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Link Posted: 7/13/2009 4:31:22 AM EDT
Link Posted: 7/13/2009 4:54:23 AM EDT
Originally Posted By 103:
Originally Posted By EWP:
Originally Posted By suprshootr:
Originally Posted By EWP:
Originally Posted By dookie1481:
Originally Posted By DvlDog:
Originally Posted By lamarbrog:

Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.

CMMG claims shot peening, too. http://palmettostatearmory.com/434.php

BCM also claims shot peening. http://www.bravocompanyusa.com/BCM-AR15-Bolt-Assembly-MPI-p/bcm%20bolt%20assemly%20mp.htm



I wasnt aware of either of those. I wouldnt be terribly suprised if they are reselling LMT bolts anyway. Im not trying to start any crap but I find it terribly unlikely that both CMMG and BCM tooled up to make MPI and shotpeened bolts. Especially in the case of CMMG who based on my experience trying to source parts from them never seems to have anything in stock and after taking your money makes you wait until the next "batch comes in" (2yrs ago I waited 6 months on a barrel for a friends build) Plus if asked they play cloak and dagger about who makes their stuff. Until I see production line pictures from a CMMG or BCM owned factory I will continue to purchase Colt and LMT bolts (and some Youngs)



Paul has alluded to the fact that they source most of their parts, however, they still have to pass QC. You can get the cheap package from CMT and get batch tested bolts or pay more and get individually tested bolts.

Jay


You can buy CMT bolts that have been for sure MP tested and stamped for $50


Where?


CMT MP Bolts


The only option there is for "Standard."


The MPI ones sold out last week, but they were in stock for about a week.
Link Posted: 7/13/2009 5:19:33 AM EDT
[Last Edit: 7/13/2009 5:21:57 AM EDT by BR870]
Originally Posted By EWP:
Originally Posted By lamarbrog:

Originally Posted By EWP:
Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.


Fail Zero probably makes the best BCG, and yes they do all the testing Colt and LMT does and then some.

■Case Hardened, Shot Peened and MPI Bolt (Magnetic Particle Inspected)
■EXO Coated Bolt (40% more wear resistant than Chrome with a very Low Coefficient of Friction)
■Mil-Spec Gas Rings
■EXO Coated Carrier
■Chrome Lined Gas Key
■Gas Key Hardened to USGI Specifications
■Grade 8 Hardened Fasteners
■Blue Extractor Insert
■Mil-Spec Staked Gas Key
■MPI Tested Bolt

Uh oh.... This won't end well.


Blue, black, yellow, it doesn't matter. The insert is to make up for lack of a good enough spring anyway. Young's doesn't even put inserts in their extractor springs, plus just because it's black in some of the other companies bolts doesn't mean it's of the correct durometer anyway. I run the Tactical Springs spring with no insert or O-ring because it's a good enough spring it can handle the cycle demand put on it , so you don't need the extra junk in your bolt to begin with.

EWP


This is not true. Blue inserts are less rigid than black. Alot of people think they originally just switched colors to mark the spring change, but its more than that. Blue extractors yeild more easily. According to Paul at BCM, black have a Durometer rating of 80, while blue only have a durometer rating of 60.

(Sorry CJan_NH, had to use your pic)

Read this whole thread, and look for Paul at BCM's answers specifically.

http://www.ar15.com/forums/topic.html?b=3&f=118&t=408495&page=1

ETA: This wasn't totally directed at your EWP, so much as those who think a blue insert is just the same as a black...
Link Posted: 7/13/2009 6:15:19 AM EDT
Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.


BCM also shotpeens thier bolts. They are also made from 158 carpenter steel. They are ALL MPI as well. The majority of them are HPT as well.

LMT are all SP, HPT, MPI

Colt are all SP, HPT, MPI
Link Posted: 7/13/2009 6:19:06 AM EDT
Originally Posted By DvlDog:
Originally Posted By lamarbrog:

Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.

CMMG claims shot peening, too. http://palmettostatearmory.com/434.php

BCM also claims shot peening. http://www.bravocompanyusa.com/BCM-AR15-Bolt-Assembly-MPI-p/bcm%20bolt%20assemly%20mp.htm



I wasnt aware of either of those. I wouldnt be terribly suprised if they are reselling LMT bolts anyway. Im not trying to start any crap but I find it terribly unlikely that both CMMG and BCM tooled up to make MPI and shotpeened bolts. Especially in the case of CMMG who based on my experience trying to source parts from them never seems to have anything in stock and after taking your money makes you wait until the next "batch comes in" (2yrs ago I waited 6 months on a barrel for a friends build) Plus if asked they play cloak and dagger about who makes their stuff. Until I see production line pictures from a CMMG or BCM owned factory I will continue to purchase Colt and LMT bolts (and some Youngs)



BCM doesn't make thier own in house. They source them. But the source has to make them to BCM specs. So even if CMT is the contractor that doesn't mean CMTs own brand of bolt and BCMs are the same. The BCM is built to BCM specs and the CMT is build to CMT specs. BCM products have some of the highest QC in the business.
Link Posted: 7/13/2009 10:20:00 AM EDT
Originally Posted By CTbuilder1:
Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.


BCM also shotpeens thier bolts. They are also made from 158 carpenter steel. They are ALL MPI as well. The majority of them are HPT as well.

LMT are all SP, HPT, MPI

Colt are all SP, HPT, MPI


What is HPT?

How important is it to SP,HPT, and MPI a bolt and why?

Does anyone know if CMMG bolts are SP, HPT and MPI? Is CMMG bolt and BCG GTG?
Link Posted: 7/13/2009 10:27:52 AM EDT
SP= Shot Peened

HPT= High pressure test, just means they shot a proof load of 60,000 PSI in the gun, Big deal

MPI= Magnetic Partical Inspection, this is a type of inspection to look for cracks before or after the proof load is shot
Link Posted: 7/13/2009 10:34:42 AM EDT
Originally Posted By CTbuilder1:
The only thing different on the new LMT BCGs is the MIM Key. The bolt itself has not changed. At this point I would take either one but lean towards BCM because of their extreme commitment to quality.

I still would say Colt, BCM and LMT are the top BCGs.


This.
Link Posted: 7/13/2009 10:37:15 AM EDT
Originally Posted By BR870:
Originally Posted By EWP:
Originally Posted By lamarbrog:

Originally Posted By EWP:
Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.


Fail Zero probably makes the best BCG, and yes they do all the testing Colt and LMT does and then some.

■Case Hardened, Shot Peened and MPI Bolt (Magnetic Particle Inspected)
■EXO Coated Bolt (40% more wear resistant than Chrome with a very Low Coefficient of Friction)
■Mil-Spec Gas Rings
■EXO Coated Carrier
■Chrome Lined Gas Key
■Gas Key Hardened to USGI Specifications
■Grade 8 Hardened Fasteners
■Blue Extractor Insert
■Mil-Spec Staked Gas Key
■MPI Tested Bolt

Uh oh.... This won't end well.


Blue, black, yellow, it doesn't matter. The insert is to make up for lack of a good enough spring anyway. Young's doesn't even put inserts in their extractor springs, plus just because it's black in some of the other companies bolts doesn't mean it's of the correct durometer anyway. I run the Tactical Springs spring with no insert or O-ring because it's a good enough spring it can handle the cycle demand put on it , so you don't need the extra junk in your bolt to begin with.

EWP


This is not true. Blue inserts are less rigid than black. Alot of people think they originally just switched colors to mark the spring change, but its more than that. Blue extractors yeild more easily. According to Paul at BCM, black have a Durometer rating of 80, while blue only have a durometer rating of 60.

http://home.comcast.net/~cjan99999/Colt_Inserts2.JPG (Sorry CJan_NH, had to use your pic)

Read this whole thread, and look for Paul at BCM's answers specifically.

http://www.ar15.com/forums/topic.html?b=3&f=118&t=408495&page=1

ETA: This wasn't totally directed at your EWP, so much as those who think a blue insert is just the same as a black...


This is true but again the added durometer of the insert is to take the load off of the spring and all black inserts are not made to the correct durometer. If you run the GOOD 5 coil CS springs you dont need inserts or o-rings because the spring is good enough to handle the load and cycle demand put on the spring to begain with.

Does BMC or anyone else shot peen their extractor springs as well?


All our springs are constructed from Certified Chrome Silicon wirestock to withstand extreme heat and highly cyclic rate. The certification rating ensures a consistency in the parent material of 95%, which translates to repeatable consistency in performance & function. Certified Valve Quality Chrome Silicon wire is used in very high stress applications such as, NASCAR, Formula One, Moto GP & Pro stock racing motor valve springs. It is not uncommon in some of these applications for valve springs to see 15,000,000 compression cycles in one race. It is this extraordinary capability that made Chrome Silicon wire the obvious choice in our spring production vs. music wire used in OEM springs and by most aftermarket competitors. In addition, all of our Chrome Silicon springs are heat treated, stress relieved, and shot peened in separate post winding treatments. We also treat each spring with a proprietary, deep-penetrating, Re-Micronized (to .3 Micron particle size), inhibited, Molybdenum-Disulfide(MoS2) formulation to eliminate 90% of all mechanical wear on the spring. The combination of materials & processes result in a loss of no more than 5% in spring efficiency. We take our extractor springs one step further in the form of Cryogenic Processing. This computerized, ultra low temperature process (-320°F) increases the strength & wear life of the parent material through a change in microstructure resulting in less retained austenite and more uniformity. Why cryogenics for the extractor spring and not our other springs? Due to the size of the extractor spring, high stress cyclic rates and asymmetrical temperature exposure, premature wear and or shortened spring life can occur. Cryogenics effectively combats these issues giving the spring a very predictable & uniform performance within the operation of the weapon cycle. It is NOT recommended that a D-Fender™ ring be used when using our extractor springs. CRANE O-Rings may be used, but are not needed due to the strength and durability of the spring itself.
Link Posted: 7/13/2009 10:43:47 AM EDT
Originally Posted By Winn:
Originally Posted By lamarbrog:

Originally Posted By Winn:
Originally Posted By lamarbrog:

Originally Posted By darktide:

I'd go for the BCM now, just because of the untested MIM key... It makes me nervous... I DON'T LIKE CHANGE!



The OPs question pertains to BOLTS, not MIM keys on bolt carriers.



If you notice, later on he asked where to find a LMT or BCM bolt/BCG.

Many novices, and even some more experienced shootings, will refer to the BCG as the "bolt".

So, in this type of thread, it is best to answer in regards to the whole unit, unless specified otherwise.


No, it's not ... and reading is fundamental ...


Originally Posted By suprshootr:

Who produces a better bolt ?

I figured they are about the same quality but I’ve been reading some not so good stuff about LMT's new gas key.

Have they changed their bolt it all?

Thanks


Don't you have summer school to attend to, or something.



Can't we all just get along?


Link Posted: 7/13/2009 10:48:04 AM EDT
Originally Posted By EWP:
Does BMC or anyone else shot peen their extractor springs as well?


http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm%20extractor%20spring%20upgrade.htm

BCM starts with only the highest quality chrome silicon material, heat treats to stress relieve the product and shot peens to add increased strength.
Link Posted: 7/13/2009 11:57:11 AM EDT
Are CMT bolts SP, HPT, or MPI?
Link Posted: 7/13/2009 12:03:05 PM EDT
Originally Posted By suprshootr:
Are CMT bolts SP, HPT, or MPI?


Not all of them. They do not HPT and I have not heard of them shot peening. Some of them are MPI but they are batch tested which means that only one out of a certain number is tested.

Colt, LMT and BCM Test every single bolt that they produce. For example - If you purchase a Colt BCG, that very one you buy was HPT and MPI. On top of that it was constructed from carpenter steel and shotpeened.
Link Posted: 7/13/2009 3:02:52 PM EDT
the answer to the ORIGINAL question,,,buy either with full confidence... the one you can find,,,,
Link Posted: 7/13/2009 3:35:29 PM EDT
Originally Posted By EWP:
Originally Posted By BR870:
Originally Posted By EWP:
Originally Posted By lamarbrog:

Originally Posted By EWP:
Originally Posted By DvlDog:
To address the OPs original question, and speaking specifically of the bolt and not the carrier: I would by the LMT. To my knowledge only Colt and LMT shotpeen their bolts. Because of this I only buy Colt and LMT.

MPI, Shoot peened...whats not to love.


Fail Zero probably makes the best BCG, and yes they do all the testing Colt and LMT does and then some.

■Case Hardened, Shot Peened and MPI Bolt (Magnetic Particle Inspected)
■EXO Coated Bolt (40% more wear resistant than Chrome with a very Low Coefficient of Friction)
■Mil-Spec Gas Rings
■EXO Coated Carrier
■Chrome Lined Gas Key
■Gas Key Hardened to USGI Specifications
■Grade 8 Hardened Fasteners
■Blue Extractor Insert
■Mil-Spec Staked Gas Key
■MPI Tested Bolt

Uh oh.... This won't end well.


Blue, black, yellow, it doesn't matter. The insert is to make up for lack of a good enough spring anyway. Young's doesn't even put inserts in their extractor springs, plus just because it's black in some of the other companies bolts doesn't mean it's of the correct durometer anyway. I run the Tactical Springs spring with no insert or O-ring because it's a good enough spring it can handle the cycle demand put on it , so you don't need the extra junk in your bolt to begin with.

EWP


This is not true. Blue inserts are less rigid than black. Alot of people think they originally just switched colors to mark the spring change, but its more than that. Blue extractors yeild more easily. According to Paul at BCM, black have a Durometer rating of 80, while blue only have a durometer rating of 60.

http://home.comcast.net/~cjan99999/Colt_Inserts2.JPG (Sorry CJan_NH, had to use your pic)

Read this whole thread, and look for Paul at BCM's answers specifically.

http://www.ar15.com/forums/topic.html?b=3&f=118&t=408495&page=1

ETA: This wasn't totally directed at your EWP, so much as those who think a blue insert is just the same as a black...


This is true but again the added durometer of the insert is to take the load off of the spring and all black inserts are not made to the correct durometer. If you run the GOOD 5 coil CS springs you dont need inserts or o-rings because the spring is good enough to handle the load and cycle demand put on the spring to begain with.

Does BMC or anyone else shot peen their extractor springs as well?

<snip>



The wording is a little off, but the "meaning" is accurate ... not all black inserts are created equal.

Link Posted: 7/13/2009 3:45:38 PM EDT
I had 2 LMT's but replaced the MIM gas keys and sold both in favor of BCM's.
Link Posted: 7/13/2009 4:41:05 PM EDT
[Last Edit: 7/13/2009 4:44:39 PM EDT by Winn]
Originally Posted By BR870:

Well the LMT bolt does have the undercuts. Theoretically that should reduce the cracking stress on the lugs...



Can someone please explain (pics would be even better) the "who, what, where ..." of the undercuts on the LMT bolt ?

Link Posted: 7/13/2009 4:48:09 PM EDT
Originally Posted By Winn:
Originally Posted By BR870:

Well the LMT bolt does have the undercuts. Theoretically that should reduce the cracking stress on the lugs...



Can someone please explain (pics would be even better) the "who, what, where ..." of the undercuts on the LMT bolt ?



Link Posted: 7/13/2009 4:53:45 PM EDT
[Last Edit: 7/13/2009 4:55:11 PM EDT by Winn]

VERY Nice ...

Thanks.



Link Posted: 7/13/2009 4:56:10 PM EDT
Originally Posted By Winn:

VERY Nice ...

Thanks.





yep
Link Posted: 7/13/2009 5:15:18 PM EDT
Originally Posted By flyboy1788:
Originally Posted By Winn:

VERY Nice ...

Thanks.





yep


What exactly does this do?

Jay
Link Posted: 7/13/2009 5:16:11 PM EDT
LMT Enhanced BCG only way to fly without getting a Young Machine
Link Posted: 7/13/2009 5:18:17 PM EDT
Originally Posted By Sharpshooter:
LMT Enhanced BCG only way to fly without getting a Young Machine


Great for some guns, makes things worse in others.

Jay
Link Posted: 7/13/2009 5:19:13 PM EDT
[Last Edit: 7/16/2009 3:32:32 PM EDT by Winn]
Originally Posted By dookie1481:
Originally Posted By flyboy1788:
Originally Posted By Winn:

VERY Nice ...

Thanks.



yep

What exactly does this do?

Jay



Originally Posted By Winn:
Originally Posted By BR870:

Well the LMT bolt does have the undercuts. Theoretically that should reduce the cracking stress on the lugs...

<snip>


Link Posted: 7/13/2009 5:21:50 PM EDT
[Last Edit: 7/16/2009 3:35:01 PM EDT by Winn]
Originally Posted By dookie1481:
Originally Posted By Sharpshooter:

LMT Enhanced BCG only way to fly without getting a Young Machine


Great for some guns, makes things worse in others.

Jay


+ 1.

Link Posted: 7/13/2009 5:23:41 PM EDT
Originally Posted By EWP:
Blue, black, yellow, it doesn't matter. The insert is to make up for lack of a good enough spring anyway. Young's doesn't even put inserts in their extractor springs, plus just because it's black in some of the other companies bolts doesn't mean it's of the correct durometer anyway. I run the Tactical Springs spring with no insert or O-ring because it's a good enough spring it can handle the cycle demand put on it , so you don't need the extra junk in your bolt to begin with.

EWP


I only have a sample size of 2 but both of my YM NM BCG's had blue inserts. I use the BCM HD spring & black insert in all of mine regardless.

FWIW I've had 3 RRA BCG's all of which had black inserts but when compared to BCM black inserts, the RRA's were obviously a little softer.
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