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8/9/2025 10:39:21 AM EDT
I recently got a KAC Mod 2 upper and I opened it up to clean it and saw that there were some “swirls” or burnishing or something inside where the BCG sits. I attempted to brush it and CLP it but it stayed.

Is this something I should be worried about? Is the finish done? Anyone else seen this in their Mod 2? Thanks.

Attached File


Attached File
8/9/2025 11:19:20 AM EDT
[#1]
That looks a good bit like the dry film lube that some companies apply to the inside of an upper.
WTB: Steel Bodied Surefire Trainer
8/9/2025 11:21:54 AM EDT
[#2]
Dry film lube.

My guess is you're the guy who bought the upper the seller posted about in the AR section that I just responded to .

I've had a few that look exactly like that, enjoy the upper!  Its fine.
8/9/2025 11:40:24 AM EDT
[#3]
lol, I basically just wanted to make sure I didn’t need to refinish it in the future. I did try scrubbing it out with a brass brush but the swirls or whatever it’s called stayed.
8/9/2025 12:10:52 PM EDT
[#4]
Quote History
Originally Posted By LoDie:
lol, I basically just wanted to make sure I didn’t need to refinish it in the future. I did try scrubbing it out with a brass brush but the swirls or whatever it’s called stayed.
View Quote

It's not something you can "scrub" out. It's just how the finish was applied. As long as it's smooth, it's fine. Don't overthink it.
8/9/2025 12:45:56 PM EDT
[#5]
Quote History
Originally Posted By LoDie:
lol, I basically just wanted to make sure I didn’t need to refinish it in the future. I did try scrubbing it out with a brass brush but the swirls or whatever it’s called stayed.
View Quote


Yeah....don't do that next time
8/10/2025 10:04:25 AM EDT
[#6]
Originally Posted By LoDie:
I recently got a KAC Mod 2 upper and I opened it up to clean it and saw that there were some “swirls” or burnishing or something inside where the BCG sits. I attempted to brush it and CLP it but it stayed.

Is this something I should be worried about? Is the finish done? Anyone else seen this in their Mod 2? Thanks.

https://www.ar15.com/media/mediaFiles/387582/IMG_4515_jpeg-3603359.JPG

https://www.ar15.com/media/mediaFiles/387582/IMG_4514_jpeg-3603360.JPG
View Quote


Its fine, most of mine including sr25 uppers have it.

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