09-22-2022, 06:20 AM (This post was last modified: 09-29-2022, 02:57 PM by LRRPF52.)
First time I've had this happen in 30+ yrs of reloading. I was at the range yesterday doing some prep for the coming mule deer season in WA, when i had a catastrophic failure in round #41 in a box of 50 handloads. I was shooting offhand - first shot of 5 in a mag, and at the shot, the magazine was forcefully ejected, the floorplate was blown out of the mag, and spring, follower, and the other 4 rounds went forward of the line. Lots of "extra" gas. No injury to report other than the initial shock. The load I was using was as follows:
123gr ELD-M
CCI #41 29.4gr AA 2520 (dropped from Redding BR Powder measure - these averaged between 29.35 to 29.6 in the sample set I took - 29.6 is a listed max in the Accurate load book)
Lapua cases (new)
OAL: 2.245"
The gun is an Aero framed pistol built around an OdinWorks 12" barrel with a Midwest Industries rail. The bolt looks fine, but I will be checking headspace and internals with a borescope. The magazine was bowed out a bit on the sides where the floorplate was - I was able to bend it back together, and it test fired great later in my 18" Faxon/Aero. Magwell looks fine so far, but will investigate more when I clean it up.
The plan is to drop this load back a grain or so to 28.5 (Saw this was a fave of DianeB). Rats - 160 some rounds I'll need to pull Either that or save them for a bolt gun I need to eventually buy.
I would guess this round had the old powder measure slip open and add a bit of pow-pow gradually - some of the other rounds near this one had a slight line developing around the case head. I will post pics later if I can get a good close-up.
QL is predicting your load is 64K lbs (Grendel SAAMI is 52K lbs). 106% case full is crunching powder when you seat the bullet. Pressures increase exponentially when powders are being compressed, and also less predictable as you change the burn characteristics. 2520 is a bulky, slow powder for Grendel out of a short barrel. The case becomes full before the powder becomes compressed.
I'd be loading no more than 27.8 which is exactly 100% full and right on the SAAMI pressure limit for 2520.
Something else happened if your case head opened up. This was an 80KPSI+ event (more like 120KPSI)! Wrong powder, wrong bullet, obstructed barrel, massive over-charge, something major happened. You don't need to simply drop your charge by a single grain.
Do you have any velocity measurements?
Re-weight your powder charges in your cases as you take them apart. Put the same powder back in your powder measure and re-weigh the charges.
stonehog Wrote:First time I've had this happen in 30+ yrs of reloading. I was at the range yesterday doing some prep for the coming mule deer season in WA, when i had a catastrophic failure in round #41 in a box of 50 handloads. I was shooting offhand - first shot of 5 in a mag, and at the shot, the magazine was forcefully ejected, the floorplate was blown out of the mag, and spring, follower, and the other 4 rounds went forward of the line. Lots of "extra" gas. No injury to report other than the initial shock. The load I was using was as follows:
123gr ELD-M
CCI #41 29.4gr AA 2520 (dropped from Redding BR Powder measure - these averaged between 29.35 to 29.6 in the sample set I took - 29.6 is a listed max in the Accurate load book)
Lapua cases (new)
OAL: 2.245"
The gun is an Aero framed pistol built around an OdinWorks 12" barrel with a Midwest Industries rail. The bolt looks fine, but I will be checking headspace and internals with a borescope. The magazine was bowed out a bit on the sides where the floorplate was - I was able to bend it back together, and it test fired great later in my 18" Faxon/Aero. Magwell looks fine so far, but will investigate more when I clean it up.
The plan is to drop this load back a grain or so to 28.5 (Saw this was a fave of DianeB). Rats - 160 some rounds I'll need to pull Either that or save them for a bolt gun I need to eventually buy.
I would guess this round had the old powder measure slip open and add a bit of pow-pow gradually - some of the other rounds near this one had a slight line developing around the case head. I will post pics later if I can get a good close-up.
StH:
You are describing an out of battery firing to the letter. Have had it happen to me twice with the Grendel. Not once with any other cartridge.
If you didn't bump that one piece of brass enough, maybe that is the cause. Or have a bullet seated a bit too long. Could be it short cycled just a tiny amount.
The problem with out of battery firings is no one can ever find out exactly why.
I doubt it was overcharged although I doubt I would go with over 29 grains of 2520 with the long bullets.
Something else happened if your case head opened up. This was an 80KPSI+ event (more like 120KPSI)! Wrong powder, wrong bullet, obstructed barrel, massive over-charge, something major happened. You don't need to simply drop your charge by a single grain.
Do you have any velocity measurements?
Re-weight your powder charges in your cases as you take them apart. Put the same powder back in your powder measure and re-weigh the charges.
Hornady says 29.1 grains is max with that combo, but both QL and GRT say that's a 64,000 plus PSI load.
09-22-2022, 09:39 PM (This post was last modified: 09-22-2022, 09:43 PM by lazyengineer.)
LR1955 Wrote:StH:
You are describing an out of battery firing to the letter. Have had it happen to me twice with the Grendel. Not once with any other cartridge.
If you didn't bump that one piece of brass enough, maybe that is the cause. Or have a bullet seated a bit too long. Could be it short cycled just a tiny amount.
The problem with out of battery firings is no one can ever find out exactly why.
I doubt it was overcharged although I doubt I would go with over 29 grains of 2520 with the long bullets.
Join the club.
LR-55
With respect - I am starting to suspect this is one where the manufacturer cut the brass where web head is cutting it close in depth to the chamber exposed section to maximize volume capacity, with metallurgy and practice that lossens up over time with multiple hot loads. Almost every kaboom here is a Lapua or Starline multi fired case - always looks like OOB - A kaboom type and route that basically never shows up in 5.56 in same platform. AR15 is hard to OOB.
I've seen way too many of these kaboom posts - always lapua or starline
muvef Wrote:Hornady says 29.1 grains is max with that combo, but both QL and GRT say that's a 64,000 plus PSI load.
Nosler says 29.5 grains with their 120 gr BT.
Weird.
The difference is that Hornady, Hodgdons, Alexander Arms, Sierra, etc. actually tested their loads in calibrated pressure test breeches, whereas QL and GRT entered numbers into a theoretical program with no actual measured data, which is meaningless and invalid.
The Alexander Arms published max load with Lapua brass even with 129gr SST is 29.4gr of AA2520, CCI450, 2.260 COL.
123gr Scenar max load with AA2520 from AA data is 30.7gr using CCI450, 2.260 COL.
From Hodgdons, its 29.5gr under 123gr Scenar at 2.260, using Winchester SRP and Alexander Arms brass (Lapua) 51,800psi.
Hodgdons also shows 29.6gr AA2520 under 123gr SMK at 51,700psi.
Nosler shows 2.245 COL with 120gr Nosler Ballistic Tip, Nosler brass, Rem 7.5 SRP, 29.5gr max.
52,000psi isnt going to cause case failure in brass thats rated to at least 60,000psi yield strength, which has a Factor of Safety built into that number as well.
We need to see the case.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
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lazyengineer Wrote:Been here 2 years, this is the 4th or 5th kaboom. The number of kaboom's/user/unit time is stunning. Common demoninator is lapua/starline.
Lazy,
Lapua is all I use in this calibre. No brass failures.
If you have had 4 case separations then I would be looking elsewhere for the reason. I have had two case separations in my shooting career, both on the same day (not Lapua). I knew almost nothing about headspace at the time and that was definitely my fault for bumping them too hard.
For the thread, I agree, we are just speculating without seeing photos of the brass and bolt - and 52's discovery of the bad batch.
I didn't feel this was a compressed load, and I always visually inspect the level when seating to make sure it's not a squib. Now, I could have spaced one I guess, but I will have to check a few in the box and see what I find. I need to get a puller so it may be a few days before I can investigate that side. [ATTACH=CONFIG]19114[/ATTACH]
I cleaned up the rifle and bore-scoped it - no issues I could see in the lugs or barrel throat. I checked headspace, and it looks like the bolt now fully seats on the no-go gauge. I replaced the bolt with a spare Monster, and it's back to spec. Hopefully the image loads this time. The image size limits on the forum are a bit small...
09-23-2022, 03:15 AM (This post was last modified: 09-23-2022, 03:46 AM by Klem.)
Stone,
The split in the photo is lower than typical for case separation (too much headspace), or incipient case separation (gradual work hardening from too much repetitive stretching).
In your case the split is right down at the end where the brass is thickest, and only on one side. This suggests headspace was correct and the round was in battery. The brass expanded as normal and was supported by the chamber, but kept expanding and failed at the weakest point of support at the time - the extractor. There is no lug at the extractor. Looks like it was in battery and an over-pressure situation took the path of least resistance, out past the missing lug and back into the receiver. Then, continuing path of least resistance down the magwell.
Unsurprising the bolt is now out of spec with the No Go gauge. For brass to split at its thickest part implies a huge hammer blow to the bolt face and lugs before pressure release. The barrel extension will have copped the same thump. Once stressed, steel can become brittle and fracture, but in some situations compression from a detonation can actually make it stronger. In this case, my money would be on the event having stressed the extension. In an AR that means the barrel has to go as well. That is expensive, so up to you where you go from here. I would pull, weigh, and measure every single round from that batch.
Either that or save them for a bolt gun I need to eventually buy. 
![[Image: recallacc2520.jpg]](https://accurateshooter.net/pix/recallacc2520.jpg)