I had a partial case head separation using a 1.8oz buffer

[stonehog]

The three I have shown individually were the ones I could see a ridge forming on. The rest look pretty normal albeit a bit rough from the chamber. I don't see this sort of chamber imprint on the other brass I've inspected (FC, Starline, Hornady) so far. My bet is the odin chamber is a bit rougher than the Faxon or PSA. I also looked back at notes showing that I had checked headspace with the Odin BCG and bolt in the Faxon barrel (passed) but I don't see notes that I ever checked the Odin bolt in the Odin barrel. Doh! I probably expected it to be OK as it was a matched barrel and BCG/Bolt purchased. It will be interesting to see if I get similar extraction issues and/or brass markings with the Monster bolt I am replacing it with (that has passed headspace).

BTW - thanks for all the deep dives here folks - I'm learning a ton about both the AR platform as well as the Grendel. Good stuff!

[lazyengineer]

Lazy,

The only thing 'staring us in the face', are the pieces of a catastrophic failure, and even in that there is a lot of information missing. For example, how the round was assembled by the OP at the time and its actual specs. Yes, that Lapua case failed, but that does not prove it is the cause. It could be a host of other reasons that have nothing to do with the brass manufacturer. And until you can rule out all other possible causes you cannot say with confidence it was Lapua's fault.

The only other potential cause you can confidently rule out is Hornady, and every other gun manufacturer, every other powder and powder manufacturer, etc. Yes, it was not a Hornady case in the breech at the time. But that does not prove which brass is stronger. It is just one piece of evidence.

That the case was Lapua and implying it was the cause, then generalizing to all Lapua brass beggars belief. Please stop with the Lapua hate, it is hijacking the thread.

In the last 12 months, 3 Kabooms - all with Lapua Brass. Lapua brass represents... what, 10% of all fired brass (not hardly, but we'll just say that.

N = 3.

First Kaboom = 10% chance of having been with Lapua (if Lapua is 10% of all fired reloaded brass). ALL 3 kabooms to exclusively be Lapua? For all 3 kabooms to all mysteriously be Lapua, is 0.10^3; which is a 1 in 1000 chance, if Lapua is 10% of all reloaded brass (which it very much is not). None of the 3 kabooms show sign of overpressure or OOB. The refusal to recognize the remarkable odds of such a coincidence; combined with the painfully obvious difference in case construction at the very location of each failure is difficult to understand.

[DeNinny]

I understand all of this, but it doesn't necessarily mean that Lapua brass can't have a lot of reloads AND also it could have contributed to the issue. And it goes back to an earlier post where I stated that brass that is more malleable and elastic but also has lower hardness and yield strength than Lapua could have been a better brass in this specific failure case which is partially due to the M16 style feed cone depth issue. As stated before, a harder and higher yield strength brass is going to be more brittle than one that is more malleable and elastic with also lower hardness and yield strength. And so under extreme forces (i.e. pressure) the more brittle brass can simply snap and rupture, but a more malleable and elastic brass could stretch a little bit more than the harder and stronger one. This is entirely theoretically possible while also the same brass doesn't last as long with subsequent reloads.

And all this is in line with Lapua brass lasting so long! It literally resists deformation better than other brass, so it can be reused more often. I totally don't doubt this, but...I can also say that it could also be more susceptible to failing like it did than other brass as well. Due to it being slightly more brittle than other brass. With all metals and alloys you get this duality at times. There's no perfect one vs another. When you use one you likely have to make a tradeoff or compensation that another metal would provide. But then that metal might also have a different compromise.

I digress here but the making of samurai swords and carbon steel is a good example. Too much carbon and the steel becomes really hard, but then it is more brittle (less elastic). Take away some of the carbon, and it becomes less hard and more malleable and elastic. Same thing is going on with brass at different alloy compositions.

[Klem]

Stone,

Understood, only a few cases are showing expansion forward of the web.

Here's a thought. Sheridan sell a rifle gauge that has been reamed to SAAMI spec. Lyman and others tend to be a bit generous in diameter to ensure all cases measure longitudinal headspace, and not give false longitudinal indications because fat bodies are jamming in the mouth. If your enlarged spent cases do not seat fully to the shoulder in a Sheridan gauge then there is too much slop in the breech.
Sheridan - Copy.jpg

Those Lapua cases have had countless firings, at least over 10 each.

(Disclosure: I am not Sheridan Manufacturing but was given those two gauges for comment).

[Klem]

Lazy,

Your statistical conclusion is flawed.

I have had no Lapua kabooms...ever. How does that reconcile with your experience?

[DeNinny]

Agreed and appreciated. LOL I work with all kinds of engineers and technical people, and trust me they all can have differing opinions about diagnosing the same problem. This exchange is a typical day at work for me. The only (obvious) rule for everyone is to use data and the laws of science to back your position. And be open to being mistaken on your own understanding.

Also, being new here and coming from Reddit, there is absolutely no way I could get technical over there like I am here. Over here, I'm with my people. We are all part of the Horde and so we are all on the same team! And we don't even have to agree on everything. That's no fun.

Understood on all. The 5.56 cartridge is also smaller diameter than grendel, so absolutely it will withstand higher pressures than grendel (all other things equal). The lower radius and lower size to brass volume ratio makes it stronger on a pound-for-pound basis. Again it's like an archway analogy that I mentioned before.

So with this I'm sorry I stated that the grendel round had to be designed to withstand higher pressures. That was incorrectly phrased. What I really meant is that its less curved case wall due to higher diameter needed to have more support. Hence, the Bill Alexander feed cone redesign. I hope we are on the same page about it now. Again, I never cared about the pressure itself. I only cared about what Bill Alexander was addressing when he redesigned the feed cone.

I provided numerical data, namely the fact that millions of 6.5 Grendel Lapua brass and ammunition have been manufactured and fired and reloaded from 2004-present.

The data I'm looking for here is the failure (or lack thereof) data for Lapua brass used with M16 style feed cone barrels in AR15 platforms. And I'm also looking for comparison data on this amongst all the various grendel brass manufacturers. I always need the comparison data! Not just one manufacturer's.

And again I don't see comparative actual performance data under the specific condition of this failure. And in lieu of not having this data, the next best thing to me is to have the specific materials science parameters that I mentioned...Young's modulus, shear modulus, hardness, yield strength.

And I know all this data is a tall order and will likely never be produced. And this is why I'm leaving the conclusion open ended. I'm not saying it's definitely Lapua brass as a contributing issue, and I'm not not saying it too!

[lazyengineer]

Lazy,

Your statistical conclusion is flawed.

I have had no Lapua kabooms...ever. How does that reconcile with your experience?

That is a staggering assessment. My Rocket has not crashed with my 0-rings from the same manufacture. Therefore the 0-rings are safe.

That is literally the allegory just stated.


There seems to be a misplacement of interpretation. This isn't about you. It's not about your practices, your barrels, or your brass. Your practice and example is not representational of the general population - as we have seen; 3 times now. There is a defensiveness being taking here that some peoples personal decisions to run Lapua safely in their systems, is somehow under attack. It's not; and it is highly unlikely you will experience problems, as your practices and equipment likely are better managed and controlled. Meanwhile, the rest of the general population, who aren't you, have blown up 3 times now. My concern is there is a refusal to see the obvious trend; and it's done by a defensive reaction to personal individual experiences. It's a blind refusal to see the obvious, based really in truth on that shocking analysis I just quoted - that I NEVER expected to see posted like that.


Also, please correctly run the statistics on the odds of 3 Kaboom's of 6.5 Grendel in the last 12 months; with all 3 to exclusively involve only Lapua brass. I look forward to seeing what the odds are of that by your assessment.

[DeNinny]

More photos. I was only able to find the slightest ridge forming on 2 cases. #9, and #36. #41 was the kaboom.

Assuming you didn't have significantly different loads in these rounds, these pictures indicate you were pushing the pressure limits of this brass...with all the other issues in effect as well...deep feed cone, deep bolt face, headspace, etc. You were close to the failure limit, but not in massive excess of it. So only a few rounds instead of all of them deformed beyond the norm.

Also the pics still keep heat on the table too. As you were shooting, the barrel was heating up which was heating up the rounds and the starting temperature of the combustion. Towards the end of your batch the barrel would be warmer, so your risk of failure kept going up.

[DeNinny]

The three I have shown individually were the ones I could see a ridge forming on. The rest look pretty normal albeit a bit rough from the chamber. I don't see this sort of chamber imprint on the other brass I've inspected (FC, Starline, Hornady) so far. My bet is the odin chamber is a bit rougher than the Faxon or PSA. I also looked back at notes showing that I had checked headspace with the Odin BCG and bolt in the Faxon barrel (passed) but I don't see notes that I ever checked the Odin bolt in the Odin barrel. Doh! I probably expected it to be OK as it was a matched barrel and BCG/Bolt purchased. It will be interesting to see if I get similar extraction issues and/or brass markings with the Monster bolt I am replacing it with (that has passed headspace).

BTW - thanks for all the deep dives here folks - I'm learning a ton about both the AR platform as well as the Grendel. Good stuff!

Do you think you could take a measurement of the depth of the head deformation? Basically what is the distance from the "line" to where the bolt starts? This will be a measure of the exposed and unsupported brass wall. With your actual deformed brass we can determine the feed cone depth!

It's interesting that your other brass doesn't have the same imprint. Only the Lapua. Hmmm...

And I totally appreciate you sharing all this! I'm learning and enjoying this thread too.

[StoneHendge]

I understand. I made the point because BluntForceTrauma stated that there is no spec on it. And I'm just saying that *if* it did have a spec, then customers could reject a barrel based on it and also the manufacturer would have more incentive to check and make sure their barrel wasn't effed up before it made it out of the production line. Another way of looking at it is without a spec then there's less quality control over the making of it. And you wouldn't be able to hold a manufacturer accountable if they effed one up.

I hear you. I was more using your comment as a base for mine - there's a lot of mental masturbation in this thread. Lack of a spec for the feed cones is really more of a SAAMI issue - I don't blame Bill Alexander for keeping his proprietary to maximize revenue from his efforts.

What would be useful is if the OP was able to get a picture of a sized case in the Odin chamber and in the chamber of one of his other barrels. I know that's extremely difficult, but it would be very telling.

[Klem]

Also, please correctly run the statistics on the odds of 3 Kaboom's of 6.5 Grendel in the last 12 months; with all 3 to exclusively involve only Lapua brass. I look forward to seeing what the odds are of that by your assessment.

...Lapua is unsafe in your loads, but not mine? Conclusion:
1. Lapua is unsafe.
2. Your handloading is unsafe.

(Hey, you did ask)

[lazyengineer]

...Lapua is unsafe in your loads, but not mine? Conclusion:
1. Lapua is unsafe.
2. Your handloading is unsafe.

(Hey, you did ask)

This is pointless.

Kaboom 1 - Lapua in an AR15 with an Odin BBL by one user

Kaboom 2 - Lapua in a bolt action rifle by another user

Kaboom 3 - Lapua in an AR15 with a PSA BBL by yet another user


All other brass: No Kaboom.
Lapua represents a small portion of reloading brass in use; and has an engineering aspect different from all others, at the location of Kaboom's

Conclusion - Lapua can't be a component of that?

[Klem]

Lazy,

I did not say it was Conclusion 2 - I just pointed out the logical conclusions.

You have had three Lapua kabooms in 12 months while I have not had any in 30 years. I did ask you to reconcile the difference given you are blaming the manufacturer and not entertaining it could be you (and 'friends'). If you are not going to reconcile it by stating the obvious then again, please, stop polluting the thread by involving the public in blame-shifting.

[lazyengineer]

Lazy,

I did not say it was Conclusion 2 - I just pointed out the logical conclusions.

You have had three Lapua kabooms in 12 months while I have not had any in 30 years. I did ask you to reconcile the difference given you are blaming the manufacturer and not entertaining it could be you (and 'friends'). If you are not going to reconcile it by stating the obvious then again, please, stop polluting the thread by involving the public in blame-shifting.

So... you are saying bad reloaders pick Lapua? I wonder what the statistical odds are of all 3 of the kabooms in the last year are, of only being Lapua?

[Klem]

So... you are saying bad reloaders pick Lapua? I wonder what the statistical odds are of all 3 of the kabooms in the last year are, of only being Lapua?

Significant in your case - insignificant in the wider community.

Can you please accept that one possibility is that you are responsible for your own kabooms, so we can move on.