Blue Plastic-Like Residue Seen in Borescope

Bidwell

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Aug 16, 2024
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41
Hi, got a borescope and started looking at my rifle today. I noticed right away that there's this blue plastic-like residue near the crown. No where else. I use Barnes TTSX 130 grain 308 projectiles with the dark blue polymer tip. Is this what that's from? I've read that these tips don't melt so not sure what's going on. Getting good accuracy so it doesn't seem to be effecting much but would just like to know for sure what it is. I attached an image, any ideas?1735431160010.jpg
 

AZ_Hunter

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May 1, 2024
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Copper oxidizes blue. Look at an old crusty penny or copper piping… also why patches with copper solvent will come out blue.
 
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Bidwell

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Aug 16, 2024
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Copper oxidizes blue. Look at an old crusty penny or copper piping… also why patches with copper solvent will come out blue.
Wow, well that thought definitely crossed my mind. Just was surprised how crusty and plastic like it looked. Must be it. Here's another picture just from my phone
 

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AZ_Hunter

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You should see what forms on my high volume AR suppressor adapters. Blue chunks.
 

TaperPin

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Jul 12, 2023
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Wow, well that thought definitely crossed my mind. Just was surprised how crusty and plastic like it looked. Must be it. Here's another picture just from my phone
Somewhere I read an article about the chemistry of burning smokeless powder - there are all sorts of chemical residue, many of which are acidic, so that helps explain why copper turns green so quickly even in a dry climate.
 

nosualc

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Joined
Jan 1, 2025
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They're the only way to really know if your cleaning regime, ideally minimal, is really working.

Now that they're so cheap, it's a worthy investment even for moderately serious shooters.
 
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