Odd wear/mark(?) in upper receiver

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[ARCHIVED THREAD] - Odd wear/mark(?) in upper receiver

Posted: 9/22/2020 12:09:32 PM EDT

When cleaning a new AR I noticed this odd row of square(ish) marks inside the upper receiver. I honestly can't remember if it was there before firing (maybe 100 rounds have been through it). Please see image. What am I looking at here?

Posted: 9/22/2020 12:15:54 PM EDT

[#1]

ETA: Here is your image.

When you post an image, link directly to the image. Not the page it is displayed on, but the image itself.

Posted: 9/22/2020 12:38:01 PM EDT

[#2]

Thanks.

Posted: 9/22/2020 7:07:39 PM EDT

[#3]

Cam pin?

Posted: 9/22/2020 7:44:39 PM EDT

[#4]

Uneven machine marks, made during manufacturing.
Caused by tool run-out (slight wobble), and too fast of feed rate.
Normally only a cunt hair or less in depth.
When final finish is made, become invisible, but as moving parts slide across it, the finish wear on the high points becomes visible.

Doesn't hurt anything....

Posted: 9/23/2020 11:14:50 AM EDT

[#5]

Quote History

Quoted:
Uneven machine marks, made during manufacturing.
Caused by tool run-out (slight wobble), and too fast of feed rate.
Normally only a cunt hair or less in depth.
When final finish is made, become invisible, but as moving parts slide across it, the finish wear on the high points becomes visible.

Doesn't hurt anything....

View Quote

so about .003 deep

Posted: 9/23/2020 3:37:22 PM EDT

[#6]

Thanks, guys.

[ARCHIVED THREAD] - Odd wear/mark(?) in upper receiver

AR-15 » Maintenance & Cleaning

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