Barrel Extension Detailing

[BeeKay]

I'm building an upper - This is only my second

My first build was pretty simple, and I had no problems
That was around 2019 - It was luck

I just got some parts and put them together, and it didn't give me any problems,

Shortly afterward,  I wanted to try a different upper,  and I wasn't as lucky the second time.
I didn't bother to troubleshoot it until now, because I have one that works,  so why bother ?

Anyhow it's time to troubleshoot that, because I'm not as fortunate on this upper build.
I have feed hangups and when I look at the lugs on the barrel extension, I see copper shavings there.
In addition to the copper shavings, there are scratches in the bullets as a result of feeding.

For starters - I'll ask if there's a You Tube channel that can be recommended ?
I started watching Sons of Liberty Gun Works
Because he appears to specialize in AR builds.
But I'm open to further suggestions,
since YT doesn't like to show very much when it comes to gunsmithing.

I can show some pics of the scratch pattern on the copper jackets of the bullets,
If that would be helpful.
OIr if someone has some explanation that's better than a video, I'm open for that.

Thank you very much in advance 


.....

 

  

[98Z5V]

How many total round through the gun? 

[BeeKay]

15 hours ago, 98Z5V said:

How many total round through the gun? 

I am using a bolt and a barrel that are leftover parts from an earlier build 
It's a KAK .308 Barrel and Bolt 
Which I am now putting onto a BCA Sidecharging Upper
But the Bolt / Barrel combo has about 150 rounds through it
The rest of the combo - Including the BCG and Upper & Accessories have never been fired.

Thanks for your help

 

Edited March 6 by BeeKay

[BeeKay]

15 hours ago, 98Z5V said:

How many total round through the gun? 

I think there may be some burrs or sharp edges on the lugs of the barrel extension,
As well as the feed ramps showing a slight bit of overhang where it shouldn't be .
The edge of the barrel extension feed ramps is about .005" proud of the ramp edge on the housing.

[BeeKay]

17 hours ago, 98Z5V said:

How many total round through the gun? 

This video shows the issue
He isn't permitted to show the actual process,
because of YT guidelines.

Also I get some chips from a burr or sharp edge  on the lugs of the extension
scratching the jacket on the bullets when I feed them.

It seems like possibly there'd be a general deburring process that I can do to solve that problem as well.

Ideas welcome - Thanks 

 

 

[shooterrex]

Take some pics and post them.

[BeeKay]

10 hours ago, shooterrex said:

Take some pics and post them.

OK

Prolly Saturday afternoon
Ever watch SOTAR - That's the channel in the video I posted
He gets into some things that I wasn't familiar with, but makes sense

[98Z5V]

On 3/5/2026 at 9:12 PM, 98Z5V said:

How many total round through the gun? 

@BeeKay, let's go back to this, too.  How many total rounds have been fired through this gun that's having this issue?

[98Z5V]

On 3/6/2026 at 12:20 PM, BeeKay said:

But the Bolt / Barrel combo has about 150 rounds through it

Okay, I found it ^^^

At 150 rounds, you're still breaking that gun in.  Keep shooting it, don't worry about marks on the brass on a brand new barrel, and let us know what it's doing at about 300 rounds - alot of the stuff you're seeing now, is going to stop happening as you break that gun in. 

[BeeKay]

On 3/7/2026 at 4:11 PM, 98Z5V said:

Okay, I found it ^^^

At 150 rounds, you're still breaking that gun in.  Keep shooting it, don't worry about marks on the brass on a brand new barrel, and let us know what it's doing at about 300 rounds - alot of the stuff you're seeing now, is going to stop happening as you break that gun in. 

It looks like the copper shavings are the result of an unfired round being ejected and the copper of the jacket being dragged over the lugs with the pressure of the ejector pushing it as it moves back.

Not a problem

Thanks, I'll be back if there's anything else

Edited March 10 by BeeKay