Ring Around the Case

[Rocketmandb]

For some reason, every case from my last range trip has a ring around it. I can't feel it at all, case is smooth. Same location on every case, though a couple are less pronounced (case on right side below). This is the 6th firing of these cases through the same chamber. Never appeared before.

Any ideas what is causing this?

 

[culater]

Are annealing your brass. If so it might be over done

 

[Rocketmandb]

Are annealing your brass. If so it might be over done

I am, but no differently than I have over the previous 5 firings.

 

[culater]

Take a empty fired case then and put it in the chamber and cycle it a few times. An see what happens you might have a burr in your chamber. If nothing happens then reevaluate your annealing process

 

[spife7980]

Any unfired to make sure it wasn’t there before pulling the trigger?
Usually when I find something like that’s it’s actually from the trimmer guide bushing or the box edge etc.
I assume if you had a bore scope you would have said as much which would make it an easy peek in the chamber to see if something coincides.

 

[Rocketmandb]

Any unfired to make sure it wasn’t there before pulling the trigger?
Usually when I find something like that’s it’s actually from the trimmer guide bushing or the box edge etc.
I assume if you had a bore scope you would have said as much which would make it an easy peek in the chamber to see if something coincides.

Sorry, should have mentioned that. I scoped the chamber and it's clean.

 

[Rocketmandb]

The other thing to mention here is that my chamber is undersized (diameter). Could this be a result of my sizing die not sizing it down enough, meaning it's essentially acting like a neck sizer?

 

[TheBoctor]

So how long did you leave these to ride around in the box in your truck?

I bet that the ring is the same height as the holes/dividers in your ammo box....

 

[Rocketmandb]

So how long did you leave these to ride around in the box in your truck?

I bet that the ring is the same height as the holes/dividers in your ammo box....

It's the ADG ammo box and they were upside down in it, so it doesn't marry up.

 

[Rocketmandb]

Any unfired to make sure it wasn’t there before pulling the trigger?

It was definitively not there before chambering. Can't say whether it wasn't there after chambering and before pulling the trigger.

 

[6.5SH]

WFT trimmer can make marks like that but are usually visible before firing.

 

[Rocketmandb]

WFT trimmer can make marks like that but are usually visible before firing.

Yeah, I always visually inspect post seating - and I wrote on every case as this was a load dev validation trip. I would have seen the marks then.

 

[6.5SH]

Try bore scoping inside the cases to see if there is a corresponding internal mark?

 

[Gee Kay]

check your reciever for debris or feed lips on your mag for a tiny burr.

 

[1moaoff]

Kinda looks like marks from spinning in magazine.

 

[Rocketmandb]

Kinda looks like marks from spinning in magazine.

Yeah, but since I was validating load dev, I was single loading all of these. My current thought is that my sizing die, though smaller than most, is still not sizing my brass enough/at all, and after 6 firings it expanded just to the point where a minute aberration in the chamber is rubbing the case on extraction. If it's all the way around the chamber, I'd think it could make a ring mark even from the partial rotation during extraction - I think.

What I'm going to do is order a new custom die. I was only using 50 of my new ADG cases to see if what I am presuming happened would happen. I think I will now use a fresh 50 and wait for the new die to arrive to play with these cases again. I'll see if I get any similar marks on the new brass.

 

[918v]

For some reason, every case from my last range trip has a ring around it. I can't feel it at all, case is smooth. Same location on every case, though a couple are less pronounced (case on right side below). This is the 6th firing of these cases through the same chamber. Never appeared before.

Any ideas what is causing this?

View attachment 7513781

case head separation

 

[PinesAndProjectiles]

case head separation

Agreed. Have you measured fired brass at the datum on the shoulder and then after sizing?

How far are you bumping shoulders?

 

[Rocketmandb]

Agreed. Have you measured fired brass at the datum on the shoulder and then after sizing?

How far are you bumping shoulders?

Bumping .002" I'll cut one open tomorrow and look along the length of the brass.

 

[Rocketmandb]

Agreed. Have you measured fired brass at the datum on the shoulder and then after sizing?

How far are you bumping shoulders?

Just double checked the measurement and resized a case (die hadn't moved) and it came right in at .002".

 

[Rocketmandb]

Try bore scoping inside the cases to see if there is a corresponding internal mark?

No marks

 

[6.5SH]

No marks

Sometimes imminent case separation is visible that way. Curious to hear what your planned case dissection shows.

 

[Joel Danielson]

Just double checked the measurement and resized a case (die hadn't moved) and it came right in at .002".

Take a paper clip and open it up enough to run the edge inside the case where the line is. You will be able to feel if there is an internal problem without having to cut one open. That area is not typical of where you find case separation. I think you are on the right track with a tight chamber that is marking the brass that needs to be full length sized rather than just shoulder bumped.

 

[Rocketmandb]

Take a paper clip and open it up enough to run the edge inside the case where the line is. You will be able to feel if there is an internal problem without having to cut one open. That area is not typical of where you find case separation.

Did the paper clip thing too. No issues.

I think you are on the right track with a tight chamber that is marking the brass that needs to be full length sized rather than just shoulder bumped.

Yeah, I just don't think my existing FL sizing die is small enough, even though I had it made small to begin with.

 

[918v]

Sometimes cases separate higher on the body. I sometimes see cases stretch like an accordion. You can see the ripples if you hold the case just right against the light.

 

[Joel Danielson]

I would make a couple measurements from base to where the shoulder starts on brass that wasn't fired in the last outing and see how that compares to a similar measurement on the brass that was just fired. If it is stretching that far up on the case, there will be a difference in that measurement. In my 40 plus years of reloading, most case separation happens just above the web.

Are you noticing any pressure signs with these loads, ie...sticky bolt lift, flattened primers, extractor marks on the brass?
I know the question was asked earlier, but what method/equipment do you use for annealing? The area where the lines on the cases are is about where you could be at for brass that is too soft from over-annealing. That would not show up until after the case was fired the next time.

 

[Rocketmandb]

I would make a couple measurements from base to where the shoulder starts on brass that wasn't fired in the last outing and see how that compares to a similar measurement on the brass that was just fired. If it is stretching that far up on the case, there will be a difference in that measurement. In my 40 plus years of reloading, most case separation happens just above the web.

Are you noticing any pressure signs with these loads, ie...sticky bolt lift, flattened primers, extractor marks on the brass?
I know the question was asked earlier, but what method/equipment do you use for annealing? The area where the lines on the cases are is about where you could be at for brass that is too soft from over-annealing. That would not show up until after the case was fired the next time.

Pressure signs: none
Annealing: Annie Annealer - same setting as always. Also, I anneal to just below the shoulder and this is well below where I stop. And these lines are very distinct - they really do look like something rubbed along the outside of the case.
Comparing to Unfired: I fired all cases I've shot for this chamber - it's new. I did resize one to compare and validate, and it's .002" less pre/post.

 

[Joel Danielson]

I agree with your assessment. Only other thing I can think of would be to check head space. Is this a barrel nut setup that you set the head space on? Have you checked to make sure the barrel is still torqued to the proper settings?

 

[equilibrium]

Any excessive brass growth?

Paperclip test done?

 

[Expert684]

Looks like case separation as mentioned. I have a paperclip that is straight, then I file the end to a point, bend it 45-90 degrees and I drag it up and down in the case. I’ve seen it in semi autos lower in the case.

 

[Steel head]

Looks like marks from a magazine and they spun a bit when loading

 

[Expert684]

Polish or use machine dye marker on an empty case, insert case in the chamber, close the bolt then open and extract. There should be a mark on the case if the chamber has a burr. Plus the ring if one prints would have the same rotation as the bolt.

 

[Gee Kay]

marks are way too high for case head separation signs

debris in your die perhaps?

 

[Smittiac]

Ammo box it looks like to me, the MTM ones(green 100 count) only ones I have and all my brass has a line around that point from the plastic spacer.

 

[Rocketmandb]

Any excessive brass growth?

Paperclip test done?

No to excessive growth, yes to test - no issues found.

 

[Rocketmandb]

Looks like marks from a magazine and they spun a bit when loading

I was single feeding - didn't use a mag.

 

[Rocketmandb]

marks are way too high for case head separation signs

debris in your die perhaps?

The marks weren't there either post-sizing or post-seating. Only after firing.

 

[Joel Danielson]

Could you answer those questions one more time for us please...

 

[Gee Kay]

The marks weren't there either post-sizing or post-seating. Only after firing.

then it leaves receiver

 

[Gee Kay]

what if you chamber an empty case then eject it and see if it leaves marks, process of elimination.

 

[Rocketmandb]

what if you chamber an empty case then eject it and see if it leaves marks, process of elimination.

I'm going to take one of the more egregious cases and mark it up with a sharpie and see what happens.

 

[1moaoff]

Can you chamber fired brass before sizing it? If so it may not be fully stretched or stretching in the chamber. When setting up body bump in tha past I have taken a case and fired it a few times until it was snug to chamber to see what was actually going on. I found i was sizing before I needed to on that gun. I could have neck sized only at first until brass fully stretched and remained chamber size.

 

[Rocketmandb]

Ok - I'm leaning very much toward this being a small chamber issue and my die isn't quite small enough to properly size.

- First, when I chamber a 6x fired case, I get resistance.
- When I chamber a 6x fired case that I've sized, I get less resistance, but I still get some.
- When I chamber a new case, no resistance, as has been the situation for the first 5x fired cases.
- Below are three shots. One of a before/after of an unsized 6x fired case marked with a Sharpie, a closeup, and another of that same case cut open
- The before/after shows a few marks, but nothing conclusive - EXCEPT - when you look at the close up, you can see more horizontal marks. They are difficult to see with the naked eye, and I didn't see them until I was comparing the before/after pic up close.
- The cut case looks healthy. RIP, your sacrifice will not be forgotten.

 

[PinesAndProjectiles]

The marks are visible in three of the pictures.

Do the marks show on the 5x fired cases? Can you post pics?

When adjusting your die, does it make contact with the she'll holder during the sizing process?

 

[Rocketmandb]

Do the marks show on the 5x fired cases? Can you post pics?

Unfortunately, I have no 5x fired cases. When I realized the chamber was a bit undersized, I decided to run these cases only to see what would happen. I expected that after 4-5 firings I'd possibly get a heavy bolt release or other symptom that you'd expect with just neck sizing. What's happening here seems to be a condition that's appearing just short of that. Because a sized case chambers a little easier than an unsized case, it appears that my sizing die is small enough to do a little, just not enough for full sizing in this particular chamber.

When adjusting your die, does it make contact with the she'll holder during the sizing process?

No. It maintains a tiny (as in thousandths) amount of separation at the top of the stroke.

 

[PinesAndProjectiles]

Can you scrounge up a new piece of brass and do some testing with it?

 

[2aBaC̶a̶]

Can you feel the marks with a fingernail or is it visual? I would sharpie the whole case. It will rub off in either your die or your chamber wherever its rubbing. Then borescope the one that makes the marks to see where it rubbed off. Slight variations are not always visible in a clean chamber or die.

If you cant feel it, I wouldnt worry about it. Likely just close tolerances.

I started having actual case head separations and it showed up as a single line or crease closer to the head. Some even venting gas.

 

[Rocketmandb]

Can you scrounge up a new piece of brass and do some testing with it?

I've cycled new brass and it chambers with no issues and there are no marks. I measured just forward of the case head on each a new case, one of these 6x fired cases, and one of the cases from my last chamber. When I took the same measurement from once-fired cases out of my current chamber, they were .529.

This is why I'm leaning toward it being an undersized chamber/die issue. My die is just not sizing it down enough.

 

[918v]

What does that have to do with a circular mark around the case suddenly appearing after firing? There was no mark before firing. Suddenly there is a mark after firing. Clearly, the mark was caused by firing. What happens to the case during firing? It expands and grabs the chamber. It stretches. It stops against the bolt face. It releases its hold on the chamber. It extracts.

 

[Rocketmandb]

What does that have to do with a circular mark around the case suddenly appearing after firing? There was no mark before firing. Suddenly there is a mark after firing. Clearly, the mark was caused by firing. What happens to the case during firing? It expands and grabs the chamber. It stretches. It stops against the bolt face. It releases its hold on the chamber. It extracts.

After discovering those other marks on the closeup, I think I should amend my statement to "There were no marks that I could easily see."

On extraction, the case rotates a bit. If it grabs too much after firing, then where it's grabbing would rub against the case. Perhaps the rubbing was occurring on previous firings, but wasn't enough to easily catch (like the other marks).

I'm open to other explanations/theories, but the cut case isn't showing any signs of irregular case stretching, and nothing matching the external marks. The chamber is definitely small (at least .0025 under Saami).