MP marking on Bolt

oneyeopn · Nov 29, 2012

A while back we were having a discussion in the forum about the testing procedures that S&W does on the M&P15. Someone noticed that there is a stamp on all the bolts that says "MP". Someone else commented that they talked to the mothership and were told that the MP stands for Military and Police. Well I have found out that that is not true. MP is a standard marking on bolts that means Magnetic Particle Inspected, depending on the manufacturer of the Bolt there are a few different stampings but MP is one of the standard stampings meaning it was individually inspected. I do not at this time remember who sells the bolts to S&W but they are individually Mag. Part. inspected and then are stamped MP. Occasionally some weird info comes out of the Mothership and this was one of those times. Just had to clear this up. Just because S&W doesnt individually inspect them, why would they have to if they buy them from someone who does?

WardenRoss · Nov 29, 2012

Groovy info Grover!

Good to know! Thanks.

Stebo · Nov 29, 2012

Yes, I remember when that discussion took place. We had been told by an individual ( who shall remain nameless) as part of his usual S&W bashing, that M&P bolts were not MPI'd, later modifying that to batch tested only. We later learned that ALL M&P15 bolts were MPI'd, I think that info was turned up by Foxtrot. I have to admit that I knew MP, sometimes with a manufacturer's mark, stippled on the bolt indicated it had been tested. We took a survey and everyone who responded had that marking.

Thanks for clarifying that for everyone, Grover.

cyphertext · Nov 29, 2012

Rumor has it that the BCG is the semi auto LMT. Don't know if it is true, just what I have seen on the net.

Milky · Nov 29, 2012

I was watching a video on youtube where a gentleman pulled the BCG from his sport and his bolt was marked MP. I was excited so when I got the chance to inspect mine I was disappointed to find no MP markings on my bolt.

I'm not sure if this means that s&w went with another supplier on BCG or the original manufacture just didn't stamp it, or maybe they just inspected a number of bolts from a lot and a few lucky m&p 15 owners got the inspected BCG's. This is all speculation on my part, but I would have liked to have the piece of mind that the little MP stamp provides.

oneyeopn · Nov 29, 2012

Milky it is hard to see but it is on the side of the bolt, both of the sports here have it marked on it. I will post a pic, my older sport it is hard to see but it is there!
and its on the bolt, not the bolt carrier

Milky · Nov 29, 2012

oneyeopn said:
Milky it is hard to see but it is on the side of the bolt, both of the sports here have it marked on it. I will post a pic, my older sport it is hard to see but it is there!
and its on the bolt, not the bolt carrier

Not necessary to post a pic (iirc it is on the side right behind the bolt face opposite of the extractor) if I'm wrong then yeah maybe a pic will help.

I will double check after I get home from work in about an hour and a half, and make sure to wipe away any lube that is on it. It is very possible that the lube is covering it up especially if it isn't a deep stamp or hard to see.

Don't want to spread any fear or doubt about it so I will give it another look.

By the way, everyone on this site has been super helpful, and I don't see people bashing others for asking questions like I do on my states gun owner forum. I appreciate this forum, and respect the members for truly trying to help rather than trying to make themselves feel superior by putting others down.

rojodiablo · Nov 29, 2012

Milky said:
I was watching a video on youtube where a gentleman pulled the BCG from his sport and his bolt was marked MP. I was excited so when I got the chance to inspect mine I was disappointed to find no MP markings on my bolt.

I'm not sure if this means that s&w went with another supplier on BCG or the original manufacture just didn't stamp it, or maybe they just inspected a number of bolts from a lot and a few lucky m&p 15 owners got the inspected BCG's. This is all speculation on my part, but I would have liked to have the piece of mind that the little MP stamp provides.

The good news is that basically all the bolts from reputable manufacturers are forged from the same material. While it's nice to know that yes, the bolt was MPI, but then again, if you have sent 2000 rounds downrange and the bolt has had no issues...... then MPI or not, it's a good part.
Likely, when a company has such a production run as S&W had in the last 2 years, there would be some expected outsourcing. So long as the design criteria is met, and the proper materials are used, the extra steps of testing via chemical, x ray, or ultrasonic are just icing on the cake.

In the case of who exactly is making parts for whom; companies like S&W, Colt, etc are BIG shops. And, they have requirements their suppliers must meet. Usually, a tiny shop can not qualify as a supplier, simply for lack of production ability. Yet a small shop might make some custom stuff; hot rod triggers for special rifles, special barrels that are low production items, and higher ticket items.
Likely, Stag, Remington/ Fredom group or whatever it is called will likely be filling in some gaps. (They have DPMS and Bushmaster- a pretty big operation.) S&W was making barrels for another manufacturer for a while this year, I suppose they still do plenty of subcontract work/ recipriocity with other mfg.

Milky · Nov 29, 2012

oneyeopn said:
Milky it is hard to see but it is on the side of the bolt, both of the sports here have it marked on it. I will post a pic, my older sport it is hard to see but it is there!
and its on the bolt, not the bolt carrier

I happily stand corrected!!!

I wiped the lube off the side of my bolt to reveal a very lightly stamped "MP".

Sorry for adding to any confusion on the matter.

Mustang5L5 · Nov 30, 2012

Just checked my Sport I bought last year. Bolt does have MP on it

Sent from my iPhone 4S using Tapatalk

WardenRoss · Nov 30, 2012

Hey! You forgot to post a PICTURE!

C4IGrant · Nov 30, 2012

oneyeopn said:
A while back we were having a discussion in the forum about the testing procedures that S&W does on the M&P15. Someone noticed that there is a stamp on all the bolts that says "MP". Someone else commented that they talked to the mothership and were told that the MP stands for Military and Police. Well I have found out that that is not true. MP is a standard marking on bolts that means Magnetic Particle Inspected, depending on the manufacturer of the Bolt there are a few different stampings but MP is one of the standard stampings meaning it was individually inspected. I do not at this time remember who sells the bolts to S&W but they are individually Mag. Part. inspected and then are stamped MP. Occasionally some weird info comes out of the Mothership and this was one of those times. Just had to clear this up. Just because S&W doesnt individually inspect them, why would they have to if they buy them from someone who does?

Ya, S&W's CS knows nothing about they products they sell (in regards to technical things like this).

Little history for the folks, S&W orginally bought BCG's from CMT. Then, after a falling out, they went to LMT. Due to lack of availability, they moved to another OEM manufacturer (that does put out quality). They remain with this company to this day.

My guess is that at some point S&W will start to make BCG's in house.

C4

C4IGrant · Nov 30, 2012

Stebo said:
Yes, I remember when that discussion took place. We had been told by an individual ( who shall remain nameless) as part of his usual S&W bashing, that M&P bolts were not MPI'd, later modifying that to batch tested only. We later learned that ALL M&P15 bolts were MPI'd, I think that info was turned up by Foxtrot. I have to admit that I knew MP, sometimes with a manufacturer's mark, stippled on the bolt indicated it had been tested. We took a survey and everyone who responded had that marking.

Thanks for clarifying that for everyone, Grover.

LOL, its ok to use my name. S&W has a varied history on BCG's. Some were NEVER HPT/MPI and others were. For instance, when they got BCG's from CMT, they were not HPT/MPI. When they went to LMT, they were. Their current source does have the capability of HPT/MPI. I have asked them (S&W) if they are having EVERY bolt HPT'd and MPI'd.

C4

oneyeopn · Nov 30, 2012

C4IGrant said:
Ya, I just checked some SPORT rifles and they did not have a marked bolt. I have to wonder if they didn't go to a cheaper bolt OR they are the same Bolt's they always used, but stopped marking them (as they no longer MP test).

C4

If you look above he retracted his statement when he found his bolt MP tested. As I did more searching I found that the MP stands for Magnetic particle and Pressure testing. It seems to be an industry standard especially for Military and LEO markets. It would make no sense to buy bolts from one supplier for the Mil and Pol markets and another for the consumer market when the same bolt would prove to be a quality product in both. S&W is known for quality products over their long history of firearms manufacture and I would be very amazed to see them change now. Especially since they are the second highest manufacture/sales firearms company.

C4IGrant · Nov 30, 2012

oneyeopn said:
If you look above he retracted his statement when he found his bolt MP tested. As I did more searching I found that the MP stands for Magnetic particle and Pressure testing. It seems to be an industry standard especially for Military and LEO markets. It would make no sense to buy bolts from one supplier for the Mil and Pol markets and another for the consumer market when the same bolt would prove to be a quality product in both. S&W is known for quality products over their long history of firearms manufacture and I would be very amazed to see them change now. Especially since they are the second highest manufacture/sales firearms company.

Ya I saw that and then went back and double checked the gun I had looked at and it was marked. It was so light (coupled with crappy lighting) that I missed it (my bad).

MP does NOT also mean HPT. It never has and is why many companies like BCM mark their bolt: HP MP.

As someone that buys bolt and BCG's from several OEM manufacturers, you can get bolt's with NO testing, with just MPI and with both HPT and MPI (every unit or in batches). Just depends on what you are willing to pay for.

C4

cyphertext · Nov 30, 2012

I tend to agree with Grant on this one....with parts availability and demand, it's a crapshoot where S&W is getting their parts. We don't know for certain. Remember the marketing exec that stated all uppers and lowers are forged in house when they introduced the Sport, yet many of us have other forge markings on our uppers?

If it was for certain known that every bcg was tested, surely they would list it in their spec sheet.

But really, I am at the point now of who cares...shoot it and shoot it some more until it breaks. When it does break, I'll call up Grant and get replacement parts, and at that time, I can buy a BCG that is known to be fully tested.

C4IGrant · Nov 30, 2012

cyphertext said:
I tend to agree with Grant on this one....with parts availability and demand, it's a crapshoot where S&W is getting their parts. We don't know for certain. Remember the marketing exec that stated all uppers and lowers are forged in house when they introduced the Sport, yet many of us have other forge markings on our uppers?

If it was for certain known that every bcg was tested, surely they would list it in their spec sheet.

But really, I am at the point now of who cares...shoot it and shoot it some more until it breaks. When it does break, I'll call up Grant and get replacement parts, and at that time, I can buy a BCG that is known to be fully tested.

As my friend Paul (owner of BCM) always tells me; "If you go through the HUGE PITA to HPT and MPI, wouldn't you scream it from the roof tops? It is a big selling point and to not market it would be stupid."

http://www.bravocompanymfg.com/accessories/bolt_carrier_group.php

C4

Stebo · Nov 30, 2012

C4IGrant said:
As my friend Paul (owner of BCM) always tells me; "If you go through the HUGE PITA to HPT and MPI, wouldn't you scream it from the roof tops? It is a big selling point and to not market it would be stupid."

BCM® Rifle Company

Now that is special. Your good friend tells us it's all about "marketing".

Funny thing is, I just looked on the Colt website, and cannot find any screaming about MPI/HPT.

So far, in the past few weeks, you've told us;
- S&W does NOT MPI their bolts
- well, maybe they only batch test
- well, probably they lie and mark them MP but they aren't really.

C4IGrant · Nov 30, 2012

Stebo said:
Now that is special. Your good friend tells us it's all about "marketing".

Funny thing is, I just looked on the Colt website, and cannot find any screaming about MPI/HPT.

Colt doesn't have too as the TDP demands it so there is no other way for them to do it.

If you are trying to show the consumer that you spend a lot of extra time/money on your products, you for sure better market it! Because if you don't you are simply wasting your time and money.

So far, in the past few weeks, you've told us;
- S&W does NOT MPI their bolts
- well, maybe they only batch test
- well, probably they lie and mark them MP but they aren't really.

If you look at the listing of all companies that I listed (where S&W has purchased BCG's from) I am 100% right. At various times, they have used BCG's that had zero testing done to them.

I do think they buy their bolts with MPI (NOW). The question is, was HPT done prior and was it done to EVERY bolt or was it done in batch. We don't know and my question directly to S&W came back with neutral answer (they don't know either as they don't do it in house).

So IMHO, there are some assumptions being made here and quite frankly, no one knows.

For me, I would want to see paper work like I posted here before I would say for certain: Be an informed consumer! - M4Carbine.net Forums

C4

oneyeopn · Nov 30, 2012

Yep I have been to M4Carbines...and have been told that I bought a piece of junk, that unless I buy the dancing pony or one of the boutique manufactures I have wasted my money. When I go to a forum and find it populated with "gun snobs" I dont stick around long. I am not in a financial situation to drop $1400 on up on what they consider an entry level rifle. But I can take a sport and do everything that I want with it and do it well. I now have enough rounds through my Sport that if anything was made cheaply it would have broken. I have shot enough test loads and yes some of them overpressure (not many) but when I was not getting the performance loading to .223rem data levels, I knew there was something different. Now that Hornady has released the 5.56x45 loading data my most accurate loads are listed, but nothing has broken. So what they would say at M4Carbine, or AR15 and some of the other "tactical rifle" sites has no relevance on my life or in my world because my S&W far surpasses what the advertised performance limits are.
Grant, sometimes I agree with you, sometimes not but I would never try to say you dont have the right to. In the other forums that I have visited, it has been said they are getting better, I could not get a question answered, they were too busy berating my choice of rifle.
this has been my experience and I am sure not everyone has had this experience. But I have!

MP marking on Bolt

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