My son just got an AR pistol upper and we were putting sights on it last week.  I just got around to cleaning the brass and I found these marks on a lot of the brass that I've never seen before.  I think these were shot through his upper, it was a pile of brass with maybe 40% percent of it shot through one of my rifles or random range pick ups.  However he was shooting factory FC 223 Rem rounds and that's the only thing I'm finding the marks on.  I've asked him to see if those marks are there in the box, but he's at work so it'll be a while before I get that answer.  I'll also check the headspace on it when he brings it over next time.

Apologies for the iphone pics, but that's all I have.  I don't know why they are rotated 90 degrees counterclockwise.  If you right click them and view image, they're the right way on my PC.

Above the red line on each case there is a horizontal 'scratch' that you can feel with your fingernail.  This 'scratch' goes about 1/3 around the case.  You can also feel it on the inside of the case with a dental pick.  The left most case also has a vertical split right on the shoulder starting about .020" below the shoulder and going a little more than halfway to the neck between the two red dots.



I sawed two of the cases apart.  #1 was the left most case, I don't know which of the other three cases #2 is.  Case number one I did not saw through the scratch.  I wanted the shoulder issue intact.  Case #2 I went directly through the center of the scratch.



I don't think the 'scratch' going around the case is a crack.  I stoned the edge of the piece I sawed out of case #2 to polish it up a bit and looked with a 20x loupe.  I also tried to bend the case apart there and it wouldn't budge.  But you can still see the line and feel it on the inside of the case.

The crack on the shoulder of case #1 going up to the neck is a crack.

The gun is over gassed, it's ejecting the empties to 1 o'clock and there is a pretty good extractor mark on the rims.  A few of the cases have a slight bend at the extractor but nothing close to ripping the rim off.

So do you think this a rough chamber, headspace issue or a FC brass manufacturing issue?  Send the upper back to the manufacturer or keep shooting it with steel cases?  I'm not going to reload these.

TIA
TripletDad

I got a friend who has a 380 pistol that does the same thing, a line just below the case mouth. I told him to get the gun checked out by a gunsmith.

Seems like the chamber may be out of spec

Texting with my son, he did not find any of the scratches on the unfired factory ammo.  He can't see or feel anything wrong in the chamber either.  Next time he's over, he'll bring it and I'll check the headspace.

Anything else that could be causing this?

If the chamber is oversized by a couple thousandths, he's not going to be able to feel it with his finger.  

Some guns leave marks on the brass and function fine.  I'd ask the barrel mfr for input.

^ That's a good idea.

More importantly OP, how's it shoot?

What is the barrel/gas system lengths?  7-8" barrels with pistol length gas systems are know for being over gassed to the point on near violently excessive extractions due to the chamber pressures at the time the bolt unlocks.  That said.  Unless the casings are contacting the ejection port upon ejection, I'd say there is a defect in the chamber.  That may or may not be of concern.  If it doesn't cause the cases to stick or case ruptures I wouldn't worry much beyond polishing the chamber.  

Good luck and let us know the results of checking the headspace.

The feeling it I was referring to was with a dental pick to see if he could find a rough spot, ridge or valley in the chamber.  He said he couldn't.  I would have thought there was going to be some raised metal.

Every one of the approx 125 FC 223 Rem head stamped cases have the issue.  No other head stamp does.

There we no issues we noticed while shooting and putting the sights on it.  Only thing we commented on was it was over gassed going to 1 o'clock and the case rims were more buggered up than they normally are.

It shot very well I thought for a 7" barrel.  My son moved his 1-6x Strike Eagle on it and he was hitting an 10" square steel at 396 yards with it about 1/2 the time.  Of course it was supported off the bench doing that and I was calling shots for him since we'd just gotten done playing with our precision rifles.

Having never seen a chamber reamer in my life, could that be some type of tooling mark?  They seem to be consistently located relative to the extractor mark.  If you're looking at the back of the case with the extractor mark at 3 o'clock, the 'scratch' starts around 6 o'clock and goes up to 10 o'clock or so.  I don't see how feed ramps or anything like that could make a scratch like that going around case.

If you want to visually inspect the chamber...go to amazon, and buy an "endoscope" for your smart phone.

It must have a 5.5mm dia head (or smaller) to fit down the barrel.






endoscope on amazon




_

Reamer mark.
I'll see your one ring, and raise you a couple dozen.

Seems as if there might have been some chatter when reaming the chamber.

Ouch.  Is that a home made barrel, or storebought?

The barrels were bought direct from the maker, one was a GM and the other a BA. And I had a third barrel that looked the same, just couldn't find the pics of that one.
Both companies bent over backwards to make things right and new barrels were sent to me.

Is the brass raised or depressed at the mark?

Raised would be chatter or a scratch during reaming.

Depressed might indicate violent extraction and stretching of the brass.