5.56 AR reloading: Can Anyone ID what would cause these weird triangle shaped scrape marks/dents just below the shoulder?

WeR0206 · Dec 6, 2024

It doesn’t look like the same type of mark from too much lube during FL sizing. This actually has brass scraped off leaving an inverted triangle shape (most clearly seen in bottom row of bottom image).

Im going to toss this brass but was curious about root cause. My guess on the root cause is some debris in the chamber bc this mark was only on 10 out of my 50 pieces of brass

TheOfficeT-Rex · Dec 6, 2024

Got any marks on your brass deflector?

WeR0206 · Dec 6, 2024

TheOfficeT-Rex said:
Got any marks on your brass deflector?

hmm not really. My deflector usually leaves marks lower in the case and they are usually a thin flat line/dent not a scraped triangle shape which is what weirded me out.

reelserious · Dec 6, 2024

Looks like debris was in die when they were made. All identical marks. That would do it

99mpower · Dec 6, 2024

can you verify they were good before firing? or did it happen during firing… obviously alleviating a bunch of causes of you can narrow timeline

waveslayer · Dec 6, 2024

Possible reloading die, or the BCG when it's picking up a round

37L1 · Dec 6, 2024

Feed ramps or locking lugs

WeR0206 · Dec 6, 2024

99mpower said:
can you verify they were good before firing? or did it happen during firing… obviously alleviating a bunch of causes of you can narrow timeline

Not 100% sure but it very likely happened during firing. I feel like I would have noticed if they came out of the die like that.

Aftermath · Dec 6, 2024

If that happens during firing, you have a real mess in the chamber and I am surprised you can even load a round.

My guess is that is happening after firing and after extraction.

WeR0206 · Dec 6, 2024

Aftermath said:
If that happens during firing, you have a real mess in the chamber and I am surprised you can even load a round.

My guess is that is happening after firing and after extraction.

Agreed

99mpower · Dec 6, 2024

definitely after extraction

which only leaves ejection when it could happen..

Aftermath · Dec 6, 2024

99mpower said:
definitely after extraction

which only leaves ejection when it could happen..

Welp...thereyago

WeR0206 · Dec 6, 2024

99mpower said:
definitely after extraction

which only leaves ejection when it could happen..

How would it happen via ejection, when it hits the deflector?

Aftermath · Dec 6, 2024

Just film it and play it back in slomo

99mpower · Dec 7, 2024

WeR0206 said:
How would it happen via ejection, when it hits the deflector?

8 cycles to firing a weapon

feeding
chambering
locking
firing
unlocking
extraction
ejection
cocking

if it’s happening after brass comes out of chamber, only 2 options, during extraction or during ejection. not happening during cocking obviously

need to break it down, and find the simple process that’s causing it

LuckyLuke80 · Dec 7, 2024

Wild guess-maybe the bcg scraping/denting the next round down when picking up the round above it?

Rider47 · Dec 7, 2024

Try putting a small piece of 1/8" adhesive foam or rubber (Superglue!) on/over your deflector. This stopped dents for me. If this doesn't stop your dents, the problem is elsewhere.

WeR0206 · Dec 7, 2024

Rider47 said:
Put a small piece of 1/8" adhesive foam or rubber (Superglue!) on/over your deflector. This stopped dents for me.

I Will definitely do this especially since im usually shooting in the upper pressure range for 5.56

camocorvette · Dec 7, 2024

Put a piece of velcro fuzz on the brass deflector.

Your brass deflector is deflecting.

Aftermath · Dec 7, 2024

LuckyLuke80 said:
Wild guess-maybe the bcg scraping/denting the next round down when picking up the round above it?

I would think the round would be fireformed to the chamber upon ignition of the charge, removing any such little dent.

My money says during ejection. Film it using the slomo function on your phone and play it back. I bet you will see where it's hitting on the deflector triangle or near. At least it is consistent.

I don't think a brass catcher will do much to reduce that but you might try.

918v · Dec 7, 2024

reelserious said:
Looks like debris was in die when they were made. All identical marks. That would do it

No, if that were the case the dents would have been pushed out during firing. We’re talking about 60,000 PSI here.

camocorvette · Dec 7, 2024

Does the rifle chuck brass way to the rear like 5 o'clock?

reelserious · Dec 7, 2024

918v said:
No, if that were the case the dents would have been pushed out during firing. We’re talking about 60,000 PSI here.

Maybe shit in chamber then

Aftermath · Dec 7, 2024

reelserious said:
Maybe shit in chamber then

Truly doubtful.
Think about enough crud or a burr or whatever making a dent below the shoulder and how a round is chambered, then fired and extracted.
If there were something large enough to make that dent, I have serious doubt you could ever get a single round to chamber, let alone a dozen and definitely not from the spring action on the AR. I also doubt you would be able to extract a round fired with that sort of chamber issue.

BAMAboy18 · Dec 7, 2024

https://ar15brassdeflector.com/

LuckyLuke80 · Dec 7, 2024

Aftermath said:
I would think the round would be fireformed to the chamber upon ignition of the charge, removing any such little dent.

My money says during ejection. Film it using the slomo function on your phone and play it back. I bet you will see where it's hitting on the deflector triangle or near. At least it is consistent.

I don't think a brass catcher will do much to reduce that but you might try.

yeah, I see your point. Question for the OP-what changed to cause you to start seeing these dents? I have a hard time seeing the deflector all the sudden start denting the cases, but maybe so.

AZLong · Dec 7, 2024

The indent is below the shoulder. Not a lot of options here. Has to be after firing. Hit something on the way out, or the way down.

918v · Dec 7, 2024

I’m guessing it’s from the case hitting the barrel extension as it is being ejected.

Aftermath · Dec 7, 2024

918v said:
I’m guessing it’s from the case hitting the barrel extension as it is being ejected.

How?

Aftermath · Dec 7, 2024

camocorvette said:
Put a piece of velcro fuzz on the brass deflector.

View attachment 8563264

Your brass deflector is deflecting.

This really is the only option...the brass deflector is deflecting. Simple.

Simple solution right there, too.

AZLong · Dec 7, 2024

WeR0206 said:
It doesn’t look like the same type of mark from too much lube during FL sizing. This actually has brass scraped off leaving an inverted triangle shape (most clearly seen in bottom row of bottom image).

Im going to toss this brass but was curious about root cause. My guess on the root cause is some debris in the chamber bc this mark was only on 10 out of my 50 pieces of brass

View attachment 8562244

View attachment 8562245

One out of five...you shooting five rounds and closing the cover after each group?

Aftermath · Dec 7, 2024

AZLong said:
One out of five...you shooting five rounds and closing the cover after each group?

Would not the bolt open the dust cover when it cycles rearward before the round got there?

Deflector injury or something near the deflector.

918v · Dec 7, 2024

After thinking about it some more I think what is happening is the brass is bouncing back into the ejection port and is being hit by the bolt lugs as the bolt is pushing another round into the chamber.

Aftermath · Dec 7, 2024

918v said:
After thinking about it some more I think what is happening is the brass is bouncing back into the ejection port and is being hit by the bolt lugs as the bolt is pushing another round into the chamber.

How?

Aftermath · Dec 7, 2024

It seems that there are quite a few who have little to no understanding of:

1) How the AR cycles

2) Physics...even the simple type where you just imagine what is happening, no equations involved

WeR0206 · Dec 8, 2024

camocorvette said:
Does the rifle chuck brass way to the rear like 5 o'clock?

Cant tell bc I use a brass catcher but ill take it off next time

reelserious said:
Maybe shit in chamber then

I just inspected and cleaned the gun. Nothing in chamber.

LuckyLuke80 said:
yeah, I see your point. Question for the OP-what changed to cause you to start seeing these dents? I have a hard time seeing the deflector all the sudden start denting the cases, but maybe so.

One thing worth noting is that this was my first time shooting these higher pressure loads with AR-Comp and 8208XBR (near max 5.56). I didn’t see any pressure signs on the primers and no ejector burrs etc.. The triangle scrapping pattern on the brass is something ive never seen before but im with @Aftermath …after reading his well articulated posts it must be from the deflector.

99mpower · Dec 8, 2024

Aftermath said:
It seems that there are quite a few who have little to no understanding of:

1) How the AR cycles

2) Physics...even the simple type where you just imagine what is happening, no equations involved

not very many do.. its a cycle.. one step has to be done to start the next.. some steps just happen REALLY fast... haha

Oryx · Dec 8, 2024

What's the chance that it's hitting your brass catcher or that's not installed properly?

Doom · Dec 8, 2024

Dents like these usually have one source which is the load is too hot or the rifle is overpassed. Beyond the obvious the brass is probably not being ejected to the 3-4o'clock pattern. The brass is being flipped back hard into the deflector.

jzerfoss · Dec 8, 2024

You'll find lots of videos of slow motion ar15 ejection and find that cases hit on different areas of the brass deflector and different parts of the case itself. Your dents are more than likely from the cases hitting the bottom point of your brass deflector. I've had the same dents and changing the gassing would change the dent location or eliminate them.

918v · Dec 8, 2024

Aftermath said:
How?

36 seconds into the video

Aftermath · Dec 8, 2024

918v said:
36 seconds into the video

It would certainly be more informative if that little clip were shown from a greater distance. At what orientation is that rifle? Fingers of what appear to be a left hand at the end imply that it is upright and held normally but...that's merely an assumption. I would be willing to bet that particular malfunction is A) not very consistent {unlike the dents in the OP} and B) not caused by extra pressure or over gassing of the system.

Do notice, that casing that does actually re-enter the ejection port and creates a stoppage has far more and different damage than a little triangle of a dent below the case shoulder. If, in fact, the case were to be able to very consistently re-enter the ejection port and be hit by the forward moving bolt, there would most certainly be feeding and ejection issues to follow suit.

918v · Dec 8, 2024

I don’t know. I found this video because I remember watching another slomo where the cases were going back in and being bounced out by the bolt. It could be ammo related or a mechanical problem. But cases going back into the ejection port is possible. That’s all I was saying.

918v · Dec 8, 2024

WeR0206 said:
It doesn’t look like the same type of mark from too much lube during FL sizing. This actually has brass scraped off leaving an inverted triangle shape (most clearly seen in bottom row of bottom image).

Im going to toss this brass but was curious about root cause. My guess on the root cause is some debris in the chamber bc this mark was only on 10 out of my 50 pieces of brass

View attachment 8562244

View attachment 8562245

Can you show us the primers of these dented cases vs primers from cases that were not dented?

Also, it is ok to reuse them. The dents will pop out next time you fire them.

Aftermath · Dec 8, 2024

99mpower said:
not very many do.. its a cycle.. one step has to be done to start the next.. some steps just happen REALLY fast... haha

Just as a great deal of malfunctions in automatic handguns are caused by poor and/or weak grip and poor form, feeding and ejection issues with automatic rifles can be also be shooter related. Let an AR free-recoil and you will often find that it won't eject properly causing it to, in turn, not feed properly. Use low recoil ammo and you are going to have tuning issues...that system needs the full power to function properly. Use extra juiced rounds and the system needs to be tuned again. With AR's, I tend to play close to factory when I reload but have pretty much just stopped reloading for the AR. Not worth my time for the minimal gains over just buying ready to burn.

Let's not forget about feeding issues caused by magazines.

918v said:
I don’t know. I found this video because I remember watching another slomo where the cases were going back in and being bounced out by the bolt. It could be ammo related or a mechanical problem. But cases going back into the ejection port is possible. That’s all I was saying.

I get it.
Almost anything is possible once. That's Murphy's law, sorta.
I cannot fathom that happening with any sort of consistency without something intentional happening.

918v · Dec 8, 2024

Aftermath said:
Just as a great deal of malfunctions in automatic handguns are caused by poor and/or weak grip and poor form, feeding and ejection issues with automatic rifles can be also be shooter related. Let an AR free-recoil and you will often find that it won't eject properly causing it to, in turn, not feed properly. Use low recoil ammo and you are going to have tuning issues...that system needs the full power to function properly. Use extra juiced rounds and the system needs to be tuned again. With AR's, I tend to play close to factory when I reload but have pretty much just stopped reloading for the AR. Not worth my time for the minimal gains over just buying ready to burn.

Let's not forget about feeding issues caused by magazines.

I get it.
Almost anything is possible once. That's Murphy's law, sorta.
I cannot fathom that happening with any sort of consistency without something intentional happening.

The OP could be the cause, the ammo could be the cause. Some rounds could have been undercharged. That’s why I want to see the primers. It would also be nice if the OP could chrono the rounds to see if there is a relationship between the dented cases and lower velocity if some rounds are undercharged.

WeR0206 · Dec 8, 2024

Doom said:
Dents like these usually have one source which is the load is too hot or the rifle is overpassed. Beyond the obvious the brass is probably not being ejected to the 3-4o'clock pattern. The brass is being flipped back hard into the deflector.
View attachment 8563647

Thanks. Since I usually shooting pretty spicy 5.56 rounds Im going to switch from H2 to an H3 buffer (with super 42 spring)

jzerfoss said:
You'll find lots of videos of slow motion ar15 ejection and find that cases hit on different areas of the brass deflector and different parts of the case itself. Your dents are more than likely from the cases hitting the bottom point of your brass deflector. I've had the same dents and changing the gassing would change the dent location or eliminate them.

918v said:
Can you show us the primers of these dented cases vs primers from cases that were not dented?

Also, it is ok to reuse them. The dents will pop out next time you fire them.

Unfortunately I dumped the brass out of my case (lesson learned, next time I won’t do this) but I have attached a pic of the primers before I dumped the case. Going from left to right the first 5 columns are AR-Comp and the next 5 are 8208. Going front to back the grains of powder are going up by 0.2gr increments.

918v said:
The OP could be the cause, the ammo could be the cause. Some rounds could have been undercharged. That’s why I want to see the primers. It would also be nice if the OP could chrono the rounds to see if there is a relationship between the dented cases and lower velocity if some rounds are undercharged.

I don’t have a chrono but will be getting one sometime in the next 6 months or so. I mainly shoot for accuracy and monitor the brass for pressure signs as I go. Not sure how I missed these triangle marks but ill know to look for them next time.

I appreciate all the help/feedback!!

918v · Dec 8, 2024

U think maybe the dented brass came from the low end starting loads? Or the top end loads?

Bantam1 · Dec 9, 2024

It's hitting the barrel extension on the way out. This thing called the ejector is pushing the brass towards the ejection port side as the extractor is holding onto the rim while the bolt moves backwards. Sometimes the extension can be sharp on the ends of the lugs where the bolt locks into. Totally normal, just more obvious on some extensions depending on how sharp they are on the corners., how much extractor tension and ejector tension. Not a big deal really.

Close the bolt on an empty price of brass and cycle the bolt back by hand slowly. Watch the case clear the chamber and pull/pop over to the extension. There is the cause of the dents.

WeR0206 · Dec 9, 2024

Bantam1 said:
It's hitting the barrel extension on the way out. This thing called the ejector is pushing the brass towards the ejection port side as the extractor is holding onto the rim while the bolt moves backwards. Sometimes the extension can be sharp on the ends of the lugs where the bolt locks into. Totally normal, just more obvious on some extensions depending on how sharp they are on the corners., how much extractor tension and ejector tension. Not a big deal really.

Close the bolt on an empty price of brass and cycle the bolt back by hand slowly. Watch the case clear the chamber and pull/pop over to the extension. There is the cause of the dents.

I actually did something similar yesterday. I cleaned/lubed the chamber/bolt/bcg/etc. then put some loaded "dummy" ammo (with no primer/powder) I had on hand into a mag. Then I manually cycled the action to see if there was any scaping on the extension, etc. and the cartridges all came out smooth without any scraps or marks of any kind. This leads me to believe it's from the brass hitting the deflector with some spicy 5.56 loads. I guess it's possible there was some debris on the extension while some of the rounds were fired causing the marks as the brass was dragged but we'll see what happens next time I guess. Thanks for the input!

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5.56 AR reloading: Can Anyone ID what would cause these weird triangle shaped scrape marks/dents just below the shoulder?

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