Identifying Stress Fractures in Brass

[Bill1973]

I'm new to reloading, and I'm trying to figure out if I have a problem with some brass that I purchased used. After annealing 350 pieces of Federal brass, about 1/3 of it had a dark line appear below the shoulder. I'm wondering if these are stress fractures or signs where the brass has been stressed?

I was told it was once fired brass from Federal Gold Medal Match ammunition. I have an additional 300 pieces of brass from FGGM ammunition that I purchased new, fired from my gun, annealed, and reloaded, and none of those pieces if brass have these marks.

After taking several measurements using a Hornady headspace guage, I noticed that the used brass I purchased was consistently. 01 inches longer at the shoulder than the brass fired from my bergara b14 hmr. Is this additional length enough to stress the brass and cause fractures?

My main questions are 1. What are the black lines in the brass? 2. What caused them? 3. Are they safe to reloading?
I appreciate your help and advice.

Thanks,
Bill

 

[BoydAllen]

I would section one of the black line cases at right angle to the crack and see what that revealed.

 

[spclark]

Is this additional length enough to stress the brass and cause fractures?

My main questions are 1. What are the black lines in the brass? 2. What caused them? 3. Are they safe to reloading?

0.01" isn't much with Federal brass, generally believed to be somewhat softer than other brands. Are these cases growing in overall length also?

If you can use something like a paperclip bent into a feeler to get an idea whether there's a groove forming inside the affected cases at that point you'll have a better idea whether what you're seeing is signs of incipient case separation.

What cartridge is this stuff?

Typical for stress-induced case failure to happen closer to the case web. Case walls don't end at the web at a sharp angle, there's a radius formed inside where the sidewall transitions into the web metal. Where that radius begins is where case wall stretch tends to happen, not so much up near the shoulders.

I can't answer 1 & 2 without having them in front of my eyes. #3 I'd have to say "I think so" but caution not going overboard with the loads used.

When I've experienced case wall stress failure it's been quite obvious that a ring's forming that appears different in texture rather than color, a grainier appearance. And that feeler gage telltales a groove inside forming at the same point 99 times out of 100.

 

[riflewoman]

Are/were thos black lines visible before annealing?

 

[Rset]

Would you please provide information on your annealing process?

 

[Bill1973]

The lines weren't there before annealing. The overall length is pretty consistently. 01 inches longer than my other cartridges that I know were fired twice. They are coming in at 2.025 inches. I also just tried the paperclip and didn't feel anything different in those areas.

I have a friend who very is knowledgeable and has helped me a lot to get started. He is going to look at them and trim the brass for me.

 

[Bill1973]

Would you please provide information on your annealing process?

I made an annealer using an old microwave motor, an 8" cake pan, and a torch head. I used tempilaq at the neck and a stripe down the side of the case (borrowed from a friend. They were two different ratings; i think 750 ish for the neck and 400 ish down the side) when I first started to make sure I was getting the temperature correct. I've done it by sight since then. The casing drops and is in the flame for 6 seconds.

 

[Texas10]

Probably an artifact from your annealing process or perhaps a chamber mark. I'd certainly section a case or two to make sure, but a crack forming there on fairly new brass would be unusual to say the least.

 

[D-4297]

From the FWIW Dept. , It does appear that you are annealing a bit to far down the case , in my estimation . May not have any effect on your original question , but it can have a effect on future case stretch , and a weakening of the case walls . Compare your annealed case to factory cases annealed length and see where you stand . Have a local knowledgeable shooter give input on this . The dis-coloration of the case caught my attention , which prompted my post . Pictures never do full justice on these subjects .

 

[Rset]

I made an annealer using an old microwave motor, an 8" cake pan, and a torch head. I used tempilaq at the neck and a stripe down the side of the case (borrowed from a friend. They were two different ratings; i think 750 ish for the neck and 400 ish down the side) when I first started to make sure I was getting the temperature correct. I've done it by sight since then. The casing drops and is in the flame for 6 seconds.

Where do you position the flame on the case/neck/shoulder when doing the annealing?

 

[JimSC]

From the FWIW Dept. , It does appear that you are annealing a bit to far down the case

/agree
the discoloration is caused by oxides forming on the hot metal. The thickness of the oxide layer depends on the temperature, and the thin layer creates interference effects for different wavelengths of light, resulting in a rainbow effect

back to the original question , take a straightened paperclip or thin piece of wire use it to feel the inside of the case for a stress crack. If there is one there you can tell

 

[divingin]

Line looks way far up the case to be separation, which usually happens just above the web.

No idea what it is though.

As far as annealing, I usually put the tip of the inner blue flame just about at the neck/shoulder junction, with a bias, if any, towards the neck. That gets the neck heating quickly, and still anneals the shoulder of the case, without getting the body overly hot.

Can you run the brass through your annealer without the flame and see if you get a line? Brass usually doesn't get "stress cracks" all that easily, as it's pretty malleable.

 

[hfinkle]

who ever fired the brass first may have a carbon ring problem?