C158 Bolts vs. MPI

[Doc Safari]

I read various sellers toutng C158 bolts as an "upgrade" versus standard milspec MPI bolts.

I would think no matter what material the bolt is made from, magnetic particle inspection and high pressure testing for flaws and cracks would be a necessary quality assurance step.

I think calling a C158 bolt an "upgrade" is just marketing and is not really an indicator that the bolt is GTG.

What say you?

[Pappabear]

I have never understood all the various materials. Therefore I just buy from reputable manufacturers because Im not smart enough. I also say this material or that material is like saying 100% cotton ( in some instances). And we know cotton can feel dramatically different from one to another.

Care to share the Mfg?

PB

[Doc Safari]

The last one I saw was PSA but I think there are others.

[mack7.62]

I though Carpenter 158 was the mil spec steel specified. MPI is a good thing but you do know that KAC believes that firing a high pressure round during testing shortens bolt life by up to 50%. They don't proof their bolts and warranty them for I believe 22,000 rounds.

[MegademiC]

I read various sellers toutng C158 bolts as an "upgrade" versus standard milspec MPI bolts.

I would think no matter what material the bolt is made from, magnetic particle inspection and high pressure testing for flaws and cracks would be a necessary quality assurance step.

I think calling a C158 bolt an "upgrade" is just marketing and is not really an indicator that the bolt is GTG.

What say you?

C158 is milspec. So is mpi testing iirc.

[tehpwnag3]

I think you are falling into the "match grade" trap with regard to mil-spec product descriptions.

The last one I saw was PSA but I think there are others.

[Todd.K]

C158 is spec.
NITRIDE IS NOT. Until proven otherwise I consider other materials and nitride to be cost cutting rather than engineering driven.

HP testing is a remnant of a different time for engineering and metallurgy. Like well before the M16 was designed.

[Doc Safari]

HP testing is a remnant of a different time for engineering and metallurgy. Like well before the M16 was designed.

Yet BCM marks their bolts HP for high-pressure testing. So what's the dealio?

[Wake27]

The actual mil-spec is Carpenter 158 (material) for the bolt tested with HP/proof round and then MPI. The last two are processes, not materials. Nitride is a coating and an alternative to phosphate and therefore also not a material that the bolt would be made up of.

The rumor mentioned above of KAC is what I’ve heard of centurion. Not sure which is true, or both, or neither, but it stands to reason that and extremely high pressure round would add stress and therefore shorten the lifespan. Typically I agree with PB and look more for the manufacturer than the materials and tests. Just because something was MPI’d, doesn’t mean that it actually passed to an acceptable standard, it just means they looked (at least that’s my understanding). If I’m going cheap, like PSA, then I’ll definitely go with their premium BCG which is supposed to be fully nil-spec to also include grade 8 fasteners and proper staking. My sample size of one seems to reflect that.

Yet BCM marks their bolts HP for high-pressure testing. So what's the dealio?

May be outdated but that’s still what the TDP calls for.

Sent from my iPhone using Tapatalk

[Doc Safari]

So C158 is nothing special, i.e., not a material "better than milspec?"

It's all hype. PSA is just proud that they do what everybody should do in the first place.