Just happened.

Specs.  Wilson Combat upper/lower set.  Christensen Arms 6.5 Grendel barrel.  Jp bcq and Young bolt.  I have about 40-50 rounds through this rifle with a JP bolt.  This time I was setting up a new scope and going to do a bolt test with 3 bolts.  The jp, a Young manufacturing, and the monster 6.5 bolt.

Factory Hornady Eld 6.5 Grendel Ammo.

Young Manufacturing bolt brand new failed after two rounds.
Bolt ordered Jan 6, 2018,  Invoice# 3759.

Jp bolt in originally.   Sighted in, shot the following group at 100 yds.  Switched to the young bolt.  Shot one, shot number two more right than it should be and then noticed the carnage.  So failure occurred on the second shot.




Other half of brass is in the chamber.  Gun ejected the half brass and lodged the next round in the roof.

Thoughts opinions on this.

Another pic.  Added left brass shot with JP bolt for the last 40-50 rounds.


Moar.  Same orientation as above 3 shots.



Lug pic.  Young MF proof.


Case head.


Bolt up close, should be able to zoom in good.




Carrier cam pin area damage.



Upper receiver damage. Raised bulge where that damage is.  Carrier binds in receiver.


Other half of brass recovered.  



Fired brass with JP bolt 1.510"
1st brass fired with Young bolt 1.509"
2nd brass fired with Young bolt 1.557".  Failure round.

Just for comparison.  Using Hornady comparator.
Fired brass specs for these bolts:
JP 1.2135"
Young 1.2140"
Larue Factory 6.5 Grendel 1.2145"

Right now I believe the bolt had begun failing after the first shot as brass is normal with normal primer strike. Second shot primer is nearly pierced and bolt begins collapsing causing the excessive expansion and tearing case in half.  Also, there was no gasses from the failure introduced into the receiver.  The bolt held long enough for the case to seal in the chamber, so I got lucky on that part.

3/3/18  Bolt failure, Young Manufacturing 6.5 Grendel
3/3/18  Contacted Young via email, tagged this post in email.  Asked that they look it over and get back to me.
3/5/18. Made a follow up call to Young Manufacturing to verify email was received.  Received but had not been looked at according to Young.
3/9/18. Zero contact with Young since.  No reply to email, nothing.

Thanks

Bill

What kind of ammo?

I would say bolt failure.

I am dumb about kabooms.   In for thoughts.

freedom munitions?

Factory Hornady Eld

Overcharged. Or bump stock.

IMHO, that's not an overpressure failure, because the brass is intact all around the head.

That is a bolt material failure, most likely from improper material or most likely, improper heat treating.  That bolt shattered.  The case separation is likely a side effect from the bolt giving way.

(Unless the 6.5 grendel does not fail the same way 5.56 does, and their bolts are inherently weak by design.... im not as well versed in 6.5g - but this is highly unlikely or bolt failure like this would be very commonplace.  I have read there is more bolt thrust, and from looking at Young's bolt description they redesigned their bolt at some point saying "no more broken bolts")

Headspace is my guess

Barrel lugs look okay still, one has a slight scuff.  Not sure how to get the brass out of the chamber.

That's impressive in a scary way.
Is the case head intact?
if so it's not ammo and I'd guess a meturalogical fault / failure.

Beat by FAL

There are two different sized bolts for the Grendel.

Sure that one was the proper size?

Edit

That brass to the left was shot right before the failure

It was more fun before the edit

What does headspace have to do with bolt failure?  Or on a technical level - how could headspace be related?  I'm curious.

Interesting.  Never seen a bolt shatter like that.  Beats me.  Maybe hydrogen embrittlement?

I have no real idea. My guess is an improperly made bolt.

After I read this post I had to look away, close my eyes, and concentrate to remember how to spell metallurgical. For almost a full minute, I was genuinely unable to do so. I wasn't even sure about meteorological. It was very disorienting.

Bolt failure

I'd go with bolt defect as well, btw. I've never seen a 6.5G bolt up close, so I don't know if it's inherently weaker.

Possibly the coating on the Bolt created a bad head space.

Gotta be a bad bolt, never seen one blow like that

Agreed

What do the fored primers look like?

Any cratering?

Never seen a bolt kaboom before. Are any of those pieces the lugs?

What would the bolt look like if it fired without being locked?

I am trying to link the neck of the brass separating with the broken bolt but I cannot.

Is the barrel nut tight?

So us the primer strikes for both rounds.

ETA - Sorry, I see the pic of the primer strikes.

There was an explosion, I'd say gunpowder was involved.

Looks brittle AF.  Do they heat treat bolts after final machining or before.  I have trouble believing that metal that brittle wouldn't be noticed in the manufacturing process.

https://www.rainierarms.com/young-mfg-chrome-6-5-grendel-bolt/

Tag.

They over heated it grinding and lost the heat treatment

Bolt looks like pot metal.  Barrel nut torqued to 50 ft/lbs.  Those small pieces or are last several are the lugs.

Yeah well that shit disintegrated.

This.  6.5G has a .136 Bolt face recess, and .264 LRB has a .125 Bolt face recess.  This is also known a 6.5G Type I and Type II.

Using a Type I (.264 LRB) barrel with a Type 2 Bolt will have excessive head space.

My AK has never done that

Brother I kept trying and just let autospell do it. I knew it didn't look right but I'm too tired to care.

All the surface grinding I ever did in our machine shop was done under coolant, and very small metal removal at a time.  The parts never got warm.  Wouldn't bolt grinding follow the same principles?

You guys see the ‘smiley’ (‘C’ indentation) on the truncated brass?

Any ideas?

Can we get a better couple closeups of the failed case head?  To really see if there was ejector flow, head flattening, and primer flow.

Case head swipe.

Over charged.

I thought that too.  I'm not sure why everyone else is talking embrittlement, head, and the forecasting of metal falling from the sky (nickmemphis)

Bad bolt heat treat or material.

If that case head shows evidence of ejector flow of the brass into the ejector, then I'd tend to agree.... and after understanding that the 6.5G already suffers from bolt thrust issues with hot loads, I'd switch my vote to pressure.

That raised semicircle on the case head of the failed case looks like flow of brass into the ejector channel. Sign of overpressure

But usually you see it in combination with a flattened primer.

Flattened primer
Flattened primer with cratering around firing pin strike
Flattened primer with cratering and flow into ejector channel.

Hydrogen embrittlement or improper heat treat notice the extractor survived though bent. Primer shows no over pressure, was head space checked  after bolt switch?

Edit: Looking at new pics Combo bad heat treat and improper head space. Somehow slipped through the Q.C.

Looks brittle the way the bolt came apart.

You can try to find one of these in 6.5G.
https://www.brownells.com/gunsmith-tools-supplies/handgun-tools/stuck-case-removers/broken-shell-extractor-prod23311.aspx

Last person I know with this issue, could not extract with this setup (in .308) , and wound up using a tap and die set to grab the case, and a wood dowel to pound it out.

This.

No idea.
Push a brass chamber brush in from the ass-end and give it a sharp tug to remove what's left of the case.

No clue, I don't bother with  any of the Grendel cartridges.

As for the stuck case portion, run a oversized bore brush past it then pull it back out.

What happened is you bought a 6.5 Grendel. Be smart and don't make that mistake again.

Check out the DPMS G2 with a 6.5 Creedmoor barrel.