Not a great way to begin a thread on load development but....

[DShortt]

The first post has it....

I can't make heads or tails of that photo of the barrel stub end if that's what you are referring to.

If that is the case head still stuck in the barrel stub then I'm definitely thinking excessive bolt thrust.

 

[ELR LVR]

This is scary
I will throw something out there that happened to me once
Albeit I was using some "Seconds" bullets Blems, or whatever
Anyway, loading for an AR15 and just plinking rounds nothing extreme
Suddenly I felt an immense concussion of harsh recoil and my Magazine ruptured and shot out of the bottom of the magwell
I was beside myself, there was no way I used an overcharge, or the wrong powder because the previous rounds were the same exact charge and powder 26.0 grns of W-748 / 50 grn bullets
---
It really didnt hurt the rifle much but bent the extractor
Kinda hurt my hand a little, lol like firing a 500 S&W
I kept looking for further causes
Of course when I looked through the bore and saw light at the end
I dismissed an obstruction as the cause
---
Still could not find a reason
So I went to run a rod through the bore to maybe feel for something weird
I found something weird
The core on one round, had shot out, as if the base of the bullet blew out
The jacket got stuck in the bore which is relatively thin, so hard to see halfway down the bore
When the jacket stuck, the next round fired hit that jacket and caused major overpressure
I had to beat the stuck jacket out with a Dewey rod
You might inspect the bore more for something like that
or if it did happen, both obstructions could have shot out
Im lucky I was able to find the cause
I dont use "Seconds" bullets anymore

 

[shoot4fun]

It was virgin brass so straight out of the box from Peterson. Given their reputation, I would be super skeptical of something in the brass. I did have another piece of brass from them that I couldn't get in my shell holder on my primer seater. It was the only one like that. I set it aside. We micrometered hat piece of brass and it was wider at the base then the others, but all of the charged rounds fit in the shell holder else we wouldn't have been able to get the primers in them.

Happy to hear both your son and you came through this with no physical damage.
Peterson brass, at least what I have used, definitely has a bit less internal volume and this will increase pressure. The pics certainly look like the case failed, as stated above, but now was that due to a overpressure reload or a case failure?
If you have a blade micrometer you could measure the .200 line on some of the other fired brass compared to what a virgin piece measures. If the number is more than .003 more fired you are very likely at the limit of pressure.

 

[Jager]

Thanks -glad we are no one else was impacted.

We only had the one powder (8lbs of H4831SC) out when we were putting these rounds together and all of the rounds that we loaded (60+) were the same powder, so I would say very low probability it was the wrong powder.

I had two other un-fired bullets from that same string (57.4gns) which were loaded to the 57.4 charge weight. I pulled the bullets from those cartridges and weighed the powder after this even. They were both 57.4 grains so I feel pretty confident these rounds weren't overcharged. I had three more with a higher charge load. I can also take those apart and see if they are 57.7gns.

I initially thought it was a squib load (obstructed barrel), but we checked the target and the number of holes matched the number of rounds fired (except for the blow up one of course). In addition, we registered 2800fps on the last 57.1 round which I'm assuming we wouldn't have seen if the round had never come out of the barrel, so I think it highly unlikely there was an obstruction because of that.

Great info on the SEE. Wasn't aware of that. Would you think that this would have manifested itself with the other rounds that I shot before this since those rounds had lower charge weights or is there some intersection between charge weight and volume that triggers SEE? I'll do some more research on it as you piqued by curiosity (always good to learn)

Appreciate you running that through QL. Just to make sure I understand - based on QL, the loads I was shooting shouldn't have exceed safe levels (not counting out SEE). That jives with all the research that I did before deciding on the charge weights. I assume the last comment that I was a little light meant I was below the Max/Dangerous load threshold. Just want to make sure I understand.

Again - thanks for the response. Really appreciate trying to understand what happened.

Yes, S.E.E. would have been more likely with your earlier loads, since they were even lighter charges. But S.E.E. is such a rare event that that kind of correlation just doesn't happen.

To my knowledge, no one has reliably reproduced S.E.E. But it has been observed empirically for many decades, which is how we're able to correlate it with lighter loads of slow powders in higher capacity cartridges.

Yes, your charge levels were quite safe from a conventional handloading perspective... i.e. you were well under SAAMI pressure maximum. But my comment about your final round being a little light was not referring to that... it was referring to both the load density in your cartridge and to the fact that you were too far under SAAMI max.

My rule-of-thumb for slow powders is to always run them a little hot. Which is counter, of course, to the conventional wisdom of starting low and working up. An example where the thing that generally keeps us safe is the very thing that will have a gun blow up in our hands if we're not fully dialed-in to what's what.

Slow powders demand an extra measure of respect.

 

[Clabdor]

So, had you previously shot this brass in breaking in the Barrel?? Had you verified the Trim length on the Fired Brass? if the brass was overly long?? the pressure could be higher.

Never shot this particular brass. I have a lot of it.

 

[Clabdor]

Happy to hear both your son and you came through this with no physical damage.
Peterson brass, at least what I have used, definitely has a bit less internal volume and this will increase pressure. The pics certainly look like the case failed, as stated above, but now was that due to a overpressure reload or a case failure?
If you have a blade micrometer you could measure the .200 line on some of the other fired brass compared to what a virgin piece measures. If the number is more than .003 more fired you are very likely at the limit of pressure.

I'll do that

 

[Clabdor]

I can't make heads or tails of that photo of the barrel stub end if that's what you are referring to.

If that is the case head still stuck in the barrel stub then I'm definitely thinking excessive bolt thrust.

The case is still in the barrel. You can see part of the cartridge is missing (primer pocket). I outlined the base of the case with red and the missing piece in green. Hope that comes through in the pic.

 

[243winxb]

1. Stainless steel receiver or titanium?
Heat treated steel receiver failed, when not done correctly. (Sako & Tikka rifles. 2004)
2. Brass trim length to long. Crimped bullet in chamber. Seen & inspected the reloads. M70 locked. Stock split.

3. Some fancy powder thrower measures may have leftover pistol powder still in measure. When not cleaned fully.

4. Proof loads run at 93,000 PSI and dont take rifles apart.

Note- H4831 has a 10% different from slowest to fastest lots. This will not blow up rifles. https://apps.dtic.mil/sti/citations/ADA572333

 

[Clabdor]

This is scary
I will throw something out there that happened to me once
Albeit I was using some "Seconds" bullets Blems, or whatever
Anyway, loading for an AR15 and just plinking rounds nothing extreme
Suddenly I felt an immense concussion of harsh recoil and my Magazine ruptured and shot out of the bottom of the magwell
I was beside myself, there was no way I used an overcharge, or the wrong powder because the previous rounds were the same exact charge and powder 26.0 grns of W-748 / 50 grn bullets
---
It really didnt hurt the rifle much but bent the extractor
Kinda hurt my hand a little, lol like firing a 500 S&W
I kept looking for further causes
Of course when I looked through the bore and saw light at the end
I dismissed an obstruction as the cause
---
Still could not find a reason
So I went to run a rod through the bore to maybe feel for something weird
I found something weird
The core on one round, had shot out, as if the base of the bullet blew out
The jacket got stuck in the bore which is relatively thin, so hard to see halfway down the bore
When the jacket stuck, the next round fired hit that jacket and caused major overpressure
I had to beat the stuck jacket out with a Dewey rod
You might inspect the bore more for something like that
or if it did happen, both obstructions could have shot out
Im lucky I was able to find the cause
I dont use "Seconds" bullets anymore

Wow...glad you didn't have any injuries from that. Thanks for the response. I did the same thing after we kind of got over our shock. Looked down the barrel - saw nothing but light. I'm thinking I might take this to a gun smith and put a bore scope down the barrel to see if, indeed, some fragment got embedded in the wall.

I did post some pics of the rounds that were fired right before the blow out and while I'm not expert, I didn't notice any swipe marks, primer flow, etc..that would have led me to believe the previous rounds were approaching the red line. There are some super knowledgeable and experienced people on this forum & thread and if someone sees something and I just missed it, I would appreciate y'all pointing it out to me. I actually look after each round when I'm doing this to see if I notice anything.

 

[DShortt]

The case is still in the barrel. You can see part of the cartridge is missing (primer pocket). I outlined the base of the case with red and the missing piece in green. Hope that comes through in the pic.

So that round 'protrusion' on the right is probably exactly where the ejector is and the missing section is where the ejector was.

Definitely EXCESSIVE bolt thrust.

 

[Clabdor]

So that round 'protrusion' on the right is probably exactly where the ejector is and the missing section is where the ejector was.

Definitely EXCESSIVE bolt thrust.

Good to know. Now trying to figure out how not to have that happen in the future.

You mentioned excessive bolt thrust can be caused by such things as neglecting to remove the case lube or too fine a finish on the chamber walls.

Since this was virgin brass would there have been the possibility of excessive case lube from the factory? I say that because I pulled it straight out of the sealed boxes from Peterson and loaded them.

If you have time, can you expand on the finish on the chamber walls?

Would appreciate any advice on anything else I need to be watching for in the future?

Thanks to all for digging into this. Learned a lot so far.

 

[Clabdor]

This is an interesting read. Thanks for pointing out the bolt thrust.

Thread 'Bolt thrust'

Feb 24, 2023

Why is it "bad"?
Will it cause lugs to fail? Or just increase head space?
If so how many rounds?

I'm just trying to get a handle on the physics, mechanics of this
No No.

• TAJ45
• Replies: 78
• Forum: Main Message Board

• 

 

[Clabdor]

For my education, does anyone see excessive signs of pressure on these cartridges? These were the rounds fired before the blow up.

 

[DShortt]

Good to know. Now trying to figure out how not to have that happen in the future.

You mentioned excessive bolt thrust can be caused by such things as neglecting to remove the case lube or too fine a finish on the chamber walls.

Since this was virgin brass would there have been the possibility of excessive case lube from the factory? I say that because I pulled it straight out of the sealed boxes from Peterson and loaded them.
It
If you have time, can you expand on the finish on the chamber walls?

Would appreciate any advice on anything else I need to be watching for in the future?

Thanks to all for digging into this. Learned a lot so far.

It is entirely possible that some sort of residue was present on the new brass. I would suggest wiping down the case walls with a solvent such as denatured alcohol before priming any brass, new or used, going forward. Dispose of the rag/towel in such a manner as to control fumes in the area.
As far as the interior chamber wall finish, that's going to be difficult to determine at this point.
I can tell you, many 'smiths use abrasive paper to put a 'cross hatch' type finish on the chamber wall where the case body contacts it to ensure good 'adhesion' during the firing cycle.
I have no idea what the manufacturer of this rifle did and given the circumstances, it will be difficult at best to determine now.

Given that you fired several rounds previously without any problems, I would tend to suspect one case in particular was contaminated, but again. It's difficult to be certain at this time.

 

[243winxb]

Heat treat fail?

Titanium rifle receivers, commonly made from Grade 5 (Ti-6Al-4V), require specialized heat treatment to optimize strength, fatigue resistance, and durability, often reaching hardness levels of 30-40 HRC.

 

[ELR LVR]

For my education, does anyone see excessive signs of pressure on these cartridges? These were the rounds fired before the blow up.View attachment 1738179

I see some primer cratering, but no primer "Flattening"
Signs of being at the upper limit
but not excessive
---
I see no shiny Ejector marks on the rim
---
is it possible? you "LIGHT" charged one by accident
powder measure started running low and didnt catch it?
and a flashover happened over the whole powder charge
---
I've ran low before and didnt catch it and then had to go back and weigh like 100 cases to find the 2 light ones

 

[ronsatspokane]

Just looking at the pictures and the fact I'm not familiar with CA rifle it looks to me like like the case failed and blew the extractor out. This allowed the gasses to overpressure the action behind the barrel and in front of the lugs. The action failed and released the barrel. There are normally holes in that region to vent but I'm not sure just how well the work in a catastrophic case failure. The velocity is low because gas was released during bullet travel. The barrel pressure was lower.

Best 1st guess as to cause is severe overpressure. Loaded same time as your son's load? Did you recharge the powder measure during reloading?

I concur with this. In looking a your fired brass, I do see rather heavy cratering of the primers on that one set of rounds of 5 in a row. If you were way over pressure though the next thing I would expect to see are very flat primers or blown primers and perhaps smearing due to heavy bolt lift. This looks like a case failure. The only thing I can think of would be defective brass or a barrel obstruction like a jacket lost and left in the bore. I've only lost jackets after the bullet left the barrel however.

 

[nakneker]

Wow! Glad you and your boy didn’t get hurt, serious pucker factor!

 

[Murray Brook]

is it possible? you "LIGHT" charged one by accident
powder measure started running low and didnt catch it?
and a flashover happened over the whole powder charge
---
I've ran low before and didnt catch it and then had to go back and weigh like 100 cases to find the 2 light ones

Could certainly be the culprit. This could cause the SEE thing, not a normal charge of the slow burning powder. Glad you and your son are good.

 

[One Eye Pete]

Thank the Good Lord no one was hurt.
Since I am only looking at pictures I can only speculate as to what happened. Also although I am a mechanical engineer by trade most of my work was on power plants (at much lower pressures) so I really can’t profess to be an expert on the mechanics of rifle actions.
Looking at the cases from your previously fired rounds I don’t see any signs of overpressure. Since you were reloading with only one powder and one type of bullet it is unlikely that the wrong powder, or wrong bullet was the cause. Since the previous bullet showed up on the chronograph and impacted on the target it is unlikely that the barrel was obstructed. Especially since you could see down the barrel after the final shot. The fact that the bore was clear and you got a reading on the final shot tells me the bullet left the barrel. What I found quite odd was that the second to last shot registered approximately 2800 and the final shot 2600 and yet the action let go. I did a quick check on Gordon’s Reloading Tool and even if the powder charge was slightly off, say 1/2 to one grain higher, it seems that you would still be in a safe range that certainly shouldn’t destroy an action.
The other thing I find odd is that bolt thrust is generally straight back against the action lugs yet this doesn’t seem to be how the action failed. Outward thrust from the brass case is normally against the barrel chamber walls and constrained by the barrel itself and yet it doesn’t seem as if the barrel is bulged. You might want to take some micrometer readings on the barrel to confirm it is not bulged. The way the receiver failed it almost strikes me as if the case failed first releasing the expanding gasses between the bolt and the action splitting the action apart the way it did. Yet the problem with this theory is that the venting holes in the sides of the receiver should have vented the escaping gasses limiting the pressure rise. Even normal chamber pressures in the 55,000 psi range is probably more than enough to do serious damage if defective components fail.