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Author Topic: AR15 BC Brass Markings  (Read 654 times)

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Online AnjaP

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AR15 BC Brass Markings
« on: January 20, 2018, 09:16:44 PM »

Brand new AR15 upper, noticed after first range trip what appears to be brass markings on underside of bolt carrier.  Can also see markings on spent casings so I’m 99% sure I have the Bolt Carrer rubbing the brass.  Firearm functions fine, no issues clambering, ejecting or moving the bolt what so ever, but being new to AR’s I can’t help but wonder is this normal?

Thanks




Online AnjaP

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Re: AR15 BC Brass Markings
« Reply #1 on: January 20, 2018, 09:21:35 PM »



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« Last Edit: January 20, 2018, 09:22:18 PM by AnjaP »

Online MikeScouter

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Re: AR15 BC Brass Markings
« Reply #2 on: January 21, 2018, 10:20:56 AM »
The round being stripped, chambered and then ejected should only have contact with the bolt face, so it would have to be contact with the remaining rounds in the magazine. I would start by trying a different magazine. It’s possible the current mag seats higher in the mag well or the mag may be worn, have bent lips or allow the round to sit higher in the magazine. What type of magazine was this?
Mike

Online AnjaP

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Re: AR15 BC Brass Markings
« Reply #3 on: January 21, 2018, 10:44:42 AM »
P and Hex Mags.  Both brand new.  Maybe the spring just needs to break in a bit?

Online edgephoto

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Re: AR15 BC Brass Markings
« Reply #4 on: January 21, 2018, 11:02:05 AM »
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P and Hex Mags.  Both brand new.  Maybe the spring just needs to break in a bit?

No.

What lower are you using?

Online AnjaP

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Re: AR15 BC Brass Markings
« Reply #5 on: January 21, 2018, 02:14:26 PM »
Colt SP1.  Every other part of rifle is factory new (and installed by me) so maybe I dicked something up?

Online Silverbear

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Re: AR15 BC Brass Markings
« Reply #6 on: January 21, 2018, 02:37:35 PM »
Brass marks like those are perfectly normal.  As the bolt travels to the rear, the rounds in the magazine are pressed up against it by the magazine spring so brass will rub off on the underside of the bolt.  As the bolt gets worn in the marks will diminish as those surfaces get polished by usage.  A new bolt will have a slightly rough finish, so it will collect a bit more brass.
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Re: AR15 BC Brass Markings
« Reply #7 on: January 21, 2018, 06:44:26 PM »
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Brass marks like those are perfectly normal.  As the bolt travels to the rear, the rounds in the magazine are pressed up against it by the magazine spring so brass will rub off on the underside of the bolt.  As the bolt gets worn in the marks will diminish as those surfaces get polished by usage.  A new bolt will have a slightly rough finish, so it will collect a bit more brass.

What he said
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