Former Grendel

[osage]

PPU brass/FGMM primer/BLC2 31gr/120grAmax/ 2.251 OAL. None of the preceding rounds had pressure signs. I pulled down the remainder to make sure of the powder charge. 31gr. The cam pin was bent, gouged about a 3/8 grove in my Vltor upper, knocked a strip of finish off the outside. Blew the magazine apart. At the end of the day I was shootin reloads so I bear responsibility. This was the 17th round of the morning. After gathering up my parts I went and checked out the target. Every bull looked like it was shot at with buckshot. So either the scope is also screwed, I forgot how to shoot overnight or something was going on.

[osage]

Can anyone clue me in on how to post pics ? Thanks

[LRS_Ranger]

I use photobucket and then link from there...

Curious to see what the assessment is on this one...

[bwaites]

Osage, PM sent.

Bill

[LR1955]

PPU brass/FGMM primer/BLC2 31gr/120grAmax/ 2.251 OAL. None of the preceding rounds had pressure signs. I pulled down the remainder to make sure of the powder charge. 31gr. The cam pin was bent, gouged about a 3/8 grove in my Vltor upper, knocked a strip of finish off the outside. Blew the magazine apart. At the end of the day I was shootin reloads so I bear responsibility. This was the 17th round of the morning. After gathering up my parts I went and checked out the target. Every bull looked like it was shot at with buckshot. So either the scope is also screwed, I forgot how to shoot overnight or something was going on.

OS:

So, are you saying you had an out of battery firing?

LR1955

[osage]

LR1955, yes. I went and pulled the target down too. I had loaded 3 rounds in the mag, there are 2 holes in the target. I had assumed it was the 2nd round that blew up but being as I could find all the pieces of the follower but not the loaded third round I am pretty sure the third round blew up while being chambered. Its the only thing I can come up with that makes sense.

[LR1955]

LR1955, yes. I went and pulled the target down too. I had loaded 3 rounds in the mag, there are 2 holes in the target. I had assumed it was the 2nd round that blew up but being as I could find all the pieces of the follower but not the loaded third round I am pretty sure the third round blew up while being chambered. Its the only thing I can come up with that makes sense.

Osage:

Yes, you had an out of battery firing.

I note you were using the 120 grain Hornady AMAX and the Federal Gold Medal Match primer.

I have never had a out of battery firing with the Federal GM primers in any rifle and I have shot many thousands of rounds of hand loaded ammo out of bolt and gas guns using Federal GM primers without any problems what so ever so I discount the primer itself.

When I seat primers, either using a progressive press or using a hand seater, I visually inspect the case to ensure the primer is seated just below the rim. A primer that protrudes from the brass is prone to going off when a bolt hits it on closure. If you do not have a procedure in place where you visually inspect every cartridge you load to ensure the primer is seated below the base of the rim, you should initiate one.

Finally, the 120 Amax bullet we have noted not to be ideal for the Grendel due to the ogive design. The ogive design is tangent and guys have said they had to seat the bullet so deeply into a Grendel case that the neck sometimes protrudes past where the shank and ogive meet. This is way deep but they had to because the Grendel chamber is cut very short. The 120 Amax is not a good choice for the Grendel as they end up having to jam it into the lands or seat it so deeply that it eats up powder space. Either way you are talking huge pressure spikes.

If you seated your 120 Amax bullets without paying attention to how close they were to the lands, after ten or fifteen firings enough crud will have built up in the chamber to give the conditions where the cartridge isn't going into battery enough to be safe.

Combine this poorly designed bullet for the Grendel plus the potential that you had a primer which wasn't seated deeply enough and add the intertial firing pin of the AR series of weapons and you have the ingredients for an out of battery firing.

Case closed.

LR1955

[osage]

Talked to Mr. Alexander this morning. Sending it all to him. Just to be clear, I bear full responsibility for what happened with my handloads. It in no way reflects on AA or any other company whose parts I used. bwaites, feel free to post the pics I emailed you. I still have not figured out how to do it.

[bwaites]

Here you go!

First the bolt with casehead attached:


Then the casehead itsself:


Then the casehead and follower:


Then the upper:

[bwaites]

Then the upper through the port:

[bwaites]

Osage,

Where is the rest of the case, still stuck in the barrel?

[pinzgauer]

Combine this poorly designed bullet for the Grendel plus the potential that you had a primer which wasn't seated deeply enough and add the intertial firing pin of the AR series of weapons and you have the ingredients for an out of battery firing.

Definitely looks like out of battery based on the way the case split. I agree on the 120 AMAX, just problems with the Grendel exactly as you described.

One question: I have read that a firing pin strike out of battery is not technically possible with the AR design as the pin is not long enough unless fully in battery with the bolt fully back in the carrier. Which can't occur out of battery.

My suspicion is you are right about a high primer, about the most likely cause for an out of battery firing.

[LR1955]

Definitely looks like out of battery based on the way the case split. I agree on the 120 AMAX, just problems with the Grendel exactly as you described.

One question: I have read that a firing pin strike out of battery is not technically possible with the AR design as the pin is not long enough unless fully in battery with the bolt fully back in the carrier. Which can't occur out of battery.

PG:

You are right. The inertial firing pin / bolt design themselves are intended to ensure such things do not happen and unless something is way out of spec with the firing pin or firing pin hole, they alone aren't the cause.

However, combine a functional firing pin / bolt assembly with a couple of more issues and the ingredients can combine to cause the out of battery firing. I am pretty convinced that the 120 AMAX bullets had to be seated in such a manner in order to feed and shoot that they were probably the baseline reason why it all happened. Most likely another ingredient was a primer not fully seated. However it could also be the one in 1M primer that was weak or sensitive for some reason and that, combined with it not being fully seated, combined with a firing pin on the edge of specs, ...... etc. You guys get the picture.

I would also view a high primer as far more possible if he used a progressive press or seated the primer on a regular press primer feed arm thing than if he seated the primer by hand.

I doubt it could be replicated with any predictability. The problem with out of battery firings is figuring out the cause.

LR1955

[osage]

Yes Bill the rest of the case is in the chamber and on its way to AA. Mr. Alexander wanted to see it and offered to inspect it and tell me if the barrel/barrel extension was ok to use. I prime with a hand primer, I clean the primer pocket, I weigh each powder charge and use a hand press to reload. I load for the Grendel the same way I do my SSG69 just 1 at a time. I spoke with Mr. Alexander at length yesterday and he seemed to think the 120gr Amax was likely the problem too. That being said it isnt Hornadys fault either, I should have done more research instead of just loading the 120Amax. It is the bullet my .308 prefers so I figured it was a good place to start. Live and learn. I was up front with both AA and Vltor and both still stood by their product even though I broke it.

[Darkop]

looks like case head separation. The primer is not flat at all. What kind of BCG? is it a shrouded firing pin BCG? Can you post a picture of the underside of the BCG?

Until that day,
Darkop