MPI - Any Way To Tell?

[tpelle]

Is there any way to tell if a bolt has been magnetic particle inspected? Are they routinely marked in any way?

[markm]

No way to tell that I know of.

They're routinely marked MPI. The lack of markings is meaningless.

[mlosi762]

No way to tell that I know of.

They're routinely marked MPI. The lack of markings is meaningless.

Not necessarily true. Most reputable manufactures will stamp MPI if the bolt is in fact, MPI. many also stamp an "SP" (BCM for example) to indicate that is shot peened as well. Depending on who makes it, I wouldn't use a bolt that did not have those markings.

[markm]

Often times bolts are MPI'd even if the customer doesn't want it. There was a company that flat out said.... we MPI all of them... too much hastle to sort off Non MPI bolts.

I too will run Colt or BCM bolts... but I have one bolt group in a recreational AR that is of unknown pedigree.

[TangoSauce]

I think they're generally marked.

[BobinLaConner]

If you are worried or doubt it was done, just take it to a local Nondestructive test lab and they can run a quick magnetic particle test for you. On stainless parts, you will have to have them do a penetrant test. Magnetic Particle will show discontinuities that are open to (or very close to) the surface but if they are subsurface they may be hard or nearly impossible to find. It is a great test for machined parts and locating cracks or linear defects.

[djthemac]

My dd is not marked

[Stryker medic]

Advantages/difference between MPI stamped vs. SP stamped?

[RowlandP]

Here's my Sig M400 and Colt bolts. The Sig is not marked and the Colt is.

http://i1125.photobucket.com/albums/l590/RowlandParks/My%20Guns/010-4.jpg

[BobinLaConner]

Just for a sample at what a crack found with magnetic particle looks like under ultraviolet light. This is a small retainer ring that showed pretty extensive cracks,that were not visible at all to the naked eye under normal light. The test itself only takes a few minutes.

http://i410.photobucket.com/albums/pp190/BobinCovington/th_magneticparticlecracks.jpg?t=1334535626

[FortTom]

I use a Spikes NiB bolt. It is shot peened and marked HPT/MPI.
FT

[tpelle]

FortTom, just curious, but are located in Fort Thomas in Campbell County? If so, we're neighbors almost, as I live in Camp Springs.

[markm]

I use a Spikes NiB bolt. It is shot peened and marked HPT/MPI.
FT

My buddy who is an Armorer and a Mod on another forum saw Spikes testing Certs.... They were jookie at best.

[Mamba6]

Advantages/difference between MPI stamped vs. SP stamped?

SP represents shot peening, a type of manufacturing process to create residual stresses in a metal to increase the strength of the material. Basically, its shooting ceramic, glass, or steel balls at a material, which act like sucessive ball-peen hammers. Its not really a test, more of an indicator that the strength of the bolt is greater.


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[FortTom]

I know lot's of armorer's, and have known many during my 20 year career in the military. Don't know where your buddy gets his "certs" info, but these are being sold to and installed in weapons used by multiple special operations units, including Navy, Army, Marine, British Royal Marines, and numerous other governmental agencies, of whose identities are not available to the public. Not sure what "jookie" means, but your "armorer" buddy sounds pretty "jookie" to me. Also, the Marines are purchasing these to send to Afhanistan, because they an be run 1500 or so rounds completely dry. As a matter of fact, very little lube is recommended, because of the super hard non-porus finsigh will sling most of it off anyway. I use them, I can clean them with a piece of T-Shirt and some gun scrubber (no scraping), I can "scrape" the carbon "build up" with my thumnail. During my years in the military, I would have stole one of these, if I had to, if I could have had one. As a desert warfare specialist, I would have loved to had the ability of these bolts to run in that fine powdery dust, not sand, that causes the real problems, especiallly with "wet" phosphorus finished standard bolt. Not trying to be argumentative here, but I've been shooting the M16/AR/M4 since I joined the military in 1975, and still doing them today, so a "buddy who is a MOD" at another site doesn't impress me at all, as onmiscient. I'll rely on my own firsthand knowledge, this (QC) info is freely available from Spikes if you ask nicely. I also make my decision on what works and doesn't with my own testing. Sure, I'll go to a forum and get some input about a product before I decide on plunking down a couple of Benjimans on an unknown, the AR is constantly changing, and new products come out every day, so I don't try to pretend that I know everything, I learn more all the time. Spikes NiB bolts are about $60 higher than the otther's NiB's built mostly by R.Runn, at $250 retail (around $210 acutal price which I pay for them.) There's a reason for that. The fanatical QC that Spikes puts into their Nickel Boron bolts, which by the way, are actually M16 bolts ( a little heavier). They also run cooler, and smoother than most of my previous standard phosphorous bolts. So whatever "jookie" means, I'll stick with my "jookie" spec'd bolts, as they are the best I've ever ran since 1975..

Thanks for the Heads Up...though.

J.

[markm]

Don't know where your buddy gets his "certs" info

Spikes gave it to him.

I don't have a dog in the fight... but I wouldn't take anything made by Spikes. I mean.. that stupid buffer they make is indication enough that they're a goofball operation.

There's no need to with companies like BCM, DD, and COLT very competetively priced.

[FortTom]

No need to have a dog in a fight. I'm not fighting the issue. I'm just telling you what I've experienced with 2 of them (NiB) BCU's, and other's also. Can't speak to their buffers or anything else "Spikes", because I don't have experience with any of their other products.
And I won't speak to a company or an issue, that I know nothing about, from firsthand personal experience. And I'm not trying to be confrontational about it. If I came off that way, chalk it up to poor written communication skills, on my part.

My only problem is, and I'm not accusing you of this, but I'm always hearing about something that someone who knows someone else, that heard it from a cousin, whose barber's stepson, mentioned to an in-law kind of thing. I'm actually using them, (the BCU's), and they've exceeded all expectations.

I have to disagree that BCM, DD, and Colt, and other's make infallible products. At least in one case. I once bought a Colt National Match AR, and it was the absolutely worst functioning AR, I ever owned. Luckily, I had a great friend who is not only an armorer, but a formally educated gunsmith. I refused to sell it, broken, and after we finally got it running like it should, I then sold it.

My latest build, or should I say assembly, is based on an LMT Lower and (Stripped) upper. One of the finest AR's I've ever owned. Functioned perfectly on the first shot, and the last. This friday, I'm going to the range, expect to put another 500 rounds down range, and expect no problems at all.

One thing, if you would or can do me a favor. If I PM you my address, do you think you can get copies of the data from Spikes? I'd really like to see it. Not doubting what your friend has is valid, but I'm a degreed engineer, with quite a bit of experience in metallurgy.
If something should go wrong, based on the Nickel Boron coating, and their spec sheets don't pan out, I'd like to personally contact them. 1st, as a line of defense, with raw data, and second, if their data and certifications is faulty, I'd like to know, why they'd be stupid enough to make it available, and 2nd, why is the military accepting them, and sending them in harm's way? That would sort of tick me off...

Thanks,
FT.

[BobinLaConner]

I'm not in any part of any heated discussion, only offering my input being a certified Nondestructive Inspector (certified in Magnetic particle, Ultrasonic, Penetrant and X-ray), so back on the MPI subject...remember that MPI is only a method of eliminating the rejected parts that contain indications (cracks or defects shown in the test). It does nothing to "improve" the characteristics. That would be up to the metallurgical make up and what qualities the designer intended. And cracks can still happen after using the parts from fatigue, misuse or poor metallurgical properties.

From what I have seen (and I have inspected firearm parts as well as aerospace parts), the parts are machined and then sent out for inspection (sometimes it is done in house). Most times the parts are sent out to a specialty vendor for shot peening, heat treating or coatings too. So certs could be printed on oil stained paper towels, but if they reference that a spec was followed and it is a reputable company, my gut tells me they had a valid process. I guess my point is that these vendors are pretty good at what they do and any of the reputable coatings or process providers have to meet quality spec requirements that mandate traceability or proof of how the process is performing.
My feeling is that MPI is a great test to start with an acceptable part, but don't look at it as "my barrel was stamped MPI'd so it will never fail". It would be a good idea to have any critical parts inspected periodically, (some race car steering components are done frequently through the life of the component to check for cracks that might develop during use). Cost is very low and you could probably have several parts done at once for the minimum shop order price . I would have quoted $250 to do 50 bolts just for an example. Worst case, buy some penetrant at a welding shop and learn how to use it. Also inspecting with your eyes and a flashlight every time you take things apart is a good thing too.
Hope that helps, I am happy to answer any technical questions on MPI if anyone has one.

[FortTom]

Thanks, very informative and pretty much sum's up a long subject in a couple of sentences. As an retired engineer, I've been involved in a little non-destructive testing (primarily aerospace parts manufacturing) and some bearing races while working for SKF. Although not my primary job, we were often in the loop, and most actual testing was done by highly trained technicians, in the field of NDT. My greatest concern in this thread, was people want to know how to tell if their bolt has received this test or that test, without actually knowing the importance or non-importance, or even having a fundemental understanding of these processes, and what they reveal to the tester. I think you summed it up very well.

FT.

[BobinLaConner]

hope it helps a little anyway...I don't want to diminish what some of the companies are doing when they promote MPI'd parts. It likely means they have a robust quality control system in place that seeks to improve the process, correct problems methodically and does not allow defective parts to get out to the market. That reduces the chances of things breaking right there, so that is a great thing. I applaud those companies for building in high quality on a such an important piece of gear that we count on with our life. Then if the owner of the gun takes the next step and does his own visual inspection at regular intervals during cleaning sessions, well that just helps the odds as well and is just good practice too.
If it were me, I would try to buy a gun with the barrel and bolt already MPI inspected. If I was worried in any way or had a "high mileage" part I might drop by a local test lab and ask how much they would charge to do the inspection. If you don't need the certs and traceability (since you are not reselling it) you might even be able to talk someone into trading a case of beer to do the MPI. Ask if you can watch, it is pretty interesting to see.

Stay safe and good shooting

[cz777]

ok now for the hair ball from hell ...i seen chine made ar parts floating around the gun shows and else where ...it looks good BUT i dont trust it so watch your step and dont smear us makers so hard ....everybody can let a lemon out the door ,it happens !!

[markm]

Yeah... I don't even go to gun shows anymore. Buy from reputable dealers online. Avoid the back page/ebay gamble.