Bolt Failure today..

[bp7178]

hydrogen embrittlement

My first thought when I saw NP3.

[Ryno12]

It's that silly Froglube shit that you use.





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[DBR]

Hydrogen embrittlement is a potential issue with electroless nickle plating. There are several different types of E-nickle with different phosphate content. There are post plating bake-out protocols to reduce the embrittlement risk and they are fairly strict regarding how soon after plating and how they must be applied.

Personally, I would not use a plated bolt no matter who made it. I do not see the risk/reward.

[Failure2Stop]

With a 16" barreled semi-automatic sans suppressor, should we expect a much longer bolt life?

It's extremely hard to predict without testing all of the variables.
I try to replace mine at around 5k, and I have not lost a lug yet from my 16" guns.

[T2C]

It's extremely hard to predict without testing all of the variables.
I try to replace mine at around 5k, and I have not lost a lug yet from my 16" guns.

Thanks for the response. I don't have any experience working on short barrel carbines with suppressors.

I personally don't own anything with a barrel shorter than 16" and I don't have a suppressor. I have run a few bolts up to 10K without any failures and replaced a few others around the 7K-8K mark when they started to look a little worn. The carbine bolts seem to take a bit more of a beating than the bolts on my rifles. In every case, I replace the bolt when I replace the barrel.

Our work rifles did not see nearly the rounds my personal equipment does, so I haven't seen many bolt failures.

Keep the information coming guys. This is good stuff.

[JoshNC]

Interesting topic and discussion. I have an LMT 10.5 upper with Colt BCG that has probably close to 7k rounds on it, nearly all suppressed and fullauto. I will be retiring the bolt ASAP; I think I'm on borrowed time with this.

It is also interesting that some bolt failures are like yours, Mark, while others literally detonate the upper and blow the guts of the mag through the floorplate.

F2S, were the M4a1 bolt failures similar to mark's or were they more catastrophic?

[markm]

Did it lock up again after the 40 additional rounds, or did you just decide to stop shooting at that point?

Just decided to wrap it up for the day. Not sure how many rounds, if any, were fired with the next lug broken. Actually... now that I think of it, the second lug break is still pretty clean metal. The first break is blackened from shooting the gun some more.

[djegators]

Are there any tells you look for to replace a bolt, or are most of you just replacing based on round count? Also, how big is the concern of using a new bolt on a used a barrel?

[markm]

Mark how wet did you keep the bolt? Wondering if that had anything to do with it.

This bolt was well lubed and fired in my Syrac 11.5 tuned to run like a pussy cat. The carrier is what I believe to be a colt. It's an old Slick Side but there's no "C" on it. Not sure if they stamped anything on the carriers back then.

[scooter22]

Are there any tells you look for to replace a bolt, or are most of you just replacing based on round count? Also, how big is the concern of using a new bolt on a used a barrel?

There's no concern regarding a new bolt on used barrel. Hence, replacing the bolt @ 5k.

I have read that it is not advisable to run a used bolt on a new barrel, but I have no experience...