Updated see last post - How can I fix this ejection mark problem on my AR?

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PigPknHeat

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The chamber side of the "Star bolt lock" (not sure what the proper name is) seems to be beating up my brass pretty good. Some cases are trashed after one firing because the scratch is so deep I'm afraid to reload it thinking it might split. I tried to illustrate with some photos below. Would a few swipes of some 2000 grit sand paper take care of the issue? What else might work?

Top pic is of the case mid extraction, followed by that same case with new scratches from the "test" and a deeper one from live fire (which in the middle of the new scratches), and last a few fired cases.





 
Last edited:
I've reloaded brass with scratches like that. If you are concerned I would not mess with the barrel extension but just try to make extraction less forceful somehow (e.g., playing with the buffer weights).
 
Ok so you have a pretty sharp edge on the locking lugs.
I guess you could call them the feed edge of the locking lugs.
Could you take a dremal with a polishing pad a just take down those edges a bit?
How's the ejector plunger and and spring. Do you have any type of extractor up grades?
I have my "varmint" rifle out I will give mine a look to see how it looks in that area.
 
If there are any visible burrs in the locking chamber, you wouldn't hurt anything by sanding them off. Try some 600gr rolled around a small Allen key and work at it a bit. Don't take much off, just enough to remove the knife edge.

What angle is it ejecting?

Like mac1911 said, it could be extractor related. Or ejector. I'll also check mine and see if the shell is dragging like that mid extraction.
 
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Doogz said:
If there are any visible burrs in the locking chamber, you wouldn't hurt anything by sanding them off. Try some 600gr rolled around a small Allen key and work at it a bit. Don't take much off, just enough to remove the knife edge.

What angle is it ejecting?

Like mac1911 said, it could be extractor related. Or ejector. I'll also check mine and see if the shell is dragging like that mid extraction.
Click to expand...

Angle depends on load... most id say 2 to 3 o'clock sone at 5

- - - Updated - - -

icyclefar said:
Have you checked the fit of the bolt in the carrier, the gas key, and rings?
Click to expand...

Not sure how to test fit... it stands without collapsing.

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Doogz said:
Do you have an extra bolt laying around to try?
Click to expand...

No
 
Basically take your bolt out and place a case under the extractor and "force" the case straight and push in the ejector. You will see there is some pretty stout tension there. See if you feel anything that's tight or binding in that movement.
No matter what you do your case is going to "hit" the barrel extension/locking lugs.
You need to see if it is just a really sharp edge on those locking lugs at 3 o'clock. The back side is where it's picking up the damage.
Or for some reason the extractor/ejector is applying to much force. Do you see any extractor marks in the extractor groove ?
Does the damage vary with your loads.
 
There are some pretty visable burrs on the lip of the slot at the 2 o'clock postion.
You couldn't hurt much if you carefully removed them with a small jewlers file.
 
mac1911 said:
Basically take your bolt out and place a case under the extractor and "force" the case straight and push in the ejector. You will see there is some pretty stout tension there. See if you feel anything that's tight or binding in that movement.
No matter what you do your case is going to "hit" the barrel extension/locking lugs.
You need to see if it is just a really sharp edge on those locking lugs at 3 o'clock. The back side is where it's picking up the damage.
Or for some reason the extractor/ejector is applying to much force. Do you see any extractor marks in the extractor groove ?
Does the damage vary with your loads.
Click to expand...

I will test that tomorrow but I know exactly where it is happening just can't figure out the right fix (have not tried anything yet). IMR4198 loads for example extract with the least force. I have a rifle length buffer and carbine length gas, so those loads cycle fine but defiantly have low felt recoil. My thoughts are that those are getting the worst of it since the heavy recoil would have less drag time on the lugs.
 
load or precieved recoil is not the problem...im shooting some pretty stiff loads and I have to blacken the case with a sharpie to see the marks left by the locking lugs.
 
mac1911 said:
load or precieved recoil is not the problem...im shooting some pretty stiff loads and I have to blacken the case with a sharpie to see the marks left by the locking lugs.
Click to expand...

I know im just saying each one leaves more or less marks... still marks... im gonna try to polish it this weekend
 
PigPknHeat said:
I know im just saying each one leaves more or less marks... still marks... im gonna try to polish it this weekend
Click to expand...

Is it all the same lot of brass? Some brass maybe softer than the others.
Playing with some empty cases the other night I get the same two drag marks you get but only on the necks. I see no signs of should contact like you have. This makes me think the extractor or ejector in fashion is putting a bit more power to to case earlier .......if that makes sense?
 
IDK, maybe it's just me but I don't see a real problem here, brass gets muffed up sometimes. My 6.5 Grendel brass get's scratched up pretty good during the feed cycle as well as some of my 5.56 guns, some are worse than others. But again I'm no expert.
 
1903Collector said:
IDK, maybe it's just me but I don't see a real problem here, brass gets muffed up sometimes. My 6.5 Grendel brass get's scratched up pretty good during the feed cycle as well as some of my 5.56 guns, some are worse than others. But again I'm no expert.
Click to expand...

Some of the real bad scratches are deep... i chucked one up to see how much i scould sand off till it was gone and i got pretty much down to the end before it was gone... then the case cracked as i was putting a little pressure on it so its pretty damn deep and would have probably split
 
Well I took some 2000 grit sandpaper and wrapped one layer around a 1/4" oak dowel and took my time with it but I'm pretty sure I fixed it. Simulated extraction slow and fast leaves no marks, cant wait to test at the range. I wish I did this 1000cases ago. The only way I can get a case to show marks is if I push in and out several times just before the case gets thrown out.
 

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