This is my first AR and the first time shooting one.  I just broke in the barrel (Stainless Steel Barrel)  After I got home I was checking out the cases and noticed that all 20 of them had a scratch down the neck, and a dent on the collar (whatever you want to call it).  

Is this normal?  It seems to be doing it when it is ejecting the case because the neck is burnt and the scratch is fresh brass.  

http://home.comcast.net/~blacktbird96/case.jpg

-J

Looks to me like those scratches are from the bullet passing from the magazine and kissing the feed ramp as they enter the barrel. I had dents similar to those from a dirty chamber walls.

mine look the same

Dents in brass is not normal.

Sorry, Tweak, but I can't agree that--in a properly cycling rifle--dented brass is normal and acceptable.  I know it happens in some rifles, but that doesn't mean it's supposed to.

20 rounds looked like that?  Were you using 20 Round Magazines?  

Quoted: if the scratch is on the same side of the case as the mark from the extractor is on the extractor groove it's normal.

The scratch is on the same side as the extractor marks.

Quoted: 20 rounds looked like that?  Were you using 20 Round Magazines?

I was using a 30 Round mag with 5 rounds loaded at a time.

The scratches looks to me as if they are from the feeding of the rifle.

Quoted: dude the design drags the fired case alongside a steel extension, how does it not scratch? hell the cases get scratched just coming out of the mag

+1

Looking at the top picture and the scratch to the right, looks like it was caused while being extracted, not during the feed...  You might want to inspect the chamber for burrs too...

ETA:
The dent on the collar is from the empty casing smacking up against the shell deflector after being ejected...

Look at the top case; you will see that the scrap is being caused during the ejection pull since the end of scrap is the area with the build up still left, and the sharp edge, the start point.

As for what is causing it, the lug tip at the fore most ejection port side of the receiver extension has a sharp end bur, and as the case is being withdrawn from the chamber (chamber no longer supporting the case*), the case is being kicked to this lug and scrapped down it on the ejection.

*When the case is withdraw enough to leave the just the neck section in the camber, the lug bur makes contact at the beginning of the shoulder, then as the neck clears the chamber, the case is allowed to even more misalign with the bore line (90* off the bolt face), to allow the lug to dance off the spent case a third time at the neck (think of it as chatter when machining).

My new Stag Arms leaves the very same dents, since there on the extracter side of the case I'm assuming there hitting the deflecter pretty hard. I've had no problems during break in with over 400 rnds fired so far. Next time I shoot I'll stand back and see if there ejecting properly.