Wear marks on buffer face

[Glock9mm1990]

I didn't notice at first but I recently have noticed some wear marks on one of my ARs on the face of my buffer around the edge of the buffer. The rifle is a complete BCM upper with an Aero Pricision lower but with all BCM lower parts. This is my second build. When I manually cycle the rifle the marks will appear around the buffer retaining pin.
Attachment 44862
When I slowly mate the upper and lower I can see the BCG push the buffer back off the retaining pin like it should but the marks will still appear on the lower edge were the buffer retaining pin is.
Attachment 44868
I know my Colt 6920, a Bushmaster and my other AR build doesn't do this. So I decided to swap uppers, buffers and springs, and mix BCG's to see if I can isolate it and I found that it was one BCM BCG that would leave the marks on the edge of the buffer face but when I put a second BCM BCG or even a Bushmater BCG then no marks. So Im thinking a bur is on the end of one of my BCM BCG maybe? Any corrective action needed? I just hope I didn't missed something like maybe its an out of spec lower worst case scenario.

[Clint]

Yes,

A burr on the BCG will do this.

Good job diagnosing this, BTW.

The relief slot for the buffer retainer at the bottom rear of the carrier can have sharp edges.

You can lightly hit it with a stone to knock the corners off.

[tom12.7]

Make sure that the carrier takes the preload of the action off the detent with the upper and lower assembled. It's easy to mistake preload when pivoting on the front pin. Verify that the carrier fully locked takes the preload off the pin when sliding the upper and lower halves into assembly held together without the take down pins engaged. There should be no contact between the retention pin with the buffer when assembled.

[Glock9mm1990]

Make sure that the carrier takes the preload of the action off the detent with the upper and lower assembled. It's easy to mistake preload when pivoting on the front pin. Verify that the carrier fully locked takes the preload off the pin when sliding the upper and lower halves into assembly held together without the take down pins engaged. There should be no contact between the retention pin with the buffer when assembled.

I'll try this when I get home from work.

[Lost River]

So this is not relevant to the topic at hand, but I figured some might think it is funny.


When I read the thread topic, I initially thought it said:

"Wear marks on butter face."

[jstalford]

So this is not relevant to the topic at hand, but I figured some might think it is funny.


When I read the thread topic, I initially thought it said:

"Wear marks on butter face."

Came here to post this. Lol.


Sent from my iPhone using Tapatalk

[Glock9mm1990]

Just got home work, and I was able to verify that the BCG does in fact take the preload off the retaining pin. Also I held up both my BCM BCG to the light and I was able to see two rough edges that visibly were sticking up just ever so slightly at the tip of the ratianer relief area of the carrier(don't know the actual name)of the one that was suspect. After that I took the buffer with the marks on it and I changed the orientation of it to a side that didn't have marks yet and put the carrier with the burs in it and racked one time. Low and behold there was two marks one on the left and one on the right of the retaining pin further confirming that its not the retaining pin itself nor the lower or upper.

It is a bit suprising that a BCG from BCM would have burs on it given their stellar reputation for quality. But I'm not knocking them at all I know mistakes can happen with any company and I will continue to be a BCM fan and recomend to to everyone I know. I basically answered my own question but I figured I'd share this hoping it would be helpful to anyone else who might have a similar issue.

[Iraqgunz]

You would be misled or mistaken to think that companies examine every single part for stuff like this. It may be unsightly, but it's ging to have very little impact on function.

Just got home work, and I was able to verify that the BCG does in fact take the preload off the retaining pin. Also I held up both my BCM BCG to the light and I was able to see two rough edges that visibly were sticking up just ever so slightly at the tip of the ratianer relief area of the carrier(don't know the actual name)of the one that was suspect. After that I took the buffer with the marks on it and I changed the orientation of it to a side that didn't have marks yet and put the carrier with the burs in it and racked one time. Low and behold there was two marks one on the left and one on the right of the retaining pin further confirming that its not the retaining pin itself nor the lower or upper.

It is a bit suprising that a BCG from BCM would have burs on it given their stellar reputation for quality. But I'm not knocking them at all I know mistakes can happen with any company and I will continue to be a BCM fan and recomend to to everyone I know. I basically answered my own question but I figured I'd share this hoping it would be helpful to anyone else who might have a similar issue.

[sidewaysil80]

Huh, I thought that wear was normal.

Ironically I am experiencing the same issue with my 10.5" and Vltor A5H3. Can someone go into more detail in explaining the carrier/preload aspect to look for?

[feraldog]

could it be caused by the same problem i had? (i found a solution)

https://www.m4carbine.net/showthread...amage-solution