New AR15 Build, BCG Hitting Buffer Face – Causing Marring, Need Input

[fiatlux]

Hey guys,

I’ve noticed that my BCG is making contact with the buffer face and leaving some visible marring. The wear isn’t deep, but it’s definitely noticeable and repeatable. This has me wondering if something in my setup is out of spec or needs adjustment.

Parts: 16" Del-Ton Complete Upper(1x9 LW Mid-Length FT Barrel Assembly), AP M4E1 Stripped Lower with AP LPK, AP milspec Carbine Buffer Kit, Toolcraft BCG,

I inititally caused some center marring from me unable to close the upper cause I screwed in the buffer tube one rotation to far in. Then when I was doing some dry firing at home I already noticed the marring on it. Desperately wanting to go out and shoot I kinda ignored it and sent 350 rounds through the gun with no hiccups. No malfunctions at all. Dragging a tissue on the bcg doesn't cause it pickup on any fibers so no noticeable burr. There is that shiny section at the 5 oclock position where I'm suspecting it's making impact.

Photos

Appreciate any insight or experience you all might have. Thanks!

 

[smoothy8500]

The buffer is hitting the retaining pin. The pin hole is drilled in the wrong spot.

 

[Ryan Gosling]

i had this issue before. I removed the buffer retaining pin, its unneccessary to the function of the gun. Otherwise, you can use the offset retaining pin shown above, or confirm that you actually bought a carbine buffer and buffer spring. likewise, you can switch to a completely enclosed buffer system like the armaspec silent buffer or jp silent capture

 

[fiatlux]

If it was the buffer retaining pin wouldn't the damage be closer to the edge itself and kinda banging it in. Here's its a little bit above the edge.

 

[AR15barrels]

I’ve noticed that my BCG is making contact with the buffer face and leaving some visible marring. The wear isn’t deep, but it’s definitely noticeable and repeatable. This has me wondering if something in my setup is out of spec or needs adjustment.

In a properly dimensioned AR, the buffer never leaves contact with the carrier so they do not batter each other.
Where we see battering is when the buffer detent is too far rearward in the lower receiver and that causes the buffer to be held rearward away from the carrier when the carrier is all the way forward.
The battering occurs when the carrier moves rearward and makes contact with the buffer.
The carrier could also be too short and would cause this same problem.

The buffer detent is a convenience part and is not required for the gun to cycle correctly.
The easy fix is to simply remove it and then be prepared to catch the buffer when you disassemble the gun.
There are also offset buffer detents made that you could get and install with the detent forward to let the buffer stay in contact with the carrier.

 

[Deleted member 16735]

If you use an Armaspec or JP SCS and remove the buffer detent you can easily adjust the slack out by screwing in the buffer tube. Buffer detents both super annoying and unnecessary.

 

[smoothy8500]

If it was the buffer retaining pin wouldn't the damage be closer to the edge itself and kinda banging it in. Here's its a little bit above the edge.

It may seem that way, but depending on the angle of the retainer, it can hit anywhere along the edge.

https://www.okshooters.com/attachments/img_1983-jpeg.420422/

 

[fiatlux]

It may seem that way, but depending on the angle of the retainer, it can hit anywhere along the edge.

https://www.okshooters.com/attachments/img_1983-jpeg.420422/

So I removed the buffer retainer, marked the buffer, and cycled it 10-15 times by hand and this was the result. The bottom of the buffer, 6-7oclock position was down which is where it would have been contacting that shiny section of the bcg in the first series of photos...

 

[Walmart_AR15]

Like AR15barrel said the BCG actually will push back the buffer into the tube as the upper is closed. Both remain contact under spring tension. Retainer pin should never touch the buffer when the action is closed. Off spec lower is why those offset pin exist.

If the BCG still hit the buffer without retaining pin, ur BCG is out of spec.

 

[AR15barrels]

So I removed the buffer retainer, marked the buffer, and cycled it 10-15 times by hand and this was the result. The bottom of the buffer, 6-7oclock position was down which is where it would have been contacting that shiny section of the bcg in the first series of photos...

Check your lower receiver to see if the buffer tube is actually square to the top deck of the receiver.
Also look at your carrier to see if the tail is uneven and sharp on the bottom.
Those are the first things that come to mind.
If your buffer tube is tilted down from straight, it will cause the carrier to only bear on the face of the buffer and the carrier will slide up the buffer as the buffer moves rearward and then back down the buffer face as the carrier returns forward.
A sharp edge on the lower 1/4 of the bolt carrier would dig into the buffer if the tail of the carrier is not square.