What causes this?

[Canadian Bushman]

Hey guys what causing this, is there need for concern?

 

[RT2506]

If it is the soot on the case you are referring to it is usually caused by too little pressure. Meaning that you need to up your powder charge. Your load does not produce enough pressure to expand the case to fill the chamber properly thus allowing gasses to flow back between the case and chamber leaving the soot behind.

 

[jmitchell135]

I'm not sure I see anything wrong. Are you asking about the carbon on the neck? I think that's normal.

Eta: now that I blow the pic up I see. That seems to be a little excessive. I get a carbon ring on the necks of my cases, but nothing like that.

The poster above me said up the powder charge, but you could be looking at too little neck tension as well. There are a few reasons why the bullet would come out of the case before the brass completely expands.
Is this a bolt or semi auto?

 

[Bill Johnson]

Well, you got full body expansion, so that's good. Low pressure will be characterized by soot on the body, sometines partially colapsing the neck. It is a little unusual to see that much soot on the shoulder. While insufficient neck tension might cause this, I'd ask if you've ever annealed the neck and shoulder? That might fix it.

That said, because you got full body expansion and effectively sealed the chamber, I would not get too concerned. What was the load?

 

[Canadian Bushman]

Im getting sufficient pressure sending a 215 gn bullet at 2600 from a 308 case.

I do run very low neck tension on this load, about .0005-.001.

I just annealed these cases hoping that would help, this was the first thing that came to my mind. It only happened on 8 out of 50.

 

[royinidaho]

I just annealed these cases hoping that would help, this was the first thing that came to my mind. It only happened on 8 out of 50.

Only 8 of 50? Not much of something to be concerned with.....maybe.

I enlarged the pic and have some observations/questions.......

The pattern on the shoulder seems strange. Why would it so uniformly not reach the case body? Just worder'n.....

 

[Canadian Bushman]

Only 8 of 50? Not much of something to be concerned with.....maybe.

I enlarged the pic and have some observations/questions.......

The pattern on the shoulder seems strange. Why would it so uniformly not reach the case body? Just worder'n.....

Im not too worried but if i could figure ouf what's happening, maybe i could save some barrel life and if nothing else improve the consistency of my ammo. I usually get some soot on the necks but getting it this far up the shoulder is new for me.

The burn pattern is very concentric and even around the shoulder, and also among all eight cases.

What you are seeing there is in fact a reflection of light and not a bump.

 

[royinidaho]

I'm thinking you'll figure it out.

Let us know when you do.

 

[Canadian Bushman]

I'm thinking you'll figure it out.

Let us know when you do.

Thank you for the vote of confidence, if any ideas come about be sure to toss them in the ring.

 

[KYpatriot]

Were these rounds completely cleaned of sizing lube before firing ? Could it be that the case is not gripping the chamber walls until it has recoiled against the bolt and thus allowing some sooting before it expands to fill the chamber? If so you d also get getting some unwanted bolt thrust as well.

 

[Canadian Bushman]

Yes cases were completely cleaned of all lubricants and barrel has not been cleaned over aprx 75 rounds, so there is no reason for me to believe that there would be any sort of oil in the chamber.

Also lack of case friction usually shows high pressure signs on the head of the case which were not present on these 8 cases nor the other 42.

 

[Bill Johnson]

I'm with Roy. I think you'll figure it out. Please let us know when you do. It sure is a puzzlement, though. Just never seen neck fouling so even around the neck and have such a well-defined stopping point.

 

[ig25]

Hey guys what causing this, is there need for concern?[/QUOTE
If it happened while sizing. You had to much lub on the case or the chamber is letting the neck expand to much then when resizing it got crushed.

 

[Canadian Bushman]

I'm with Roy. I think you'll figure it out. Please let us know when you do. It sure is a puzzlement, though. Just never seen neck fouling so even around the neck and have such a well-defined stopping point.

Right now im leaning toward very light neck tension with brass in need of being annealed. Ive annealed the cases and am preparing to reload them. I will be able to tell if this is the problem shortly.