White Powdery Residue Inside Fired Brass

[Dean2]

I was resizing some 378 Bee brass to 338-378. In one instance the entire shoulder separated from the body of the case, right where the shoulder starts. There was a significant amount of powdery whitish/grey residue inside the case, enough that I had to clean the inside of the die. Case and inside of neck were well lubricated, and it is the only one out of 25 that did it. I looked in the other cases and found it in two others but not the rest. I will bin the other two with residue.

These cases I bought as once fired 378 brass. Has anyone else seen this kind of residue that appears to have weakened the brass.

 

[Dean2]

Thought I would add some pictures. There was a lot more of the granular white stuff you can see on the neck in the second picture, but I wiped most of it away before I thought to grab a pictures of it.

 

[RegionRat]

The comments about white residues and the verdigris mean there is a risk of contamination, but keep in mind the location of the failure is also a risk that there was too much cold working. 50/50 risk of which is the primary probable cause.

A close exam of the rest of that batch for both the contamination risk and the cold-working/necking are in order.

If you have a bore scope, I would take a peek inside those and see if you find any that are a risk. A section of the worst ones would give you a clearer picture of the situation with respect to the over-work question. Plus, you would easily spot more contamination or corrosion risks.

 

[lobo56]

The comments about white residues and the verdigris mean there is a risk of contamination, but keep in mind the location of the failure is also a risk that there was too much cold working. 50/50 risk of which is the primary probable cause.

A close exam of the rest of that batch for both the contamination risk and the cold-working/necking are in order.

If you have a bore scope, I would take a peek inside those and see if you find any that are a risk. A section of the worst ones would give you a clearer picture of the situation with respect to the over-work question. Plus, you would easily spot more contamination or corrosion risks.

Can you help me understand about contamination of brass and how that could be done?
Is it from not cleaning brass correctly or is it a powder problem. Thanks and just trying to educate myself more.

 

[RegionRat]

Cartridge brass is primarily copper and zinc, with trace amounts of other. Brass is susceptible to a long list of chemicals some of which are less common than others, but the more common risks are dirty water, ammonia, and salts.

Improper cleaning can mean a lot of things since there are many ways to clean brass. Mistakes like using the wrong chemicals added into a tumbler, or leaving brass wet after wet tumbling are easy mistakes to make. Getting contamination from the ground at a range during wet weather is another easy mistake. This is often how salts, urea, or ammonia get into brass and are left sitting. Places where livestock have been concentrated like near corrals, paddocks, or pens, can have dirt that has concentrations of contamination that would be bad for brass if left sitting inside.

That blue-green color in your photos is an indication of a copper reaction called verdigris. Depending on how fast it was formed, would be an indication of how bad the contamination was. I would have to have it in the lab to tell you specifically what caused it.

 

[WildRose]

I was resizing some 378 Bee brass to 338-378. In one instance the entire shoulder separated from the body of the case, right where the shoulder starts. There was a significant amount of powdery whitish/grey residue inside the case, enough that I had to clean the inside of the die. Case and inside of neck were well lubricated, and it is the only one out of 25 that did it. I looked in the other cases and found it in two others but not the rest. I will bin the other two with residue.

These cases I bought as once fired 378 brass. Has anyone else seen this kind of residue that appears to have weakened the brass.

Most likely oxidation on really old brass that has significantly weakened it. I've seen the same thing before on dirty once fired brass that's been stored for a long time particularly in humid environments.

 

[WildRose]

Looking at those pictures I would also strongly suspect either it's not "once fired" and/or it has been fired in an oversized chamber.

You might want to run a micrometer over it and see if it's actually in tolerance.

Personally, I would dump the whole lot that shows any of that white residue. As the poster noted above there are a lot of things that can cause it and all of them are bad.

 

[Doom2]

Can you help me understand about contamination of brass and how that could be done?
Is it from not cleaning brass correctly or is it a powder problem. Thanks and just trying to educate myself more.

Most likely the contamination is from wet cleaning with improper cleaning agents or from reaction with hard water. Other sources include contamination from environmental factors from being left outside. Even storage inside can be an issue if the brass is subject to condensation. The usual most likely suspect in brass corrosion is ammonia. However, other contaminants can result in dezincification of the brass as well.

Based on the location I suspect that this is stress corrosion but without lab work that can't be confirmed.

As an aside, the British stored their ammunition in a horse barn in India a century ago during the monsoon season. It didn't end well. Season cracking occurs in copper-based alloys subjected to a residual or applied tensile stress and exposed to a specific environment, such as moist air containing traces of ammonia.

 

[Dean2]

I appreciate all the input, so some further info. Alberta has VERY low hunidity year round and the brass is stored in the house which is heated in winter and AC in summer so temp stays pretty much at 70F year round. I know the brass was once fired factory ammo, it came from a good friend and the brass is about 7 years old. The brass has never been cleaned and when I do clean brass I only ever use walnut shells and a vibratory cleaner, so it isn't contamination from using the wrong cleaners. The sized brass fits in my custom chambered 338-378 just fine so it is in spec. That leaves the possibility that the few that have the white powder picked up something from ground contact when they were being fired.

I already turffed any that showed white but I am going to take another real close look at the brass with a bore scope, good idea from RegionRat, and any that show any hint of white or corrosion will go in the brass recycle bin. Thanks for the help.

Resize from 460 to 338-378
Die sequence - Right to left, 378 seater, 378 FL, 338 seater part way, 338 seater the rest of the way, 338 FL for final. Neck thickness ends up at .0145 so no neck turning needed and the OAL is 2/10s under trim length.

378 to 338-378 is similar process just using the last two dies. All done with Imperial Wax as the lube.

 

[Petey308]

That's simply the color of brass tarnish. Copper has the blue-green looking tarnish, and will be seen where the bullet contacted the brass.

Your humidity levels would affect how much you get tarnish.

Just clean them and it'll be fine. It's not damaging to the structural integrity of the brass.

 

[QuietTexan]

^^ that's what I saw. Copper oxide, NBD. Not the root cause of the entire shoulder breaking off the case that cleanly and uniformly.

 

[WildRose]

I appreciate all the input, so some further info. Alberta has VERY low hunidity year round and the brass is stored in the house which is heated in winter and AC in summer so temp stays pretty much at 70F year round. I know the brass was once fired factory ammo, it came from a good friend and the brass is about 7 years old. The brass has never been cleaned and when I do clean brass I only ever use walnut shells and a vibratory cleaner, so it isn't contamination from using the wrong cleaners. The sized brass fits in my custom chambered 338-378 just fine so it is in spec. That leaves the possibility that the few that have the white powder picked up something from ground contact when they were being fired.

I already turffed any that showed white but I am going to take another real close look at the brass with a bore scope, good idea from RegionRat, and any that show any hint of white or corrosion will go in the brass recycle bin. Thanks for the help.

Resize from 460 to 338-378
Die sequence - Right to left, 378 seater, 378 FL, 338 seater part way, 338 seater the rest of the way, 338 FL for final. Neck thickness ends up at .0145 so no neck turning needed and the OAL is 2/10s under trim length.

378 to 338-378 is similar process just using the last two dies. All done with Imperial Wax as the lube.

I can't see now your sizing process could cause any problems. I do however seen a line on four of those at about the same point the case above cracked and that concerns me.

I have no idea what is causing that line but it is concerning to me.

 

[WildRose]

That's simply the color of brass tarnish. Copper has the blue-green looking tarnish, and will be seen where the bullet contacted the brass.

Your humidity levels would affect how much you get tarnish.

Just clean them and it'll be fine. It's not damaging to the structural integrity of the brass.

Green tarnish isn't the problem, the white residue is. That could indicate something that could seriously compromise the brass.

 

[Petey308]

Green tarnish isn't the problem, the white residue is. That could indicate something that could seriously compromise the brass.

I didn't say it was, only what it was from.

That white residue is brass tarnish/oxidation. Brass oxidizes as that color, copper is blue-green.

It's cause and effect of corrosion, simple as that.