was something from the chambering vs. something you did. The picture is hard to make out. I still suggest that Teslong rigid bore scope!

If it's in the chamber and from the chambering itself, your gunsmith should be able to help you out. Without being able to see the brass/feel the indentation, I don't think we can tell you if it's going to have any negative impact on the life of the brass, but it's worth asking your gunsmith about.

 

[CA_Shooter]

Do you use a bore guide? What cleaning rod are you using?

Do you know if that was there when you got the barrel? I'm wondering if it was something from the chambering vs. something you did. The picture is hard to make out. I still suggest that Teslong rigid bore scope!

If it's in the chamber and from the chambering itself, your gunsmith should be able to help you out. Without being able to see the brass/feel the indentation, I don't think we can tell you if it's going to have any negative impact on the life of the brass, but it's worth asking your gunsmith about.

Didn't use a bore guide but am using Dewey rods to clean the barrel. I've been extremely careful with the rod - I didn't nick it.

I put the barrel on myself - got a prefit from Krieger. You can twist it on yourself pretty easily...then use go/no gauges.

If all I need to worry about is the brass getting the scratch mark and not affecting groups I can live with it. Not really a big deal