Grendel Kaboom w/ Young's MFG Bolt

[Kswhitetails]

I believe the additional headspace created when the bolt failed and began to back away from the chamber under pressure could cause that. Hard to take any pressure sign seriously from the brass when the boat looks like it does in this case.

[Djgrendel]

Visual inspection of a case head after a separation like that is not going to solve anything. Especially when the lugs that lock the chamber are no longer lugs. Out of curiosity, you should measure case wall thickness at the separation. On each half. Cut cases 1 and 2 at the same location. Measure their wall thickness as well. Once that bolt went, it went for good. I bet the #3 case is paper thin at the separation. Bolt failure is the culprit.

[bj139]

Out of an interest in safety, I posted about this on another website. They had issue with the ar15.com link and deleted it.
They said it was an overpressure round and that every manufacturer makes bad parts from time to time so Young is not to blame.
I don't know.

[Bill3508]

The brass of the failed round...looks like the imprint of the extractor or ejector hole on the back of it. Also looks like a flat primer. If not overpressure (hot round, etc), what would cause that?

Sean

Actually the primer isn't flat at all if you zoom in. Their is an ejector mark I guess from once the bolt failed.

[Bill3508]

Visual inspection of a case head after a separation like that is not going to solve anything. Especially when the lugs that lock the chamber are no longer lugs. Out of curiosity, you should measure case wall thickness at the separation. On each half. Cut cases 1 and 2 at the same location. Measure their wall thickness as well. Once that bolt went, it went for good. I bet the #3 case is paper thin at the separation. Bolt failure is the culprit.

Cartridge length of the first Young round as well as the jp round is posted at the bottom of op post. 2nd Young round is substantially longer due to the bolt failure.

[Bill3508]

Out of an interest in safety, I posted about this on another website. They had issue with the ar15.com link and deleted it.
They said it was an overpressure round and that every manufacturer makes bad parts from time to time so Young is not to blame.
I don't know.

LoL. Young apparently doesn't care either so.

[6.5_fanatic]

Actually the primer isn't flat at all if you zoom in. Their is an ejector mark I guess from once the bolt failed.

The primer isn't flat but it is cratered.

[Bill3508]

The primer isn't flat but it is cratered.

Yep, that's why I think the bolt started failing on the first round. First round fired on this bolt is perfect in all aspects. Second round, primer is nearly pierced and bolt collapses.

On another note why does it delete my post if I try to edit a spelling error?

[Dcommoncents]

On another note why does it delete my post if I try to edit a spelling error?

It does that to me on my phone, but not computer. No idea why.

[6.5_fanatic]

A cratered primer could also mean a hot load. I've had a few loads that would crater but they never would flatten the primer.

[98Z]

A cratered primer could also mean a hot load. I've had a few loads that would crater but they never would flatten the primer.

Or, a firing pin hole that's too large, in the bolt face. That is common on the DPMS GII in .308 Win. Craters primers like a champ, but doesn't flatten them. I've seen one account so far where a GII customer complained about it, and DPMS sent them a new bolt with a smaller firing pin hole, and a redesigned firing pin. Don't know if they fixed it on the current production rifles, or they're only sending the new bolt to customers that have a gripe with it. They are aware of it, though, if they've made steps to correct it...

[Bill3508]

The bolt is going to be sent off to have a full testing on the metal and hardness. Should be interesting seeing as the bolt looks like Chinese pot metal. Well proceed from there once I get that info back.

[Kswhitetails]

You might keep some pieces to test for yourself. Just a thought.

[NugginFutz]

+1

Years ago, my father was up a Sears aluminum extension ladder, pruning one of our trees. Mom was underneath, steadying it. Without warning, the thing collapsed and my father fell, landing on my mom, ladder and all.

Sears first insinuated they had overloaded it, and tried to deny any liability. Once it was determined that dad was a good 100 lbs less than the ladder's rating, they then wanted it back "to test". No soap. My dad permitted them to send someone out to remove a sample from the bent portion to analyze, but the ladder stayed.

Long story short, Sears paid the settlement (hospital bills, damages and, least of all, a new ladder!). We can't say with certainty that they would have absconded and left my parents high and dry, but by keeping control over the evidence, they were assured there would be no funny business.

[LRRPF52]

Out of an interest in safety, I posted about this on another website. They had issue with the ar15.com link and deleted it.
They said it was an overpressure round and that every manufacturer makes bad parts from time to time so Young is not to blame.
I don't know.

So far, I haven't seen any indicators that there was an overpressured cartridge.

The extractor being in position is the first clue, as stated before. The lack of soot around the case, and lack of signs that the gas path flowed back into the action are other huge clues.

Someone with an extremely limited experience with firearms would make that kind of conclusion, ignoring obvious signs of extremely unusual metal fatigue.

A Grendel bolt will take excessive pressure with more than a few rounds also. Even if one were firing loads that exceeded SAAMI MAP by 5-10ksi, you wouldn't see immediate failure. You would have to run a substantial round count to get one of the lugs to crack adjacent to the extractor pocket, and then you would normally only see one or two lugs shear, if at all.

Within 2-3 firings, if a bolt fails like yours did, where every single lug broke off AND cracked spirally around the cam pin hole, you know you're dealing with a failed metallurgy part.

I'm not knocking Young's, because I have stuff from them that has been great. This part just should have never made it through a TQM program. Heat treat is too long or too hot or both.

[bldsmith]

Looking at the grain structure of that bolt from the fractured section there is probably a couple possibilities . It was run at too high a temp before the quench or was overheated and not properly annealed before heat treat. The grain should be nice and smooth, more like broken glass, not like a gravel road.

Not heat annealed properly.


After proper annealing.


Not annealing/normalizing will cause brittle components.

[Bill3508]

I'm more pissed that Young won't even reply and isn't even interested in determining if their bolt was the faulty. Given that I worked on my rifle yesterday cleaning up the gouge in the carrier cam pin area and making sure the rest of it was okay. Also smoothed out the bump in the receiver and got the carrier moving freely again. Setup a new bolt and I'm getting good lug contact all around so seems like the barrel lugs are good to go.
Ran a dozen rounds through it checking the brass after each one and everything looks good. Headspace looks good and normal brass growth. Will have to watch to see if the cam pin wears any extra where the carrier was smooth and keep an eye out on the receiver area, but both areas are non critical so hopefully it won't be an issue. Won't ever be using Young's products again as they don't even care enough to reply.

Thanks folks.

[Klem]

I'm more pissed that Young won't even reply and isn't even interested in determining if their bolt was the faulty. Given that I worked on my rifle yesterday cleaning up the gouge in the carrier cam pin area and making sure the rest of it was okay. Also smoothed out the bump in the receiver and got the carrier moving freely again. Setup a new bolt and I'm getting good lug contact all around so seems like the barrel lugs are good to go.
Ran a dozen rounds through it checking the brass after each one and everything looks good. Headspace looks good and normal brass growth. Will have to watch to see if the cam pin wears any extra where the carrier was smooth and keep an eye out on the receiver area, but both areas are non critical so hopefully it won't be an issue. Won't ever be using Young's products again as they don't even care enough to reply.

Thanks folks.

I would ring them - This is their number 623-915-3889 (Someone will answer).

[Bill3508]

I would ring them - This is their number 623-915-3889 (Someone will answer).

I'm waiting for the hardness and data report on their bolt. Once I have that it will be posted and further contact will be made.

[Kswhitetails]

Any update here, Bill? Interested to see what was determined, and if any blame is to be laid. Sometimes bad things go bad, I'm still glad to read that you're okay and that in the long run this will likely be just an event along your timeline rather than a branch in it. Best of luck.