Chrome Lined Chamber markings on spent cases

[manchuman]

Hello, I recently shot my first .223 reloads through a new upper I recently purchased. It was the second AR Chrome Lined barrel that I have shot and I shot them regularly with my M4 in the infantry. The cases after being fired were covered in what looks like marks from a rough metal finish in the chamber. I have never seen brass expended from a rifle that looks like this whether manual action or semi auto and I have shot, M14, LR308, RRA LAR-15 with Chrome bore and LAR-15 w/o chrome bore as well as numerous military M4, M16, M249 and M240. I haven't encountered it while sifting through military range brass either from all the rifles firing on hand that day. Has anyone seen the type of damage to cases exhibited by this chamber. The only description I can make is that it is rather porous and has a bit of a rough texture to it. Most expended AR brass I am accustomed to has the signature indents from the brass deflector and star chamber. These had those indents plus this porous damage. The loads I shot are minimum charge (10% from max) and was curious if this chamber condition would press out as I raise pressures and break in barrel? Picture attached. Headspace for cases was set with Dillon .223 headspace gauge and I resized with a RCBS small base die. Dimensionally, I did not see any shortcomings in the headspace for the cases or body dimensions as measured before shooting that would have caused issues feeding. I experienced no malfunctions. Headspace and case dimensions for reloads were same as sampled factory Gold Medal match, Lake city and Hornady match prior to shooting.

 

[joustin]

Was there any lube on the brass? Just a WAG, I've seen that before with a pistol barrel

 

[manchuman]

Joustin, do you mean lube? The cases were not lubed. I removed it all after resizing and even removed the oil from the chamber and bore before shooting. I tumbled a couple pieces of the brass for 4 hours to see what it would be like before reloading again. It essentially just removed the carbon and the defects are still there and even more apparent/rough. I was mostly curious if this is a factor from the chroming process and typical and will disappear with time from break in. If not, its probably going back to the manufacturer since they have a lifetime warranty.

 

[Reloadron]

I have seen better and I have seen worse. Are the only fired cases with marks your loads? Have you shot any new fresh factory ammunition? Those cases do not really look all that bad.

OK, new upper so a new barrel and chamber that was freshly reamed. Cleaning the brass will not remove chamber markings, scratches or for that matter minor dings. It will, as you observed, make scratches more visible. That would be expected to my way of thinking. What you are seeing really doesn't surprise me and if it were my rifle wouldn't upset me.

If you have concerns I would just polish the chamber a little. Polish means just that. You do not want a chamber with some sort of mirror finish. You simply want to remove any burrs and minor imperfections left from the reaming process when the chamber was cut. A Google will bring up a dozen methods to clean and mildly polish the chamber. When a cartridge case is fired it does a very rapid expansion and needs to be able to grip the chamber wall. Giving a chamber a mirror or bearing finish will not aid in this process. So you just want to remove the burrs and minor imperfections remaining from the manufacturing process.

Just My Take....
Ron

 

[joustin]

yes i meant lube lol, that was a guess

 

[WestKentucky]

To get a quick break in done you could burn through a lot of steel case crapola ammo. If it's burrs and such the rougher steel cases will smooth it out a bit better, and harder cases SHOULD smooth those things out more quickly, but that's just my thoughts and I have no way of backing that theory up.

 

[243winxb]

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