What would cause this mark on case

dkamen2

dkamen2

Private
Minuteman
Mar 10, 2020
12
2
#1
Hello

I have problem with marks on my lapua cases on 308 win, no stiff bolt on action or other signs of overpressure. I have around 800m/s with 175gr lapua scenar L bullets, N140 powder, 28inch barrel length. I have the same problems with factory ammo, more on pictures.
 

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#3
Looks like extractor swipe. It is not uncommon to see. Being no gunsmith I cannot tell you why some rifles do that when not as a sign of pressure but I suspect it is a mechanical condition and not pressure if it also exhibits with factory ammo
 
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#13
If that is happening with factory ammo, i would look at the chamber next for a possible issue. At 2600 fps, 28 inch barrel for a 175gr bullet. Its hard to think thats its a over pressure issue with factory ammo as well.

Maybe a bad chamber?
 
#14
308pirate said:
@dkamen2 The tip of the ejector leaves that mark as the bolt is rotated during opening. Why do you think it's a problem?
Click to expand...

The tip of the ejector is leaving that mark? I've never heard of the tip leaving a mark. That looks like a pressure problem to me.

Looks like a classic half moon from overpressure of brass that flowed into the ejector hole. Pressure was high enough to push brass pretty far into the ejector pin hole on most of the brass. The bright smears are from when the bolt rotated past the locking lugs, before it hit the extraction cam. The bolt rotates but the brass does not because it is still stuck in the chamber before primary extraction. The rotating bolt scrapes the high spot in the brass that was pushed into the ejection hole. The smear doesn't always happen, and it looks like a couple were over pressure but didn't get the smear. At least, that's what I've seen. But, on my Nucleus action with mechanical extractor, the brass gets pushed into a slot, which then smears it if it were pushed in far enough.

Primers flatten out most of the time in my rifle, though they didn't here.
 
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#16
hereinaz said:
The tip of the ejector is leaving that mark? I've never heard of the tip leaving a mark. That looks like a pressure problem to me.

Looks like a classic half moon from overpressure of brass that flowed into the ejector hole. Pressure was high enough to push brass pretty far into the ejector pin hole on most of the brass. The bright smears are from when the bolt rotated past the locking lugs, before it hit the extraction cam. The bolt rotates but the brass does not because it is still stuck in the chamber before primary extraction. The rotating bolt scrapes the high spot in the brass that was pushed into the ejection hole. The smear doesn't always happen, and it looks like a couple were over pressure but didn't get the smear. At least, that's what I've seen. But, on my Nucleus action with mechanical extractor, the brass gets pushed into a slot, which then smears it if it were pushed in far enough.

Primers flatten out most of the time in my rifle, though they didn't here.
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I load couple ammo for test to 750m/s, the marks on cases are the same, i really dont know what happens... no flatten primers, no heavy bolt and the rifle are grouping very good, first picture on 300m, second picture 200m
 

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#17
Just for kicks and giggles, load up a few rounds at the lightest powder load in your manual and see if you have the same marks. If it goes away, you know you have a pressure issue.
 
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#19
Average guy said:
Try removing the ejector and check for burrs on both the ejector and the bore edge it fits in. Had a similar issue with a 700 Remington. After removing a very small burr problem solved.
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I polish the whole surface a couple of days ago, but i did not see any bumps on surface. I must fire couple bullets and i will see if its beter
 
#20
Average guy said:
Try removing the ejector and check for burrs on both the ejector and the bore edge it fits in. Had a similar issue with a 700 Remington. After removing a very small burr problem solved.
Click to expand...
I polish the whole surface a couple of days ago, but i did not see any bumps on surface. I must fire couple bullets and i will see if is
 
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#21
Did you polish before or after it left the marks?

Does the half moon stand higher than the rest of the brass? Looks like at least one shows a half moon without the smear. Others show part of the mark without the smear. Using your fingernail is it higher?
 
#23
hereinaz said:
Did you polish before or after it left the marks?

Does the half moon stand higher than the rest of the brass? Looks like at least one shows a half moon without the smear. Others show part of the mark without the smear. Using your fingernail is it higher?
Click to expand...

half moon is not higher then brass
 
#25
If the moon shape on the brass matches the ejector on the bolt face that should point you in the right direction. Overpressure-possibly. Dirty chamber -also possible. I’ve had “slippery” brass show over pressure signs, both nickel plated as well as oil on the chamber wall.
 
#26
AKMarty said:
If the moon shape on the brass matches the ejector on the bolt face that should point you in the right direction. Overpressure-possibly. Dirty chamber -also possible. I’ve had “slippery” brass show over pressure signs, both nickel plated as well as oil on the chamber wall.
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The moon shape on brasses is the same as ejector
 
#27
This is a curious thing.

Have you done anything to your chamber? Does the ejector have a burr? How much did you take off when you polished the bolt face? Why did you polish the bolt face?
 
#28
Like dave Tooley said, it is a pressure sign.
Could be several things.
thick brass. I have seen thick brass cause over pressure on loads that should be mild.
Short throat. Sometimes, mass produced rifles end up with short throats, causing pressure issues with loads that are saami length.
 
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#29
Thick necks, Thick walls reducing volume, lubed cases or chamber, hot lot of powder, sharp corner or burr on ejector hole, tight bore, carbon ring, case doughnuts, short throat/jamming bullets, longer bearing surface on the bullet than what the load data was set for, Vitavouri powder exposed to moisture....
 
#31
hereinaz said:
This is a curious thing.

Have you done anything to your chamber? Does the ejector have a burr? How much did you take off when you polished the bolt face? Why did you polish the bolt face?
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No i didn t do anything to my chamber, this is happens from the beginning when i buy new rifle. I polish bolt face just because i saw if there was any bad surface or somethink like that.
 
#32
The marks are definitely not from the pin itself.

Something is causing brass to flow into the ejection hole and then it is getting scraped before primary extraction starts.

If the loads are mild, then there is something else going on that causes that phenomenon. Primers are still round, so it is a sign that other issues might be going on.

Try factory loads, and if they do it, then it has a problem and should go to someone.
 
#33
hereinaz said:
The marks are definitely not from the pin itself.

Something is causing brass to flow into the ejection hole and then it is getting scraped before primary extraction starts.

If the loads are mild, then there is something else going on that causes that phenomenon. Primers are still round, so it is a sign that other issues might be going on.

Try factory loads, and if they do it, then it has a problem and should go to someone.
Click to expand...
OP stated the problem also occurs with factory ammo.
 
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#35
Poor primary extraction?

Could any gunsmiths elaborate if that can cause ejector swipes even though pressure is normal?

I have a 6.5-284 rem700 that was "trued" and there is a gap between the bolt handle and the receiver. From what I have been able to read up on is that when the bolt lugs are trued or lapped that increased the distance between the bolt handle and receiver thus losing the "primary extraction" of the case during initial bolt lift. In this case having the bolt re-timed is the remedy.

Others thoughts on this?

I am in the exact same situation and just have not sent the action in to have the bolt re-timed or looked at by a reputable smith yet.
 
#36
Have you check the OAL on the ammo? Saw a case of this "brass abuse" just this week at the range where I RO. Turned out the Fiocchi loads (.308/150 grn) the shooter had just bought were seated too long and the projectiles were jamming into the lands.
 
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#37
Niznac said:
Poor primary extraction?

Could any gunsmiths elaborate if that can cause ejector swipes even though pressure is normal?

I have a 6.5-284 rem700 that was "trued" and there is a gap between the bolt handle and the receiver. From what I have been able to read up on is that when the bolt lugs are trued or lapped that increased the distance between the bolt handle and receiver thus losing the "primary extraction" of the case during initial bolt lift. In this case having the bolt re-timed is the remedy.

Others thoughts on this?

I am in the exact same situation and just have not sent the action in to have the bolt re-timed or looked at by a reputable smith yet.
Click to expand...
Not being able to pull the case out of the chamber due to lack of mechanical leverage is not the same thing as brass material flowing into other cavities. Could have similar symptoms in that brass is hard to get out but the extractor wont cause high enough pressures to deform metal.
 
#38
Niznac said:
Poor primary extraction?

Could any gunsmiths elaborate if that can cause ejector swipes even though pressure is normal?

I have a 6.5-284 rem700 that was "trued" and there is a gap between the bolt handle and the receiver. From what I have been able to read up on is that when the bolt lugs are trued or lapped that increased the distance between the bolt handle and receiver thus losing the "primary extraction" of the case during initial bolt lift. In this case having the bolt re-timed is the remedy.

Others thoughts on this?

I am in the exact same situation and just have not sent the action in to have the bolt re-timed or looked at by a reputable smith yet.
Click to expand...
There needs to be some gap there, but it is possible to remove too much material from the lugs, and lug abutments in the receiver, to remove any primary extraction. Most remington’s are already limited in that area. Like spife said though, won’t cause ejector marks.
 
#40
It doesnt really look like pressure pushing material into the hole. more like there is a bur or sharp edge on one side of the ejector hole scraping on extraction.

If it were me I would take the ejector out and hit the hole edges with something like 320 sand paper or small abrasive stone.
 
#41
2aBaCa said:
It doesnt really look like pressure pushing material into the hole. more like there is a bur or sharp edge on one side of the ejector hole scraping on extraction.

If it were me I would take the ejector out and hit the hole edges with something like 320 sand paper or small abrasive stone.
Click to expand...

Easy enough to do. I assumed there was no no burr after he polished the bolt face. But, I can imagine how a burr could do that.
 
#42
Does anyone know why my bolt face is making that quarter moon mark on my brass? It's new brass put into chamber to test only. No go and go gauge is good. Is this normal? Defiance anti x action
 

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