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

[stonehog]

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.

[Klem]

That is a hot, compressed load.

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.

What does the case look like?

[Happy2Shoot]

https://hodgdonreloading.com/accurate/accurate-2520r

Max charge was 29.5 / 29.6 grains

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.

[LR1955]

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.

Join the club.

LR-55

[biodsl]

Glad you're okay.

[LRRPF52]

Can you post pictures of the case please?

[muvef]

https://hodgdonreloading.com/accurate/accurate-2520r

Max charge was 29.5 / 29.6 grains

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.

Nosler says 29.5 grains with their 120 gr BT.

Weird.

[lazyengineer]

Aannnnd another Lapua catastrophic case failure.

[lazyengineer]

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

[LRRPF52]

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.

[LRRPF52]

Aannnnd another Lapua catastrophic case failure.

[lazyengineer]

Been here 3 years, this is the 4th or 5th kaboom. The number of kaboom's/user/unit time is stunning. Common demoninator is lapua/starline.

[LRRPF52]

[DIANEB]

Hornady says 29.1 grains of A2520 is max...
Anything over 28.5 grains of A2520 my groups fall apart...

[LRRPF52]