[arnoob]

Hey all,
I have a question that I know someone on here can answer..
Recently bought an M4 in a private sale..great shape apparently very few rounds through it on initial inspection.. Shoots great but it leaves pretty deep scarring on the cases during cycling.. Is this typical of AR's or should I be overly concerned? Thanks

 

[unclenick]

Welcome to the forum. Rules are to join in and have fun and play nicely with the rest of us kids.

There's scarring and there's scarring. Can you post a photo or maybe better describe what you see?

 

[arnoob]

Don't have a pic on hand but it's deep enough that you can feel them with a fingernail and see them distinctly.. Basically, metal is being removed from the cases..all be it just surface metal..

 

[arnoob]

Also, just for your info.. the Barrel is a custom made Stainless Bull Barrell, 20" that was supposedly recently built and fitted on the rifle. 250 rounds recent according to the seller.. I'm not sure if this could cause sharp burrs etc. on the female star feature at the front of the chamber that would cause scarring.. seems probable to me.. what do ya think?

 

[UnCruel]

My cases all get dented as they bounce off of the brass deflector on their way out.

Is this like a scratch, longitudinally along the case body and maybe the neck? The ejector on the AR is a spring plunger in the face of the bolt. The rim of the case is hooked under the extractor claw. This has the effect of leaning the case in the direction of the ejection port as it is drawn out of the chamber. The body of the case would presumably drag along the edge of the chamber and/or the lugs of the barrel extension (that female star feature). If either of those are sharp, they could presumably scratch away some brass. I'm not sure how much you would have to take off before you could feel it with your fingernail.

 

[unclenick]

First, as you gathered, this isn't what most of us see, but without at least a description of the scratch, we don't even know if it is longitudinal, circumferential or on the body, shoulder or neck. Some detail would be helpful.

If it is a longitudinal scratch on the forward portion of the case body that stops at the shoulder, then UnCruel's explanation seems likely, and you could use a small ceramic triangle or rod stone to just dull the inside corners slightly on the offending lugs. Easier to do with the barrel removed, but if you don't have the tools, you may be able to do enough by feel with the bolt removed. It should need very little much material removed.

 

[Tang]

I experienced the same thing as Uncruel with all 3 of the AR's I had.