Not a reload... but needs some expertise

[Doug k 042414]

Hey all. As the title states, I had a catastrophic failure on my bolt gun that was not from a reload. However, I am a reloader and need some consensus on the root cause. Is this from an over loaded “factory” round, bad metallurgy, or a combo of both? Pics listed below.

Specs
26” criterion
Action-I won’t name yet to save them any infamy
Chassis- MDT LSS-XL gen 2

I have sent a message to the ammo manufacturer in hopes that they do the right thing and recoup me for my loss. My action has a replaceable bolt head and I’m really pressed for time and cash before an upcoming comp.

I believe the issue to be an extremely over charged round. Tell me what you think...

 

[myronman3]

the only thing i have to say on it is....

so much for the arguement “factory ammo being safer than handloads”. my brother had factory ammo overcharge bust up a rifle on him. and with all the handloading i’ve done, i’ve never had an issue....and i shoot more than my brother...or i used to, pre-covid anyways.

 

[6.5SH]

Given the good radius on the primer looks more like a chambering issue IMO.

 

[Vasily]

Factory or custom chambering? Round count?

 

[Vasily]

Majority of time this is caused by excessive headspace. A smith can check relatively easy for you. This will also give you some credibility with the ammo company if the issue is not headspace.

 

[supercorndogs]

Overload would blow the primer out. Looks a lot like what i would suspect would happen were you to shoot a 6GT in 6mm Creedmore chamber or something like that. I.E too much headspace. I don't see any reason to think the ammo was at fault.

 

[BullGear]

Are you sure you don't have a plugged barrel?

 

[Vasily]

Are you sure you don't have a plugged barrel?

This for sure, best not forget the cleaning rod

 

[Milo 2.5]

Wow.

 

[ShtrRdy]

I'm gonna guess a headspace issue.

 

[m1match]

The primer doesn't look overpressure, but excessive headspace would have caused a case head separation and gas venting but it wouldn't have sheared the lugs off the bolt head would it? The sheared lugs look like way excessive overpressure doesn't it?

Normally dangerously overpressure rounds will blow the case head which you don't have, however your case head does look like it had ejector swipe and indentation in the case head, so perhaps it was overpressure.

Was this a brand new action? If it was I might speculate that you had a bad bolt head that failed at normal pressures.

So it could caused by overpressure ammo, excessive headspace, or a bad bolt head, which could involve the ammo manufacturer, the gunsmith who built and chambered the rifle, or the action manufacturer.

I think I just raised more questions instead of providing answers, but as I was thinking things through while typing, I realized your situation is not simple to diagnose.

 

[TheOfficeT-Rex]

There are some 'pressure signs,' but I would expect to see those if the case took a running start at the bolt head. But too excessive, and I'd expect that you would have had some light strikes in the past unless the firing pin protrusion was on the longer side...

Are you sure it's the ammo? Have you fired other ammo in this barrel?
If it's a new gun, I'd involve the manufacturer too. If it's a new barrel, the gunsmith is getting the same email. Then they can fight over who's getting the pieces sent to them.

Also, might want to police up those pictures if you really didn't want to name and shame....

 

[Yondering]

There are some 'pressure signs,' but I would expect to see those if the case took a running start at the bolt head. But too excessive, and I'd expect that you would have had some light strikes in the past unless the firing pin protrusion was on the longer side...

Are you sure it's the ammo? Have you fired other ammo in this barrel?
If it's a new gun, I'd involve the manufacturer too. If it's a new barrel, the gunsmith is getting the same email. Then they can fight over who's getting the pieces sent to them.

Also, might want to police up those pictures if you really didn't want to name and shame....

Those are classic "false pressure signs" that are really signs of excess headspace.

 

[Doug k 042414]

The rifle was at round 82 of 83 for the day.
Total round count: 500
After firing the last round, the bolt had what started to feel like a heavy bolt lift. But would not unlock. After a minute or two of working the bolt back and forth, the lugs sheered off and came free.

With regards to the ammo, the seating depth was all over the place. I observed around 40-thou of variance. This meant that some were jamming when fed. I pulled these out and deconstructed them. The rest were were shot to fire form the brass.

So I guess for educational purposes and not to stir the pot, if 298 out of 500 rounds (the rest have either not been shot of were deconstructed due to jamming into the lands) fired fine, then I’m not understanding how this is an excessive hs issue. I have also put 200 hand loads through this with no issue and minimal resizing. Again, not trying to Piss in anyone’s wheaties... just looking for knowledge.

The barrel is a prefit. I used Manson headspace gauges to set head space.

 

[Longshot284]

@Ledzep what are your thoughts on this?

 

[Milo 2.5]

The rifle was at round 82 of 83 for the day.
Total round count: 500
After firing the last round, the bolt had what started to feel like a heavy bolt lift. But would not unlock. After a minute or two of working the bolt back and forth, the lugs sheered off and came free.

With regards to the ammo, the seating depth was all over the place. I observed around 40-thou of variance. This meant that some were jamming when fed. I pulled these out and deconstructed them. The rest were were shot to fire form the brass.

So I guess for educational purposes and not to stir the pot, if 298 out of 500 rounds (the rest have either not been shot of were deconstructed due to jamming into the lands) fired fine, then I’m not understanding how this is an excessive hs issue. I have also put 200 hand loads through this with no issue and minimal resizing. Again, not trying to Piss in anyone’s wheaties... just looking for knowledge.

The barrel is a prefit. I used Manson headspace gauges to set head space.

First, what is deconstructed? Pulling the bullet?
I think your bolt head was weak. I have always been under the assumption bolts were heat treated to be harder than the action itself.
I have never seen a shoulder blown off a case. I have seen cases come apart on the first firing, always closer to the case head. Not saying it is not headspace, this is just weird. is the barrel still tight? If it is headspace, the bill is on you.

I would take a caliper to the fired brass from this batch of ammo and see if a story can be told. How much case growth in key spots.

 

[Milo 2.5]

Overload would blow the primer out. Looks a lot like what i would suspect would happen were you to shoot a 6GT in 6mm Creedmore chamber or something like that. I.E too much headspace. I don't see any reason to think the ammo was at fault.

I have managed to do what you mentioned, 6x47 in a 6 comp match chamber. I managed to get 2 off.

 

[supercorndogs]

The rifle was at round 82 of 83 for the day.
Total round count: 500
After firing the last round, the bolt had what started to feel like a heavy bolt lift. But would not unlock. After a minute or two of working the bolt back and forth, the lugs sheered off and came free.

With regards to the ammo, the seating depth was all over the place. I observed around 40-thou of variance. This meant that some were jamming when fed. I pulled these out and deconstructed them. The rest were were shot to fire form the brass.

So I guess for educational purposes and not to stir the pot, if 298 out of 500 rounds (the rest have either not been shot of were deconstructed due to jamming into the lands) fired fine, then I’m not understanding how this is an excessive hs issue. I have also put 200 hand loads through this with no issue and minimal resizing. Again, not trying to Piss in anyone’s wheaties... just looking for knowledge.

The barrel is a prefit. I used Manson headspace gauges to set head space.

If you made 70k, 80k, or 90KPSI. The case head would look like belted mag and the primer hole would look like extra large LRP.

There is nothing to obstruct your bolt lugs from opening in there. I would guess they broke during the process of firing the round and not during the process of removing the round. The bolt lugs breaking could cause everything you see there.

 

[Doug k 042414]

First, what is deconstructed? Pulling the bullet?
I think your bolt head was weak. I have always been under the assumption bolts were heat treated to be harder than the action itself.
I have never seen a shoulder blown off a case. I have seen cases come apart on the first firing, always closer to the case head. Not saying it is not headspace, this is just weird. is the barrel still tight? If it is headspace, the bill is on you.

I would take a caliper to the fired brass from this batch of ammo and see if a story can be told. How much case growth in key spots.

The primer doesn't look overpressure, but excessive headspace would have caused a case head separation and gas venting but it wouldn't have sheared the lugs off the bolt head would it? The sheared lugs look like way excessive overpressure doesn't it?

Normally dangerously overpressure rounds will blow the case head which you don't have, however your case head does look like it had ejector swipe and indentation in the case head, so perhaps it was overpressure.

Was this a brand new action? If it was I might speculate that you had a bad bolt head that failed at normal pressures.

So it could caused by overpressure ammo, excessive headspace, or a bad bolt head, which could involve the ammo manufacturer, the gunsmith who built and chambered the rifle, or the action manufacturer.

I think I just raised more questions instead of providing answers, but as I was thinking things through while typing, I realized your situation is not simple to diagnose.

I’ll try and answer both simultaneously.
1 out of every 15-20 rounds showed light ejector swipe. That was with virgin brass loaded by the ammo company. Once fire formed, the brass was bumped 2 thou and I ran load development. This was not one of my reloads as stated above.

The pics below show the growth from virgin to fire formed. By my understanding (and again not being a smart ass) there was 8thou of growth from start to finish. The barrel was still set to 50 ft lbs when I disassembled it. When I set head space, it was over by two thou on the NG, but started to mar the barrel. That was with the cocking MEC out and ejector removed (manson’s do not need the ejector removed.

De constructed is just what you asked- pulled pulled and powder dumped.

I guess my overall question (as I’m great full for your guys’ expertise on this) is do you really think 2 thou too long is too much?

 

[Doug k 042414]

First, what is deconstructed? Pulling the bullet?
I think your bolt head was weak. I have always been under the assumption bolts were heat treated to be harder than the action itself.
I have never seen a shoulder blown off a case. I have seen cases come apart on the first firing, always closer to the case head. Not saying it is not headspace, this is just weird. is the barrel still tight? If it is headspace, the bill is on you.

I would take a caliper to the fired brass from this batch of ammo and see if a story can be told. How much case growth in key spots.

I’ll run a size comparison and post the sizes momentarily

 

[Milo 2.5]

If your pics are a new to fired, yes .008" growth is excessive, and I am no expert, but I say not enough to blow a shoulder off.

I can't wait till you get this nailed down, it will be interesting for sure.
Edit: Also, case growth with a different brand of brass may be less or more, so headspace here could be subjective.

 

[Doug k 042414]

My thought too, but I’m no expert. As I stated before, this was round 299 of 300 I was fire forming for reloading purposes. The bullet, powder, primer combo itself did not preform at all out of my barrel. I attached what I refuse to call groups (@100 yds) for pic 1. Pic 2 is from a lighter bullet that has been substantially better with absolutely no pressure signs.

Like I said (and I appreciate whoever stated that I should police up the first batch of photos, I’m not trying to burn anyone, but I did notify the ammo company of the inconsistencies I found in their ammo and that that they might need to be on the look out for more if this were a pressure issue.

Again, no expert here, that’s why I’m asking

 

[308pirate]

I think your bolt head was weak. I have always been under the assumption bolts were heat treated to be harder than the action itself.

I would not automatically make that assumption

Also hardness isn't the only material property that matters in rifle (or any pressure vessel for that matter) design.

There's much more to this topic and it isn't one for layman's speculation.

 

[Milo 2.5]

My thought too, but I’m no expert. As I stated before, this was round 299 of 300 I was fire forming for reloading purposes. The bullet, powder, primer combo itself did not preform at all out of my barrel. I attached what I refuse to call groups (@100 yds) for pic 1. Pic 2 is from a lighter bullet that has been substantially better with absolutely no pressure signs.

Like I said (and I appreciate whoever stated that I should police up the first batch of photos, I’m not trying to burn anyone, but I did notify the ammo company of the inconsistencies I found in their ammo and that that they might need to be on the look out for more if this were a pressure issue.

Again, no expert here, that’s why I’m asking

Your bolt head came apart, more pressure and you could have been sucking on the bolt. That should not be normal. No matter what you do here, I would look into that, maybe a hardness test, or find someone who could tell you if it was fractured beforehand.

 

[308pirate]

Majority of time this is caused by excessive headspace. A smith can check relatively easy for you.

The bolt's missing all of its lugs. The headspace datum is gone.

How is anyone going to check headspace after the fact?

 

[308pirate]

Your bolt head came apart, more pressure and you could have been sucking on the bolt. That should not be normal. No matter what you do here, I would look into that, maybe a hardness test, or find someone who could tell you if it was fractured beforehand.

The only people who can tell whether the bolt is right or wrong is whoever manufactured it.

Sending it to a lab will tell you a lot about it. What it won't tell you is if the bolt is manufactured to print specifications, including its material properties.

Why? Because only the manufacturer knows what those specs are supposed to be.

 

[supercorndogs]

The bolt's missing all of its lugs. The headspace datum is gone.

How is anyone going to check headspace after the fact?

Put a new bolt head on.

 

[308pirate]

Put a new bolt head on.

It's no longer the bolt that blew up then. Whatever you learn from that would be pure speculation and anyone with two brain cells to rub together will discredit any conclusion stemming from doing that.

 

[Milo 2.5]

The only people who can tell whether the bolt is right or wrong is whoever manufactured it.

Sending it to a lab will tell you a lot about it. What it won't tell you is if the bolt is manufactured to print specifications, including its material properties.

Why? Because only the manufacturer knows what those specs are supposed to be.

I agree with you here, but how many times have we heard about warranty being skirted because of outside circumstances, keep the honest, honest.

 

[supercorndogs]

It's no longer the bolt that blew up then. Whatever you learn from that would be pure speculation and anyone with two brain cells to rub together will discredit any conclusion stemming from doing that.

Do you know why they can make prefits and different bolt heads for custom actions?

 

[whatsupdoc]

If your pics are a new to fired, yes .008" growth is excessive, and I am no expert, but I say not enough to blow a shoulder off.

I can't wait till you get this nailed down, it will be interesting for sure.
Edit: Also, case growth with a different brand of brass may be less or more, so headspace here could be subjective.

Typically SAAMI chamber datum tolerance is .010 Min to Max add the case tolerance to that so .008 growth
is not excessive.

 

[Milo 2.5]

It's no longer the bolt that blew up then. Whatever you learn from that would be pure speculation and anyone with two brain cells to rub together will discredit any conclusion stemming from doing that.

I bought a Bighorn TL3, chambered it up, back then bolt heads were coated with some BS substance. I complained, they sent a new bolt head, claim to fame was tolerances, plug and play.

 

[Dthomas3523]

Do you know why they can make prefits and different bolt heads for custom actions?

What he’s saying is that you’ll never know if that particular bolt head was out of spec.

 

[supercorndogs]

I am saying that is how you would check the headspace.

 

[TheOfficeT-Rex]

Those are classic "false pressure signs" that are really signs of excess headspace.

I agree with you, I just haven't figured out the new sarcasm font yet.

The rifle was at round 82 of 83 for the day.
Total round count: 500
After firing the last round, the bolt had what started to feel like a heavy bolt lift. But would not unlock. After a minute or two of working the bolt back and forth, the lugs sheered off and came free.

With regards to the ammo, the seating depth was all over the place. I observed around 40-thou of variance. This meant that some were jamming when fed. I pulled these out and deconstructed them. The rest were were shot to fire form the brass.

So I guess for educational purposes and not to stir the pot, if 298 out of 500 rounds (the rest have either not been shot of were deconstructed due to jamming into the lands) fired fine, then I’m not understanding how this is an excessive hs issue. I have also put 200 hand loads through this with no issue and minimal resizing. Again, not trying to Piss in anyone’s wheaties... just looking for knowledge.

The barrel is a prefit. I used Manson headspace gauges to set head space.

Even with the ammo discrepancies, because of the low round count I think the bolt and action need to go back to the manufacturer. They should be able to check the bolt as well as your prefit job, as I'm assuming it's done with a barrel nut system - they should be able to check if the barrel walked out on you at all when they inspect it.

ETA: If you have a micrometer, it may be worth measuring case diameter of a few cases near the head, to check for overpressure via expansion.

You blew a case and sheared bolt lugs, but without getting hands on I doubt we're going to be able to tell which happened first.

 

[Doug k 042414]

This action company makes “tool-less interchangeable bolt heads. They make interchangeable heads. The bolt resembles a Schultz and Larsen pattern so changing isn’t the issue, but I was asking and putting possibly myself and the incident out there for the good of future shooters whether it’s my fault or not. If it is, I accept that fully.

I also don’t want this Wonkie shit to happen again when I get said new bolt head.

Thanks for all the posts this far. I have come to most of the same potential culprits as well, myself included.

Do you know why they can make prefits and different bolt heads for custom actions?

 

[THEIS]

Hi,

So it is a 6GT and "factory" ammunition.

Which is really not "factory" ammunition; more like guy sitting at his reloading bench with IF your are lucky slightly more commercialized equipment that what everyone has at their house.

Not hard to make errors IF there is not massive oversight and operating procedures/protocols.

Now onto the bolt---
ONLY the manufacturer has the alloy spec sheets with the alloy certification sheets to compare that broken bolt to.
ONLY the manufacturer has the heat treatment spec sheets with the heat treatment certification range to compare that broken bolt to.

IMO I just cannot see enough pressure being from that 6GT case to break those lugs in itself without just a "perfect storm" of events.

1. Excessive headspace..(Did the extractor click over the base before firing?)
2. Have you pulled bullets from ammunition in same box to check powder? Not only weight but actual powder itself?
3. Bad batch of alloy or heat treatment process gone wrong.


Edited To Add:
Wait, What...I am confused. Were you shooting "factory" ammo or were you on round 299 fireforming?

Sincerely,
Theis

 

[supercorndogs]

I am not sure what you would have done to cause this in 300rds. I would be suspect of the bolt as Milo suggested. And as 308P suggested the best way to find out, is going to be to send the bolt head to the manufacture.

 

[Doug k 042414]

I agree with you, I just haven't figured out the new sarcasm font yet.
I agree. Unfortunately, I had to pull the barrel to get the ligs out of the locking recess. They were seized and the casing was stuck in place from a piece of the left lug. So I was in able to check anything except for the barrel nut torque which was still at 50 ft lbs if the torque spect on the wrench are relatively correct


Even with the ammo discrepancies, because of the low round count I think the bolt and action need to go back to the manufacturer. They should be able to check the bolt as well as your prefit job, as I'm assuming it's done with a barrel nut system - they should be able to check if the barrel walked out on you at all when they inspect it.

ETA: If you have a micrometer, it may be worth measuring case diameter of a few cases near the head, to check for overpressure via expansion.

You blew a case and sheared bolt lugs, but without getting hands on I doubt we're going to be able to tell which happened first.

 

[Doug k 042414]

Thanks THEIS.
I did pull some powder and weigh and check. It’s ball type powder which makes me think that is might be Staball oranother close to it. I’ll have to check the average pour weight that I weights from the rounds that I tore apart. I’ll see what I can find and post soon.

Hi,

So it is a 6GT and "factory" ammunition.

Which is really not "factory" ammunition; more like guy sitting at his reloading bench with IF your are lucky slightly more commercialized equipment that what everyone has at their house.

Not hard to make errors IF there is not massive oversight and operating procedures/protocols.

Now onto the bolt---
ONLY the manufacturer has the alloy spec sheets with the alloy certification sheets to compare that broken bolt to.
ONLY the manufacturer has the heat treatment spec sheets with the heat treatment certification range to compare that broken bolt to.

IMO I just cannot see enough pressure being from that 6GT case to break those lugs in itself without just a "perfect storm" of events.

1. Excessive headspace..(Did the extractor click over the base before firing?)
2. Have you pulled bullets from ammunition in same box to check powder? Not only weight but actual powder itself?
3. Bad batch of alloy or heat treatment process gone wrong.

Sincerely,
Theis

 

[whatsupdoc]

Simply replacing the bolthead is a bad idea, you have no way of checking the receiver for any defects.
I would send the barreled action back to the manufacture let them inspect it.

 

[Milo 2.5]

This action company makes “tool-less interchangeable bolt heads. They make interchangeable heads. The bolt resembles a Schultz and Larsen pattern so changing isn’t the issue, but I was asking and putting possibly myself and the incident out there for the good of future shooters whether it’s my fault or not. If it is, I accept that fully.

I also don’t want this Wonkie shit to happen again when I get said new bolt head.

Thanks for all the posts this far. I have come to most of the same potential culprits as well, myself included.

Bolt lugs are what keep us all from looking like WV hillbillies, heck, maybe even talking like one after your teeth cut your voice box on the way down.
I myself would never shoot that action again, and I get you are not me.

 

[Doug k 042414]

Yeah probably bad verbiage. Since those rounds were shooting so bad, I figured I would use them for practice then reload for an upcoming comp. I did not prepare for the “reloading Great Depression” . So I had enough resources to reload 300 rounds for my upcoming comp and load dev.

Good catch. I’ll try to provide more clarity

Hi,

So it is a 6GT and "factory" ammunition.

Which is really not "factory" ammunition; more like guy sitting at his reloading bench with IF your are lucky slightly more commercialized equipment that what everyone has at their house.

Not hard to make errors IF there is not massive oversight and operating procedures/protocols.

Now onto the bolt---
ONLY the manufacturer has the alloy spec sheets with the alloy certification sheets to compare that broken bolt to.
ONLY the manufacturer has the heat treatment spec sheets with the heat treatment certification range to compare that broken bolt to.

IMO I just cannot see enough pressure being from that 6GT case to break those lugs in itself without just a "perfect storm" of events.

1. Excessive headspace..(Did the extractor click over the base before firing?)
2. Have you pulled bullets from ammunition in same box to check powder? Not only weight but actual powder itself?
3. Bad batch of alloy or heat treatment process gone wrong.


Edited To Add:
Wait, What...I am confused. Were you shooting "factory" ammo or were you on round 299 fireforming?

Sincerely,
Theis

 

[Doug k 042414]

Bolt lugs are what keep us all from looking like WV hillbillies, heck, maybe even talking like one after your teeth cut your voice box on the way down.
I myself would never shoot that action again, and I get you are not me.

All great points! Just sucks! I’ll have to run a fall back gun.

 

[308pirate]

Do you know why they can make prefits and different bolt heads for custom actions?

Do you know why I know more about failure analysis than most people here?

Because it's part of what I've done for a living for the last 25 years or so.

Replacing the bolt head with a new one won't tell you anything about the one that failed. All it will do is introduce irrelevant and inconclusive evidence.

It's a waste of time, money, and brain cells.

But what do I know?

 

[308pirate]

I am not sure what you would have done to cause this in 300rds. I would be suspect of the bolt as Milo suggested. And as 308P suggested the best way to find out, is going to be to send the bolt head to the manufacture.

It's the only way.

 

[Ledzep]

@Ledzep what are your thoughts on this?

Primer and case head don't really look like typical bolt shearing pressure. The bolt shear looks like it was done in not many cycles (one?) and looks like pretty hard material but I'm with 308Pirate in that that's not the whole story. Lots of parts are hard on purpose. Doesn't look like a fatigue crack that propagated over time, though.

Maybe high pressure, maybe a headspace problem, maybe a bad bolt head... Can't really say anything for certain. Take pictures, don't modify anything, talk to the ammo company-- ask what pressures they run with what chamber and how they determine pressure, and send the action to the mfg., maybe arrange for a 3rd party lab to do hardness testing. These things usually go smoother when you talk it out with the mfg before you get lawyer happy but don't get bent over, either.

10 stars out of 10 would NOT just plug another bolt head in and try again.

 

[Doug k 042414]

Great points everyone. That’s why I posted it. I was completely perplexed with the issue. I am one that knows he is never the smartest dude in the room and if I ever find it, I need to find a new room! Thanks for the expertise from al of you! And thanks for legitimately caring enough to look and question. There a lot in this day and age who will just troll the shit out of people and not give it a second glance. I hate that this had to happen, but I’m happy I didn’t get “effed up” in the process.

Couple more notes on the ammo companies load

Brass- virgin hornady
Bullet in the 115 gr class
Load from five disassembled rounds varied from 38.5gr (low end) to 39.1 gr.
All rounds were pulled from different boxes that I still have. I do not have a micrometer, but with the slight red tint on the Small rifle primer, I think it might be a fed or fed match 205m (correct me if I’m just making assumptions. I know that the anvil on the CCI SRPs and SRMPs do not have a red tint to them.

Pic 1- virgin brass
Pic 2- fired brass
Pic 3- No Go gauge

As stated previously, I was sitting at 2 thou over (beyond) the no go gauge but the bolt would not fall and it started marring the barrel when I tried to apply pressure.


I’m going to reach out to both companies like many of you suggested. I will post what they tell me as soon as I get it

 

[supercorndogs]

Do you know why I know more about failure analysis than most people here?

Because it's part of what I've done for a living for the last 25 years or so.

Replacing the bolt head with a new one won't tell you anything about the one that failed. All it will do is introduce irrelevant and inconclusive evidence.

It's a waste of time, money, and brain cells.

But what do I know?

I didn't say he should replace the bolt head and carry on. I said that is how you would measure the headspace, the results would be relatively certain.

Most of time it seems like you don't know much more than your average Joe, but express wild assumptions and troll bullshit with impressive bravado.

 

[Shootin Stuff]

Just for interests sake, can you take another well lit photo of the back side of the lugs (where they sheared off) and the same again of the bolt head.

From you photos it does look like there's a colour gradient across where the lugs have separated from the bolt head, but it could just be the lighting or surface discolouration from after the event.