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 


.....