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

[LR1955]

https://www.65grendel.com/forum/show...ghlight=Kaboom

https://www.65grendel.com/forum/showthread.php?25200-Qwik-load-help-requested-I-BLEW-ONE-UP!&highlight=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.

LE:

I think you understand statistics. Are you positive the populations of brass are identical, the loads identical, the firearms identical, the types and conditions of the shooting among all of the types of brass are identical? Only then can you say that Lapua brass is weaker than others. You know this, I am sure.

Right now you have anecdotal evidence only.

There is a reason Lapua has garnered a reputation among competitive shooters over the decades. It is considered the best quality brass being made today.

LR-55

[lazyengineer]

LE:

I think you understand statistics. Are you positive the populations of brass are identical, the loads identical, the firearms identical, the types and conditions of the shooting among all of the types of brass are identical? Only then can you say that Lapua brass is weaker than others. You know this, I am sure.

Right now you have anecdotal evidence only.

There is a reason Lapua has garnered a reputation among competitive shooters over the decades. It is considered the best quality brass being made today.

LR-55

I understand safety at the field level, and the engineer is responsible for the system safety he develops or endorses.
I see trend specific to one component, and compelling explanation, combined with a large body of near-miss warning signs .

When you see a failure mode trend, and then see a difference that readily explains that failure mode - you call it out.

What I am also seeing, is what I see at the field level safety - of experts who have always said it is one thing, are the slowest to see the obvious when pointed out, and counter to their own bias.

Go look at those 4 photos, look at the fact that 3 kabooms in the last year - only with that brass, amd look at the warning tell of the ring shoulders. I'd fire an engineer who didn't call this out. It might also only fail in certain barrel at certain gas settings. Are you OK with that? I'm not.

[grayfox]

ok. I see 2 circumferential separations, clean-circumferential... one with powder could be over-loaded with a 120-gr bullet loaded tight or in the lands (AR comp has more variation in powder loads than most powders I use, and I use AR comp in the grr and 27.7 in one of my lots... is over), and 1 circumferential case separation in a wildcat with fatigued brass (20-25x loads) admittedly in unknown pressure/load arena for his charge...
Still don't see a generalizing pattern. Unless we point to 3 loads that were at least suspect or over-charged... or something like that.

This one by OP is, well, not circumferential. Looks pretty axially aligned to me. And not in the same spot.

The 2 examples you cite, don't point to any problem with the Lapua's bottom "right-angle" corner either. The failures are up away from that area. So guess I don't see a generalization there on Lapua construction down at that corner...

[grayfox]

The other thing I might generalize from these 3 examples is, bad or poor load practices by the shooters.

Hate to quote John Wayne here, but you can't fix stupid. A nicer way to say it (from my own background), nothing is sailor-proof.

[Klem]

Why stop at the brass manufacturer, why not slam the calibre? They all happened in a Grendel - Grendels are inherently dangerous.

The likelihood Lapua is the cause rather than the symptom is remote.

[DeNinny]

grayfox (and Klem) I understand all of what you say. Clearly there is not enough statistical data regarding this failure to be outright proven, but note that there is not enough data to prove the otherwise or any other failure as well. All of us can only speculate and give our subjective opinions here (which to me is the point...and fun!). It goes both ways with point and counterpoint on a technical debate. As an engineer I am just working with the "data", albeit anecdotal, that's just available in the moment. And of course we should have other failure models on the table here and keep them open too.

And just to be clear on my position/current opinion, I definitely think OP was running a hot load. He was above Hornady's max load with a Hornady bullet. His casing could have easily been Hornady or Norma and still fail.

Also I agree about Lapua being too expensive to be worth it.

[BluntForceTrauma]

[DeNinny]

BluntForceTrauma forgive my ignorance, but how does one know the type of feed cone they have for their barrel? How does one know if their barrel has a cone that goes deeper into the chamber than another barrel's cone?

To me, this area, while the round is in battery, is clearly where the case is unsupported. And theory says that the bigger this exposed area, the higher the chance of it promoting a failure under high pressure. All other things equal.

[Zeneffect]

Alternative 3... very far fetched and completely fictitious

Latest batches of lapua are fakes/knock off. At $1 a case and being oh so close to 7.62x39 a Chinese factory has figured out how to make a blue box for profit.

Enjoy the chuckle.

[LRRPF52]

Thank you. No extrusion evidence of gross overpressure. Solid primer strike with a deep impact, which you can only get in an AR15 with a fully rotated bolt. Brass blowout and peel back right at the seem between the web and the body. That brass failed because that brass wasn't supported by a steel chamber wall there. Meaning the chamber cut was too short (too much bevel), the brass head wasn't thick enough to cover that spot with strong enough solid brass head at that depth, or the bolt started unlocking and moving exposing that spot of the brass while still under pressure. Or a tolance stack of all 3 of those combine juuust enough, to kaboom. The correlation this seems to occur only with certain brands, is an item of note.

Section one of your lot of casings and another brand like Hornady, and take a hard look at the head, web, and transition between the two. And any different in how easy each was to cut.

You do you - I've seen this enough times now that when I pick up Lapua Grendel brass - I either scrap it, or run it as a mild fire/forget field load

[Zeneffect]

12" barrel, decent charge of a slower burning powder.

Anyone run this setup over quickload to see what pressure is at the port? I bet it's pretty damn high (regardless of software accuracy.) Early unlock and blowout maybe? Maybe you can gain more dwell with a pigtail tube and let pressure drop a bit more.

[LRRPF52]

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.

against Lapua by a factor of 2-5:

[lazyengineer]

I'd say that's a balanced answer. Obviously Lapua has served the more expert members here with proper chambers and gas settings very well, and will continue to do so. For general shooters with potential from a broad spectrum of barrels and such, there is potential for tolerance stacking to become our 4th 2021/2022 Lapua Kaboom, to a degree a general shooter new to this game should be aware of. Safety is everybody's business.

[LRRPF52]

grayfox (and Klem) I understand all of what you say. Clearly there is not enough statistical data regarding this failure to be outright proven, but note that there is not enough data to prove the otherwise or any other failure as well. All of us can only speculate and give our subjective opinions here (which to me is the point...and fun!). It goes both ways with point and counterpoint on a technical debate. As an engineer I am just working with the "data", albeit anecdotal, that's just available in the moment. And of course we should have other failure models on the table here and keep them open too.

And just to be clear on my position/current opinion, I definitely think OP was running a hot load. He was above Hornady's max load with a Hornady bullet. His casing could have easily been Hornady or Norma and still fail.

Also I agree about Lapua being too expensive to be worth it.

[LRRPF52]

12" barrel, decent charge of a slower burning powder.

Anyone run this setup over quickload to see what pressure is at the port? I bet it's pretty damn high (regardless of software accuracy.) Early unlock and blowout maybe? Maybe you can gain more dwell with a pigtail tube and let pressure drop a bit more.

QL is useless in this respect, for reasons we have covered before. QL can misrepresent an actual 49,000psi load as 64,000psi. The 49,000psi data will have come from a pressure test breech, whereas QL came from someone generating a software model, never having touched an instrumented breech for that specific case.