Can someone explain this chamber ring of residues?

[E-T-M]

I got this dirty ring in the chamber of my bolt action rifle after a shooting session. the width is about 25% of the chamber length and it is located right in the middle of the chamber. The black edge is towards the shoulder and the uneven edge is towards the base. The residues wipe with a dry patch relatively easily. Altough the color looks brown on the pic, the residues are black on the patch.

Any idea where this comes from? The chamber was clean before firing. If this was carbon fooling from firing, it would probably also show further up towards the shoulder in the chamber. I do not see corresponding marks on the fired cases. Could this come from a dirty brass, perhaps brass that were not cleaned enough from the lube when reloading?

I typically do not look through the borescope before cleaning the barrel. So I have no idea whether this is a common occurrence or something unusual. Curious if you have seen something like this and can explain the origin.

Thank you!

ETM

 

[acloco]

Residual case lube??

 

[243Lapua]

Old solvent

 

[joshb]

Residual case lube??

My guess too.

 

[JMayo]

Action cleaning tool with 40 cal swabs after cleaning everytime.
Surprised you're not having hard bolt closure.

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[E-T-M]

Action cleaning tool with 40 cal swabs after cleaning everytime.
Surprised you're not having hard bolt closure.

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Brownells has 234 SINCLAIR INTERNATIONAL products for Sale Up To 91% Off including Reloading, Tools & Cleaning, and Gear.

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Thanks JMayo - I did not experience hard bolt closure, but I did experience hard bolt lifts about two third through the session, which is why I had a peek through the borescope after the session. I am pretty good with my cleaning regimen and I do clean the chamber and lugs. My guess is that was caused a poorly cleaning job on the cartridge cases I shoot that day - they probably had some lube left over that accumulated in the chamber throughout the session, as others have mentioned.

 

[E-T-M]

My guess too.

Thanks Joshb - this is probably what happened,

 

[E-T-M]

Residual case lube??

Probably right - thank you!

 

[E-T-M]

Residual case lube??

Thanks aloco - this is probably right. I noticed some of my case cartridges were a bit sticky after cleaning and drying. The residue may have accumulated throughout the session.

 

[E-T-M]

Old solvent

Thanks 243Lapua. I do clean the Chamber quite well after cleaning the barrel but I do my final borescope check with the rod guide still in the Chamber. I'll make sure to remove the boreguide and check with the borescoe that the full chamber is clean next time.

 

[gdbleb]

Clean your dies as well now.

 

[Fuj]

I'll go with a combination of residual case lube / bore
cleaner. One of my last steps in bore cleaning is to run
a chamber mop wet with isopropyl alcohol.

 

[boltfluter]

I'll go with a combination of residual case lube / bore
cleaner. One of my last steps in bore cleaning is to run
a chamber mop wet with isopropyl alcohol.

What Fuj said. Isopropyl alcohol makes for a squeaky clean chamber. Last step I do.

Paul

 

[divingin]

I've gotten the same stuff on cases when I didn't dry the chamber after cleaning. The heat from firing evaporates the volatiles in the solvent, and leaves a brownish, almost grease-like contaminant.

Like JMayo, I spin a dry bore mop in in the chamber as a last step to cleaning (which, as a plus, also avoids false pressure signs.)