Help identify odd marks on bolt

[Juggerxxx]

The rifle is a PSA-10 chambered in 6.5CM. Only 300-400 rounds on it and it has started double feeding. Meaning; not ejecting the spent case and picking up one from the magazine and then the issue of two hot dogs in one bun.
I started looking for what might be causing the issue and ran across these nasty deep marks on the bolt. Any idea what causes this and is it related to the double feed issue?

Background:
-I am not that fluent with ARs
-shooting hand loads of 147gr ELD with 41.9gr H4350 and starline brass
-only had double feeds a couple of time except this weekend. Shot about 50 rounds fine and the let the rifle sit for about an hour. Started shooting it again and double feeds started on every shot for the next 4 shots in a row.
-do have an adjustable gas block but haven’t messed with it since load development. Not even quite sure it was adjusted correctly but it seemed to cycle fine 99.9% of the time during load development.

 

[Rocketvapor]

Looks like some significant bolt bounce.

If it's only catching that small amount of the lugs when locked in, there is a problem about to happen.
I would look the bolt over for a crack starting near the cam pin or a shear starting in the cam pin itself.

 

[Juggerxxx]

Looks like some significant bolt bounce.

If it's only catching that small amount of the lugs when locked in, there is a problem about to happen.
I would look the bolt over for a crack starting near the cam pin or a shear starting in the cam pin itself.

I will look tomorrow for any cracks.
Any idea what causes bolt bounce? And how to fix it?
I have to assume the backside of the chamber lugs look the same?
I would also assume this issue would effect accuracy. Obviously a safety issue as well?

 

[Threadcutter308]

The rifle is a PSA-10 chambered in 6.5CM. Only 300-400 rounds on it and it has started double feeding. Meaning; not ejecting the spent case and picking up one from the magazine and then the issue of two hot dogs in one bun.
I started looking for what might be causing the issue and ran across these nasty deep marks on the bolt. Any idea what causes this and is it related to the double feed issue?

Background:
-I am not that fluent with ARs
-shooting hand loads of 147gr ELD with 41.9gr H4350 and starline brass
-only had double feeds a couple of time except this weekend. Shot about 50 rounds fine and the let the rifle sit for about an hour. Started shooting it again and double feeds started on every shot for the next 4 shots in a row.
-do have an adjustable gas block but haven’t messed with it since load development. Not even quite sure it was adjusted correctly but it seemed to cycle fine 99.9% of the time during load development. View attachment 7057671View attachment 7057672View attachment 7057673

I would contact PSA right away. I am not certain, but I seem to recall someone else here on the Hide having had similar problems within the past 6 months or so. It might be bad heat treating, but whatever it is, you are at risk of it failing. From what I recall, PSA jumped right on it and took care of it.

 

[Deleted member 113831]

The rifle is a PSA-10 chambered in 6.5CM. Only 300-400 rounds on it and it has started double feeding. Meaning; not ejecting the spent case and picking up one from the magazine and then the issue of two hot dogs in one bun.
I started looking for what might be causing the issue and ran across these nasty deep marks on the bolt. Any idea what causes this and is it related to the double feed issue?

Background:
-I am not that fluent with ARs
-shooting hand loads of 147gr ELD with 41.9gr H4350 and starline brass
-only had double feeds a couple of time except this weekend. Shot about 50 rounds fine and the let the rifle sit for about an hour. Started shooting it again and double feeds started on every shot for the next 4 shots in a row.
-do have an adjustable gas block but haven’t messed with it since load development. Not even quite sure it was adjusted correctly but it seemed to cycle fine 99.9% of the time during load development. View attachment 7057671View attachment 7057672View attachment 7057673

That fucked up edge is the lead edge when the bolt is locking up. It looks like the lugs are not fully engaging and the bolt isn't fully into battery. I would check that gun for a short headspace before I shot it again.

 

[Juggerxxx]

Thanks guys. I wanted to give them the benefit of the doubt and make sure I wasn’t doing something to cause the issue first but contacting them is on my list. I googled bolt bounce and got an idea of what exactly that is. Also saw some pictures of the same sort of damage associated with bolt bounce. I’ll do some more digging to see what causes it and possible solutions to rectify it.

It’s very odd it’s only on three of the lugs on that one side.

 

[ShooterwithNoName]

I agree with skookum, looks like the bolt has never actually fully locked closed. If you have access to a set of headspace, go/no-go gauges I would give them a try. Always good to have a set on hand for the calibers you run. Cheap insurance IMO...

 

[Rocketvapor]

You may be able to see how far the bolt rotates from underneath.
You can use the poor man's borescope to look at the extension lugs.
Mirror tape and a flashlight.

 

[oldfatguy]

Do not shoot it again until the problem has been fixed. There is a very real possibility of a catastrophic failure.

OFG

 

[RTH1800]

It’s getting ready to take an unscheduled trip. You are very lucky it has not done so.

 

[whatsupdoc]

I do not believe that the bolt is only engaging the barrel extension for .030 thousands (whatever) and holding.
That would mean that the bolt carrier is not going fully into battery.

I believe the bolt lugs are striking the edges of the barrel extension during extraction causing the cuts on the bolt lugs.
Possibly the bolt carrier cam slot not in spec, but something is out of spec.

 

[RTH1800]

Those lugs are cut deeply. If only engaging that much it should not fire.

 

[Rocketvapor]

Not extracting all of a sudden? What do the cases look like.
Sticking cases, extractor coming over the rim could cause the bolt to skip a little.
Go from full rotation, bolt loads up on the case, skips over some of the extension lug, lands near the edge.
Picture of a case rim that did not extract and a pic of the cam pin.

Push the bolt into the carrier and rotate back and forth. Anything more than a few degrees movement is too much.

When a case comes out normally the unlocking ramp (unlock curve of the cam pin slot) will pull and rotate the bolt off the lugs smoothly maybe wearing the edges a little. Hard extraction will cause the bolt to stay on the rim then snap over causing waves in the wear surface. I imagine a severe case could cause jumps and skips hitting on the edge of the lug.
Only striking lugs on one side says something is not aligned or has yielded or come loose. Lugs don't look worn, just damaged. Loose barrel nut?

 

[Juggerxxx]

Not extracting all of a sudden? What do the cases look like.
Sticking cases, extractor coming over the rim could cause the bolt to skip a little.
Go from full rotation, bolt loads up on the case, skips over some of the extension lug, lands near the edge.
Picture of a case rim that did not extract and a pic of the cam pin.

Push the bolt into the carrier and rotate back and forth. Anything more than a few degrees movement is too much.

When a case comes out normally the unlocking ramp (unlock curve of the cam pin slot) will pull and rotate the bolt off the lugs smoothly maybe wearing the edges a little. Hard extraction will cause the bolt to stay on the rim then snap over causing waves in the wear surface. I imagine a severe case could cause jumps and skips hitting on the edge of the lug.
Only striking lugs on one side says something is not aligned or has yielded or come loose. Lugs don't look worn, just damaged. Loose barrel nut?

All great info guys thank you!
I do have a bore scope so I will break it out and take a look at the backside of the lugs.
Here is the cam pin and brass. The one with the dented shoulder was a live round that got damaged from one of spent rounds.

 

[Juggerxxx]

Push the bolt into the carrier and rotate back and forth. Anything more than a few degrees movement is too much.

When the bolt is pushed into the carrier it is impossible for my to gauge degrees of angle. I get what you are saying but I have to equate it to inches of slop and it feels like a very minimal amount as in 0.005” from left all the way to right.

 

[Rocketvapor]

Another 'Guess' is short stroking.
Bolt going back in and not rotating fully catching only the edge.
Manual removal causing some damage to the bolt lugs.
But I would not imagine as severe as yours.
And, what caused case necks to bend outwards?

It would be nice to add the solution, just for the knowledge, but when PSA fixes it, we might not ever know

 

[2aBaC̶a̶]

Those marks and your failure to eject issues may not be related.

Do you have dummy rounds? Do they cycle with bolt fully into battery?

Can you post pics of the bolt face and primer end of spent cases?

 

[Juggerxxx]

Another 'Guess' is short stroking.
Bolt going back in and not rotating fully catching only the edge.
Manual removal causing some damage to the bolt lugs.
But I would not imagine as severe as yours.
And, what caused case necks to bend outwards?

It would be nice to add the solution, just for the knowledge, but when PSA fixes it, we might not ever know

I was thinking the same thing. I will do my best to get an answer.

 

[Juggerxxx]

Those marks and your failure to eject issues may not be related.

Do you have dummy rounds? Do they cycle with bolt fully into battery?

Can you post pics of the bolt face and primer end of spent cases?

I don’t have any dummy rounds but all loaded rounds I have ever chambered always eject just fine. Of coarse manually and not following a fired round.

Here is the bolt face and primers of the damaged rounds. They do have some nasty ejector marks but those still appear on rounds that are 2 full grains lower.
It does appear the bolt face is being cut into at the same diameter of the primers. But I don’t see much creatoring or flattening of the primers?

 

[Rocketvapor]

Put your BCG back together, into the receiver, look from the bottom and see that the bolt lugs fully engage.
Try again with a sized case.

Clean off the bolt face to see if that looks like gas cutting.
Not related to your problem.

 

[2aBaC̶a̶]

If it short strokes how does it pick up another round and double feed?

This does look like it's short stroking and crashing the spent case into the chamber or feed ramps. But not enough to eject? Or is the extractor not ejecting? Have you checked the adjustable gas block screws?

Is the bolt in backwards? I've done that.

Dual extractors... are they both working? Disassemble and check internals?

 

[Rocketvapor]

I hate to say it but unless someone comes up with a good answer, it's probably going back and PSA won't let you know what THEY did wrong

 

[Juggerxxx]

If it short strokes how does it pick up another round and double feed?

This does look like it's short stroking and crashing the spent case into the chamber or feed ramps. But not enough to eject? Or is the extractor not ejecting? Have you checked the adjustable gas block screws?

Is the bolt in backwards? I've done that.

Dual extractors... are they both working? Disassemble and check internals?

I did check the ejectors and they are very functional. Not rough or sticky and have a good amount of spring force. I almost always put the bolt in backwards but it’s impossible to install the cam pin due to a smaller cam pin hole in the bottom of the bolt.

 

[Juggerxxx]

I hate to say it but unless someone comes up with a good answer, it's probably going back and PSA won't let you know what THEY did wrong

I hate to say it but unless someone comes up with a good answer, it's probably going back and PSA won't let you know what THEY did wrong

I agree but I will try to get an answer. It’s very unfortunate because I was very happy with rifle otherwise. It had been very accurate during load development for both the 140gr and 147gr ELDs. I have another PSA AR15 223 with an 8.5” barrel and it has ran flawless so far for ~500 rounds. Eats all types of ammo without a single issue. The 8.5” barrel was the one I was worried about.

 

[Rocketvapor]

The thing that gets me is the 3 lugs on one side getting dinged but not the others.
They are centered around one ejector but probably just a coincidence.
If everything is in alignment barrel/ upper, extension/ chamber, how can 3 lugs hit and not the others.
The fact that it ran fine for a while then started this seems to indicate something changed.
The rounds that got stuck did fire so they went into battery.
It's extraction/ejection that seems to be the issue.

Things that can change?
Gas block loose and moved,
Barrel nut loose,
A piece of brass in the chamber/leade,
Gas key loose, damaged?
Something changed, failed, almost failed, got worse.
How's the extension lugs look?
Let us know what PSA says, this is interesting.

Order a spare bolt when you get it back. Blend that edge where the extractor hits the brass before it snaps over the rim going in.
That's a source of brass on the bolt face. Brass color is OK, brass flakes are not.

One last (? ) question;
When the next round jammed up was the bolt behind it or could it have popped up out of the mag?

 

[Juggerxxx]

The thing that gets me is the 3 lugs on one side getting dinged but not the others.
They are centered around one ejector but probably just a coincidence.
If everything is in alignment barrel/ upper, extension/ chamber, how can 3 lugs hit and not the others.
The fact that it ran fine for a while then started this seems to indicate something changed.
The rounds that got stuck did fire so they went into battery.
It's extraction/ejection that seems to be the issue.

Things that can change?
Gas block loose and moved,
Barrel nut loose,
A piece of brass in the chamber/leade,
Gas key loose, damaged?
Something changed, failed, almost failed, got worse.
How's the extension lugs look?
Let us know what PSA says, this is interesting.

Order a spare bolt when you get it back. Blend that edge where the extractor hits the brass before it snaps over the rim going in.
That's a source of brass on the bolt face. Brass color is OK, brass flakes are not.

One last (? ) question;
When the next round jammed up was the bolt behind it or could it have popped up out of the mag?

Very good list of items.
I took this photo from someone else that had posted a similar issue with ejecting. They did not mention anything about damaged lugs but I have asked them to inspect theirs for damage and also if they resolved the ejecting issue or not.
My ejection issue looks exactly like the photo below they experienced.

 

[Rocketvapor]

Looks like lug damage in the pic.
Did a little reading and some bolts have a bevel in that area that might get dinged a little.
Yours looks square (on the good ones).
Here's the bevel. This is a 800 round 22 Nosler bolt.
About 600 on this bolt.
Big difference as this is a NO-GAS AR-15 manual side pull.
But it does show the bevel applied when new.
Second pic is what I did to reduce brass flakes

 

[Juggerxxx]

Holy shit your right!!!!!! I didn’t even notice the damage in the photo. One of the same exact lugs to!!!!!

 

[2aBaC̶a̶]

I would disassemble the bolt and inspect all the parts, specifically extractor. Maybe make the mods suggested above.

My guess is either an ejector problem or that your gas system changed just enough to allow the bolt to barely pick up a new round but not far enough for the spent case to eject.

You can put together some dummy rounds pretty easy if you reload. Even leave in the spent primer. Cycle a bunch of times by hand to see if you can repeat it. It may just happen with the shock of live fire.

 

[Juggerxxx]

Well I received the complete upper back from PSA yesterday. It looked as if nothing was changed on it and the marks were still on the bolt. I called them up and they said the wear on the bolt is “normal” and all they did was change an ejector o-ring and tune the gas block. They also said they fired ~30 rounds of various ammo and it did not exhibit any issues.
I guess I will test it out at the range cautiously and see what the results are.

 

[bfoosh006]

Does your PSA have an Adj. GB ?

Your "double feed" is classic over gassed cyclic speed to me.

The fired case is not getting enough "time to eject" prior to the next case being feed... IE the cyclic speed is "over whelming" the ejector springs ability to eject the case.

Also the comment about the outside pointed edges of the extractor or spot on. If the "outside pointed edges" are to pointy, the extractor will grip the ejecting case longer then wanted... in other words it can not readily flip out and roll away from the extractor claw.

From the internet...

The two outside ones have the rounded "ends" on the claw

 

[bigjake83]

Well I received the complete upper back from PSA yesterday. It looked as if nothing was changed on it and the marks were still on the bolt. I called them up and they said the wear on the bolt is “normal” and all they did was change an ejector o-ring and tune the gas block. They also said they fired ~30 rounds of various ammo and it did not exhibit any issues.
I guess I will test it out at the range cautiously and see what the results are.

I would definitely investigate that some more, and ask for pictures of a new Bolt and what it looks like.

Unless those notches are carved in there from the factory that is not acceptable and I would not shoot it anymore until talking to somebody else at PSA. They could have at least replace the bolt anyway because the coating is flaking off as it is.

 

[2aBaC̶a̶]

You probably won't see any modification they made. It could have been as simple as the little rubber O-ring in the extractor.

Go shoot it using a couple of different boxes of factory ammo.

 

[Juggerxxx]

Took the upper to the range that PSA shipped back. It ran flawless for 50 rounds so we shall see how the next 500 go. Keeping my fingers crossed.
I am also posting a before and after comparison for when I True and Glue my receiver. I will post it in the general gas gun thread.

 

[bfoosh006]

Did we ever completely figure out what was causing the peening marks on the bolt lugs ?

While not just a PSA Large Frame issue, I have seen other random cases of this "bolt lug peening" ... 5.56 bolts, 7.62x39 bolts, Large frames.. etc...

Is this a over gassed / too violent cyclic speed thing, or a carrier group / cam pin timing issue ?

 

[bfoosh006]

As for the groups... were they fired in any specific order ? Left to right ?

Center first, then left, then right ?

I ask because if there was a barrel "seasoning" effect going on.

 

[Juggerxxx]

Did we ever completely figure out what was causing the peening marks on the bolt lugs ?

While not just a PSA Large Frame issue, I have seen other random cases of this "bolt lug peening" ... 5.56 bolts, 7.62x39 bolts, Large frames.. etc...

Is this a over gassed / too violent cyclic speed thing, or a carrier group / cam pin timing issue ?

No clue on what caused the marks. PSA said that wear was normal. Lol

 

[Juggerxxx]

As for the groups... were they fired in any specific order ? Left to right ?

Center first, then left, then right ?

I ask because if there was a barrel "seasoning" effect going on.

Started from top left and worked to the right and then down from left to right. I have noticed a trend that this gun groups better or at least more consistent when it’s hot. The groups when zeroing in before shooting the target above was ugly. I have to check my log book but I believe I am up to ~400 rounds without a barrel cleaning. It’s possible but I don’t think PSA cleaned the barrel.

 

[bfoosh006]

No clue on what caused the marks. PSA said that wear was normal. Lol

Humph.... none of mine show marks like that.

I will say, I run heavy buffer weights ( 9.3oz rifle, 5.4oz carbine ) , Tubbs Flatwire 308 recoil spring ( in both rifle and carbine ) and SLR Adj. GB's... to slow down the cyclic speed.

Its almost like your bolt is being forced open at that specific moment / bolt cam position....

Remind me what recoil assm. specifics... 3.25" buffer.... 2.5" Buffer ? What recoil spring, factory ? No marks on the lower receiver at the buffer tube threads ?

Seriously sounds over gassed / and you need a slower cyclic speed ( not that anyone would ever notice it the real world, except from the lessened preceived recoil impulse )

And leaving the bolt locked just a about 1.5 milliseconds longer ( no sh_t , a well respected AR writer measured it ) should help a lot of the double feeds... by slowing everything down slightly... and allowing extraction at a lower chamber pressure. Just like those popular +2 gas lengths.

 

[Juggerxxx]

Ok well another 40-50 rounds fired from the PSA today without a single issue. My hope for just adjusting the gas setting went up a bit more. I just wish I knew if they adjusted it more or less since I messed with the setting a good amount.