A friend of mine was having some problems with rounds getting stuck in his AR barrel and when ejecting the rounds the brass was tore up on the shoulder. After inspecting the barrel you can see gouge's in the barrel but he has no idea what may have caused it. He cut the barrel in half to get a better look at them. Any idea what may have caused this?
Deep gouge's in AR barrel
- Thread starter Raydee
- Start date
spat
.700 Nitro Express
A piece of something very hard stuck to a cartridge that then got embedded in the chamber wall when the round was fired.
Just a guess.
Just a guess.
GUNSICK
6.5 Creedmoor
Damage from improper use of cleaning rod in chamber? Who made the barrel?
Not sure, he is not a new shooter so I doubt he did it cleaning. According to him it was shooting fine and then all of the sudden when he pulled the trigger there was a click only. When he tried to eject the round it was stuck and required quite a bit of force to remove it. Once the round was out the next round was chambered and the same thing happened.
The upper is a PSA upper that he bought a couple years ago and has about 1k rounds through it. He does shoot reloads and cleans with stainless pins. Even if there was a couple pins in the case when it was shot they should have went down the barrel and not in the chamber where the damage is so I doubt that would be the culprit.
Any damage to the extractor? Possibly broke maybe with a losing battle with a stuck steel case.
meketrefe
.450/400 Nitro Ex
Judging for the tools marks the chamber was not the best (striations)
These could be put by the machine (like a broken reamer).
I have seen a number of PSA barrels with bad chambering jobs so I am not totally surprised because QA is non existent.
Same thing happens wiht other cheap kit barrels from OEM makers like model1.
These could be put by the machine (like a broken reamer).
I have seen a number of PSA barrels with bad chambering jobs so I am not totally surprised because QA is non existent.
Same thing happens wiht other cheap kit barrels from OEM makers like model1.
meketrefe
.450/400 Nitro Ex
A broken shell extractor should be softer than the barrel and should not butcher the chamber like that.
It has to be tool hardened steel.
The OP said this is a barrel that had at least 1k rounds shot through it. If it was a bad chamber, I would suspect it would have been difficult from day one. Use would have smoothed it if anything.
The defects appear to be over the striations in the chamber therefore occuring after the chamber was reamed out. I suspect a foreign object.
The defects appear to be over the striations in the chamber therefore occuring after the chamber was reamed out. I suspect a foreign object.
meketrefe
.450/400 Nitro Ex
It might depend on ammunition too specifically the bullet. While pointy bullets might catch others
with soft or wider noses might ride over.
Then the op should know. It has to be something very hard and with impact. hard to say with certainty but it is not a cleaning rod or broken shell extractor..
FirstRifle
.40 S&W
I think that I see three pitted areas in the shoulder area in the barrel.
Raydee, are those the "gouges" you describe?
Do the casings, which had the brass in the shoulder torn up, have evidence of expansion in the shoulder of the casing that corresponds with the pitting?
Raydee, are those the "gouges" you describe?
Do the casings, which had the brass in the shoulder torn up, have evidence of expansion in the shoulder of the casing that corresponds with the pitting?
If the pins were hard enough, it's possible they could have done this. Maybe he inserted a shell for a trial fit, not knowing that a few pins would drop out of the case and get hung up in the chamber. A few hits on the forward assist and you have the potential to make those marks. Look at the angle of the marks on the right side of the chamber. Those are not inline with the bore, as you would expect with small granular debris driven in by the shell. In addition, the angles on the right side would be challenging to accomplish with a longer tool. Stainless cleaning pins might be the right length for this.
Doing that to the chamber should have made some wicked damage to the brass in the process though. Maybe that brass was dismissed as a weak necked shell that collapsed, hence the reason it didn't fully chamber? The pins could have simply fallen out the bore during the shell removal.
Doing that to the chamber should have made some wicked damage to the brass in the process though. Maybe that brass was dismissed as a weak necked shell that collapsed, hence the reason it didn't fully chamber? The pins could have simply fallen out the bore during the shell removal.
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What I don't get about the pin theory is the would have had to gotten outside of a case to do that damage. If a pin is left in a case it most likely wouldn't be near the bullet end of the case due to the powder drop. So if the pin is somewhere in the powder mass than during the burn off there would be little chance for it exit the case. The only thing I can come up with it edited the case during extraction. Again I think this is a low probability of this happening. This doesn't mean any of this can't happen but I think the likelihood is low. My next part of the skepticism is if a pin on the courier of a case between the shoulder and a case would have enough force to gouge the steel. I would think a majority of the force would be absorbed by the brass.
Other than my disbelief of the pin theory I don't have a likely cause of those marks. It's a pretty neat discussion it sucks that we most likely never know what happened.
Other than my disbelief of the pin theory I don't have a likely cause of those marks. It's a pretty neat discussion it sucks that we most likely never know what happened.
I edited my post to say "inserted" rather than "loaded" a shell. Although just guesswork, my thought was that the pins fell out of a cleaned but otherwise unprocessed case that he test fit for some reason. I agree about the weaker brass absorbing most of the force, but if the assist was hit a few times I'm thinking the brass shoulder could have crumpled and become a more solid driving force on the pin. All the stars would have to be aligned just right for this to happen I suppose... if those stainless pins even have the hardness necessary to dig into the chamber steel if driven correctly.
meketrefe
.450/400 Nitro Ex
What pins do you mean?
meketrefe
.450/400 Nitro Ex
Oh. Stainless pins cannot do that. First you need to be able to close the camber to fire and you cant. Then the pins would have to be of some sharp hardened steel and they are not harder than the barrel. No way stainless pin can do that not even in an iron barrel from the middle ages let alone 416 or chromoly.
meketrefe
.450/400 Nitro Ex
Imo those look like they are not new scars. Look at the carbon inside them in contrast with the shining in the ridges.
I had some experience with this. Occasionally you have small cracks or holes in the case shoulder. Escaped jets of hot gas will etch a dimple in the chamber surface. This happens when brass was reloaded too many times or poor quality brass reloaded a few times. This is not all that uncommon. Many old barrels have them. I seen it many times with my Hawkeye bore scope. You can also see burn marks in the shoulders of fired cases that caused this. These dimples are harmless, unless they are so numerous as to deform the shape of the chamber. I don't think they played any negative role in this particular chamber.
PS. It's not the pins. Damage from fired pins looks different and occurs in the bore, not in the chamber.
PS. It's not the pins. Damage from fired pins looks different and occurs in the bore, not in the chamber.
Sharp edges on lugs in the barrel extension contribute to this. The holes/cracks will be in the same place, etching the same spot of the chamber. That's why the dimples are deeper then what occurs from a single crack.
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FirstRifle
.40 S&W
I agree with Mosinitis. If the reloaded casing had a weak spot or crack in the shoulder, that weak spot or crack could have ruptured during ignition, causing some hot gases to escape there, acting like a torch and burning the metal in the chamber. I wonder if subsequent casings might expand enough to have brass flow into the pitted areas, making the casings harder to extract. I'd check the brass that was hard to extract for marks on the shoulder.
Eddie Gunks
.338 Win Mag
Pretty extreme technique.
I agree with many times fired cases. I would not have cut a barrel in half in any case......well, if it was a 223 barrel with a 30 cal piece of lead in it i would have!
These scars look ugly, but they are not big enough to deform fired brass, at least not enough to cause a concern. Small holes and cracks in the shoulders of cases are more common in the AR brass, because during feeding they are slammed against sharp edges of lugs in the barrel extension. Some of the custom gunsmiths remove sharp edges from the barrel extension on quality match barrels, some don't.
Examine your fired brass in the shoulder and neck area and when you see a burn mark, it means there is a tiny hole or crack in there. Discard those cases, next time they are fired the hole will expend enough to etch the chamber wall. It has to be a burn mark, not just normal carbon fouling. It's easy to tell the difference between the two.
Corn cob will remove most of the carbon and let the burn marks stand out. Wet pins will probably remove all of the marks, so cases need to be examined before they are cleaned. Don't go crazy with it, even if you ignore these, the barrel will be shot out long before these etchings will cause any problems.
Now that Lyman came out with affordable digital bore scope, people will see lots of ugly things they were better off not seeing. I paid $750 for Hawkeye borescope years ago.
Even the quality match barrels that shot great looked ugly on the inside, so I stopped looking.
I know the extractor sits farther back but was curious if the extractor had splintered causing steel shavings to be pushed into the chamber.
No, I am 99% sure these were burned into the chamber.
Have to say this is an interesting thread.