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

[BluntForceTrauma]

Bill Alexander would say that the Lapua brass can handle anything you can dish out — provided the chamber of your barrel is dimensioned correctly to support the case at that web area in question.

My barrels, for example, are correctly dimensioned for this.

[DeNinny]

Bill Alexander would say that the Lapua brass can handle anything you can dish out — provided the chamber of your barrel is dimensioned correctly to support the case at that web area in question.

My barrels, for example, are correctly dimensioned for this.

I would agree with that with the added provision that you stay under/at max pressure, which according to Hornady is 29.1 gr for the 123gr ELD-M.

[Klem]

I would agree with that with the added provision that you stay under/at max pressure, which according to Hornady is 29.1 gr for the 123gr ELD-M.

A grain or two either side of SAAMI probably doesn't make a difference to the OOB danger. If the base of a case is unsupported then even a half-load (25K lbs) would blow a hole in brass.

[DeNinny]

A grain or two either side of SAAMI probably doesn't make a difference to the OOB danger. If the base of a case is unsupported then even a half-load (25K lbs) would blow a hole in brass.

Not disagreeing, but if the failure is happening while still chambered, i.e. it is not OOB at the time of failure, there is still some chamber wall support as soon as the case expands to the diameter of the chamber at its widest point, giving it the necessary support to withstand failure...up until the point that the round is at max (or failure) pressure.

And also, assuming the failure is during OOB, remember the pressure is dissipating with time, so, for sure, by the time the bolt is OOB, the pressure is definitely lower than max. This might very well be 25K, but if you started with a heavier load, then it might be 26K instead of 25K at a lower starting load.

Edit: To me, the more you play around near the documented max load, you are simply increasing the risk of a kaboom relative to working with loads below max. It's a spectrum of risk.

[lazyengineer]

There is a photo out there of sectioned cases. See attached.

And there it is. Look at that Lapua on the left, look at the Hornady on the right. Then go look at OPs kaboom. THen go back and look at that Lapua case on the left again. Lapua = KaBoom; Hornady doesn't.

[Klem]

Ninny,

Not arguing that we shouldn't load within safe limits, but there's a bigger risk with an OOB at any pressure, than a hot load in battery.

Lazy,

You cannot generalize to a population with a limiting exception of one.

[DeNinny]

Ninny,

Not arguing that we shouldn't load within safe limits, but there's a bigger risk with an OOB at any pressure, than a hot load in battery.

I agree but there is always going to be higher risk at a higher pressure, all other things equal.

[lazyengineer]

Ninny,

Not arguing that we shouldn't load within safe limits, but there's a bigger risk with an OOB at any pressure, than a hot load in battery.

Lazy,

You cannot generalize to a population with a limiting exception of one.

How are intellegent experts missing this? Go look at the Lapua casing and go look at the Hornady casing - and go look at the what 4? postings now of Kabooms, that keep involving Lapua brass. Just because yours isn't kabooming in your premium barrels with your expert practices, doesn't mean this isn't as obvious as the sun on one's face; that the Lapua and the Kabooms that go to Lapua, isn't relatied to the obvious Lapua decision to run a thin web down the explody-part of the brass at the case head, and so - Kaboom. OP's Kaboom, would not have happened if he was running Hornady brass - the picture makes that strikingly obvious. Why is this so hard?

[Klem]

An alternate hypothesis is the Hornady went off in battery and the Lapua did not - and it has nothing to do with brass manufacturer - just saying.

[DeNinny]

How are intellegent experts missing this? Go look at the Lapua casing and go look at the Hornady casing - and go look at the what 4? postings now of Kabooms, that keep involving Lapua brass. Just because yours isn't kabooming in your premium barrels with your expert practices, doesn't mean this isn't as obvious as the sun on one's face; that the Lapua and the Kabooms that go to Lapua, isn't relatied to the obvious Lapua decision to run a thin web down the explody-part of the brass at the case head, and so - Kaboom. OP's Kaboom, would not have happened if he was running Hornady brass - the picture makes that strikingly obvious. Why is this so hard?

All other things equal, the strength of a metal is directly proportional to its overall weight or size. This is fundamental to all metal deformation, temporary or permanent. The more metal there is, the more force required to deform it. Again all other things equal.

So unequivocally the thicker Hornady base is going to be harder to deform than the thinner walled Lapua. Also the more curved transition from base to sidewall makes it stronger.

[lazyengineer]

here it is in four easy images









Lapua Kabooms. I won't run that. As to it being super supreme for precision shooting - eh, not really. I know plenty of trophy winning high-power shooters who consider it vastly overrated. Some who outright hate it. I don't run it - I run Norma for distance shooting in 5.56 personally.

[DeNinny]

here it is in four easy images

It's clear in this image that the head is not supported by chamber wall at the failure point. There is a gap under the bevel between the end of the lugs and the rear of the chamber. Even if this pic is not to scale, there's going to be a gap with a small amount of unsupported wall. And it will vary between barrels.

Based on this, there doesn't even need to be an out of battery scenario. The case could have failed in battery. And again, the case that will more likely fail will be the one with thinner walls or base (all other things equal).

[lazyengineer]

Bill Alexander would say that the Lapua brass can handle anything you can dish out — provided the chamber of your barrel is dimensioned correctly to support the case at that web area in question.

My barrels, for example, are correctly dimensioned for this.

This is probably true, though I can't say first hand for sure - I can say buying Grendel stuff from guys who really know Grendel (such as BFT), is probably a good start. That said, I'm an engineer and I take safety seriously. One degree of safety is a discomfort - I want two degrees. More inherently safer brass AND a more inherently safer barrel, is what I want. Lapua Brass - is not sufficiently safe for my standards. Those above 4 photos should make it very obvious why. Lapua Grendel brass is scrap.

[Klem]

Both of you are making assumptions.

Ninny,

You are assuming the quality and percentage of brass alloy is the same across manufacturers. Cartridge brass varies in quality and mix (Copper/Zinc). Here's an article from Accurateshooter.com that includes spectroscopy findings. Bottom line, thinner brass can be stronger.

Lazy,

Now, you are assuming both manufacturers cartridges went off in battery, and Lapua failed because it is inherently weaker. None of us know it was in or out of battery. Lapua's weakness, if any, is not common knowledge in the shooting community - quite the opposite. Shooters would quickly figure it out if there were more catastrophic Lapua failures such as this.

[DeNinny]

Both of you are making assumptions.

Ninny,

You are assuming the quality and percentage of brass alloy is the same across manufacturers. Cartridge brass varies in quality and mix (Copper/Zinc). Here's an article from Accurateshooter.com that includes spectroscopy findings. Bottom line, thinner brass can be stronger.

Bottom line, this is why I stated "all other things equal" multiple times. I completely understand how alloys differ in strength by chemical concentration differences. In making technical comparisons you have to analyze one variable at a time and set all the others equal. That's the only way to break down the problem.

So now to consider your point applied to this failure, the Lapua brass could be stronger due to composition differences, but I can't speak to that myself. If someone has data showing that Lapua brass is stronger in this regard, like having a higher Young's modulus or other materials deformation factor than Hornady, then I would definitely agree that composition is a factor to consider too.

Edit: I liked how the article you linked had this disclaimer:

"We do NOT have the metallurgical expertise to infer that any particular alloy shown above is “better” than another. The alloy “blend” is merely one of many variables that can have an impact on the performance and quality of the finished product. Annealing times/methods differ and some cartridge brass is extruded while other cartridge brass is made with the traditional drawing process. Readers should not presume, on reading the above chart, that they can identify the “best shooting” brass simply based on the constituent metals in the various alloys."

[lazyengineer]

Both of you are making assumptions.

Ninny,

You are assuming the quality and percentage of brass alloy is the same across manufacturers. Cartridge brass varies in quality and mix (Copper/Zinc). Here's an article from Accurateshooter.com that includes spectroscopy findings. Bottom line, thinner brass can be stronger.

Lazy,

Now, you are assuming both manufacturers cartridges went off in battery, and Lapua failed because it is inherently weaker. None of us know it was in or out of battery. Lapua's weakness, if any, is not common knowledge in the shooting community - quite the opposite. Shooters would quickly figure it out if there were more catastrophic Lapua failures such as this.

AR15s dont OOB, as the pin cannot contact the primer until the bolt is rotated into battery. In the 80,000 rounds i have fired in AR's, I have literally tested this hundreds of times in both grendel and 5.56, I'm not proud to say. Its not OOB, and fixating on that is denial of the obvious images in front of us.

There is a flat refusal to accept the obvious here - and it's not healthy. Eventually somebody is going to get hurt.

[Klem]

For goodness sake, let's all agree we just don't know enough about anything to generalize to Lapua.

[lazyengineer]

For goodness sake, let's all agree we just don't know enough about anything to generalize to Lapua.

I straight up don't agree. This is a recurring kaboom post - my "annnd another Lapua kaboom", didnt come out of nowhere.

Yours does not in your barrels - that part I agree with.

[grayfox]

Guys,
I've been reading this thread, and, while neither lover nor hater of Lapua, do not see this as some kind of endemic example of that brass' behavior. Matter of fact, 1 failure in this guy's rifle would not point, IMO, to the rifle itself either. If either the rifle or the brass were some kind of cause, I would expect more than just one failure. And from what I can tell, any faint lines talked about in other cases would not be indicative either unless those lines are appearing in the same spot and orientation as the failed case. Is that the case?

From shooting safety's perspective, a so-called "proven load" is only "proven" insofar as it is one combination of several parts and variables. ANY time you change one of the components, you should back your charge down -- some kind of meaningful amount, and build back up.

Without more instances/evidence of case damage and case failures, I would class this as a single occurrence, and put most of the weight/cause on the individual case itself. Even in a quality mfr (and Lapua is at least, a quality mfr) can have single incidents of failures. Lze, if Lapua were a "bad" mfr or one that everyone should avoid, again I think in the world of competitive and recreational shooters, I would expect there to be a much higher percentage of problems reported... with the millions of grendel loads being shot, even a 1% -- or a 0.1% -- rate would provide literally hundreds of fails. And doubtless some industry and mfr attention.

In my industry there are a few companies have a full-fledged metallurgy lab (others have access if they want it), and that kind of exam would be needed of this case in order to arrive at defendable conclusions.

You can steer clear of Lapua or any other mfr as you wish and no worries... but nothing on here that I've seen would sway me one way or the other. I don't have any Lapua and don't plan on getting any -- the cost/benefit is something I don't see in that brass for what I'm doing -- but I don't begrudge anyone else who thinks/acts differently on it. Only brass I have a negative view on is Federal in the grendel... and if I have some decent loads with it, I will shoot at unfired or 1x, it but it's too soft to keep in any kind of reloading rotation.

If you pit the flame/temperature/pressure of the powder against any brass, the brass will lose if the time in contact is long enough.

OP my advice to you is (and to any other newbies to this cartridge), like I stated earlier, when you change ANYTHING in your "proven" recipe, back off and build back up. Preferably over a chrono. This was your warning shot across the bow - take heed. The eyes/face/fingers you save will be your own. The rifle, with the new load combo in its chamber, does not care a whit about your opinions of your so-called "proven" load!!!

Never assume anything.

[lazyengineer]

https://www.65grendel.com/forum/showthre...ght=Kaboom

https://www.65grendel.com/forum/showthre...ight=Lapua

Plus this thread for Lapua brass kaboom #3
(Not sure if I missed more)

Failures tend to have near miss sign trend before. Note the countless threads about ring formation that seem heavy Lapua representation (almost all of them either Lapua or Starline). Ring formation right there in the kaboom section.