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Old 12-11-2013, 07:06 PM
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Originally Posted by luke_a View Post

Did you know that Carpenter makes all three materials mentioned in this thread? Guess which one they recommend for AR15/M16/M4 bolts? It's not 9310.
Fine. We'll agree to disagree. I'm not going to argue over which type of "strength" is stronger.

But I do know which type of steel costs more and who pockets the cash. Just follow the money and you'll know why c158 is still the "recommended" steel...by the very same.
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Old 12-11-2013, 07:16 PM
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I know they tested a new CARRIER (currently made of 8620, not 9310 or c158). I'm not aware of any recent tests to the bolt itself...but I'd love to see them if you can link to them.

Right now JP is the most respected, high-end bolt on the market. You'd pay more for the bolt itself than Kev is planning to spend on an entire BCG. It is made with 9310 and here's their rationale:

http://www.jprifles.com/1.4.7_bc.php

All carriers are 8620 as far as I know, I've never seen one that wasn't. 8620 is the Mil-spec for carriers.

That material description about the enhanced is marketing hype. Yes their design is improved, the machining is better than most mil-spec bolts, so it might last longer. I don't think anybody would dispute that. LMT also makes an enhanced bolt with a similar design and made from A-100.

That's where the facts end and the hype begins.

Life expectancy of a mil-spec bolt is 6,000 rounds? Seriously? I guess my LMT bolt must be completely destroyed with the 15k rounds it has seen. I bet Unobatanium has put a crap load of rounds through his mil-spec bolts too. Pat Rogers students put 13k rounds through the BCM filthy 14 rifle without any cleaning before the extractor spring failed, it went to 16k rounds before the bolt broke. This is with no cleaning at all, and being shot only in carbine classes which is the most stress any of our rifles will ever see outside of a combat situation. I have a 8620 Bushmaster bolt that has seen at least 12k rounds(bought it used) and the bolt is still in great shape. JP is being less than truthful in their statements.

And to say that they are the most respected on the market isn't accurate. Which market are you referring too? The uneducated buyers? The 3 gun comp shooters? Professional operators? Enthusiasts? They might have the 3 gun market, I'll give you that, but they definitely don't have the professional operator market.
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Old 12-11-2013, 07:21 PM
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Originally Posted by Skyjump136 View Post
Fine. We'll agree to disagree. I'm not going to argue over which type of "strength" is stronger.

But I do know which type of steel costs more and who pockets the cash. Just follow the money and you'll know why C158 is still the "recommended" steel...by the very same.
I follow the the advice of professional operators and carbine class instructors who have seen everything fail at one point or another. When they see 9310 bolts fail on a regular basis, and they see Eotech optics fail on a regular basis, and bushmaster rifles fall apart on the course, they speak and I listen.

If Carpenter was in it for the money, they'd be pushing A-100, it's 3 times more expensive for the end buyer than C-158 and easier to manufacture.
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Old 12-11-2013, 10:11 PM
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Just got a reply from wilson combat,

Quote:
The entire assembly is 9310. Bolt and Carrier.
So would you buy the BCG?
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Old 12-11-2013, 10:20 PM
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Originally Posted by Skyjump136 View Post
I know they tested a new CARRIER (currently made of 8620, not 9310 or c158). I'm not aware of any recent tests to the bolt itself...but I'd love to see them if you can link to them.

Right now JP is the most respected, high-end bolt on the market. You'd pay more for the bolt itself than Kev is planning to spend on an entire BCG. It is made with 9310 and here's their rationale:

http://www.jprifles.com/1.4.7_bc.php
9310 looks better on paper, but in practice, C158 is the superior material for this application. I will not pretend to be a metallurgist, but I will defer to Bill Alexander on the subject. Who is that guy?
http://www.alexanderarms.com/company-information

Here is what he has to say:
Quote:
Bolts are becoming a pet subject!

It is always interesting to consider the bolt within the context of its application. To do so will draw not only on stress analysis, but also on fatigue theory and metalurgy. This will quickly move the solution beyond the simple question of which steel is best, for the best steel if applied out of context will not perform adequately.

So for simple illustration let us assume that the steels are applied well, before discussing the differences.

Carpenter 158 is without doubt an excellent material for the production of M16 bolts. The material is clean with negliable elements in the make up that are detrimental to the fatigue life. It can operate happily within the confines of the enviromental requirements imposed by the application and has a very low deformation of the parts as they run through heat treatment. The down side to the material is that it was designed to heat treat in large sections so the thin bolt material will respond somewhat voilently. Again not an immediate problem if the heat treatment is absolutely perfect but within the confines of a production enviroment it will throw problems.

By comparison AISI 9310 will on first inspection also make an adequate bolt material. It has several alloy elements that promote a better structure and in the correct heat treatment will provide a slightly higher toughness than Carpenter 158 which is benificial to the fatigue life. Corrosion resistance is slightly higher but as with C158 it should not be applied without some form of surface protection. Thin section response to quenching is somewaht less than C158 which makes it better suited to the manufacture of bolts. However by comparison to Carpenter 158, AISI 9310 has several elements present in its composition that are detrimental to fatigue while not being evident in the physical properties.

It has become evident from the industry that a number of manufacturers have jumped upon the AISI 9310 wagon in order to claim better performance. While in theory an AISI 9310 bolt may perform better I would not typically select this material specification. There are a wide number of superior alloys available without resorting to the nickel based maraging alloys which are expensive, difficult to machine and extremely temperamental in behaviour. The steel industry has advanced since the specification of Carpenter 158 but the basic premises for the selection remain even if the menu has now expanded.

Bill Alexander
http://www.m4carbine.net/showthread....228#post387228
Quote:
AISI 9310 has a number of drawbacks in use for the bolt of an M16 type rifle , not least of which is that in this application the fatigue life is lower than Carpenter 158 as a result of certain tramp elements commonly found in the alloy. This is not to imply that Carpenter 158 is the pinnacle for this application but that AISI 9310 is not optimum either. Both have drawbacks and advantages.

The rush to produce AISI 9310 bolts without an understanding of the problems will create not stronger bolts but those with a wider spread of service life.

A well executed 8620 bolt will outperform a higher alloy if it is not well made and heat treated.

Bill Alexander
http://www.m4carbine.net/showthread....397#post387397
I cannot think of anyone with more qualification than Bill Alexander who has commented on such.


Here is hte PiP. It is for a "Bolt carrier assembly".

That means bolt AND carrier, of course, and when have you ever heard of a carrier taking a dump? I think the winner was likely selected because of the bolt, cam-pin track, etc.

https://www.fbo.gov/?s=opportunity&m...=core&_cview=1

Quote:
PHASE II: Exploring Improvements
PM SW completed its best value M4 bolt and bolt carrier assembly competition in April 2012, though the competition was scheduled to conclude in summer 2013. More than six months of testing and evaluation determined that none of the 11 competing designs met the overall requirements outlined in the solicitation. The M4’s current bolt and bolt carrier assembly outperforms the competing designs in the areas of reliability, durability, and high-temp/low-temp tests. The Army saved nearly $2 million as a result of the early completion of the competition.

http://peosoldier.armylive.dodlive.m...am-pip-update/
So ask yourself, now...even IF you somehow have rationalized 9310 or some other alloy as a superior MATERIAL...which it's not (excluding A-100), how do you rationalize implementation, when we can clearly see that 11 other companies, the list of which is no-longer public, but which included LWRC and LMT as interested vendors, failed to better the mil-spec in reliability and durability?

It's not all about material, sometimes. Many times, it has to do with material for the JOB. C158 bolts are the right material, for the job, unless you want to go with A-100, and good luck finding it.

Realistically, you can expect a bolt to die at 3-5K rounds on a hard-run suppressed full-auto SBR. 6-10K rounds on a very hard run M4. 10-15K rounds on a hard-run M4 mid-length. 15K+ on a rifle gas system. (minimum life-expectancies given abusive firing-schedules.)

Replacement bolts cost $60-80 for a mil-spec offering.

It's a total non-issue. Consider it part of PM.
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Old 12-11-2013, 10:25 PM
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Originally Posted by kev View Post
Just got a reply from wilson combat,



So would you buy the BCG?
No, I would personally stick with a known quantity. I fail to see any advantage that it might offer, and can think of many unknowns that it introduces into the equation. I would stick with mil-spec on BCG's.
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Old 12-11-2013, 10:26 PM
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Originally Posted by luke_a View Post
I follow the the advice of professional operators and carbine class instructors who have seen everything fail at one point or another. When they see 9310 bolts fail on a regular basis, and they see Eotech optics fail on a regular basis, and bushmaster rifles fall apart on the course, they speak and I listen.

If Carpenter was in it for the money, they'd be pushing A-100, it's 3 times more expensive for the end buyer than C-158 and easier to manufacture.
I believe A-100 is what KAC is using on their bolts, but the comparison is not valid because of their different lug geometry and cam-pin dimensions.


I freely admit to trading rifles before I reach the wear-out point. However, I have never seen anyone break a bolt at any carbine course I have gone to. Most everyone used quality mil-spec offerings, and fired 1000-1500 rounds. Rifles ranged from nearly new, to 15K+ rounds old.

I will say that Kyle Lamb uses an Eotech, as do the active duty Delta instructors I know. The Eotech has certain advantages, and the new EXPS series solves almost all of the old durability issues.

I have seen Kyle Lamb and one of his instructors (Active Delta) using JP rifles. I have also seen an LA state trooper pull out a .308 JP precision rifle. They are making inroads into the "professional" market. Kyle Lamb and his group's usage of JP products, however, could likely be traced to swag secondary to his consulting for them, though. This is very possible, and I would take any usage of any product with a grain of salt. LAV is on Aimpoint's payroll, and he talks them up. He even provided some input to the T1, which is probably part of why he is so attached to it. He used to talk Daniel Defense up, a LOT! But when they let him go, he immediately cease to mention them at any point, unless forced to by the discussion at hand, and then he is cool/factual/neutral. He now heartily recommends BCM at every point he can.

Take industry professionals brand preferences with a grain of salt unless they actively use the item in life/death circumstances.
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Old 12-11-2013, 10:37 PM
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What do y'all think about aim surplus's C158 bolts? Are they quality? I see they have Spikes Tac. for about $120... I'd be inclined to go with one of those. I see Aim is offering their "own" NiB 9310 BCG's for a very decent price... if you can find them in stock. I just have a hard time gambling on something as critical as a BCG so I'd be hard pressed to go with something other than my tried and true BCM BCG's. I hear really good things about Spikes BCG's - and guns in general, from people that shoot WAY more than I do... I'd be inclined to just stick with what is tried and true. A 9310 NiB BCG is really tempting though...
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Old 12-11-2013, 10:41 PM
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What do y'all think about aim surplus's C158 bolts? Are they quality? I see they have Spikes Tac. for about $120... I'd be inclined to go with one of those. I see Aim is offering their "own" NiB 9310 BCG's for a very decent price... if you can find them in stock. I just have a hard time gambling on something as critical as a BCG so I'd be hard pressed to go with something other than my tried and true BCM BCG's. I hear really good things about Spikes BCG's - and guns in general, from people that shoot WAY more than I do... I'd be inclined to just stick with what is tried and true. A 9310 NiB BCG is really tempting though...

While I am impressed with everything I have recieved from PSA, I am worried at how they are getting the prices so low... I see they are now branding a "PTAC" kit that is supposed to be budget type parts. I would be inclined to just spend the extra $40 and get something like the Spikes BCG, of a little bit more and get one from BCM.

AIM - http://www.aimsurplus.com/catalog.as...Carrier+Groups

I guess moral of the story; how are they getting the cost down? That raise concern IMO.
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Old 12-11-2013, 10:44 PM
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No, I would personally stick with a known quantity. I fail to see any advantage that it might offer, and can think of many unknowns that it introduces into the equation. I would stick with mil-spec on BCG's.
I think that is a good idea.

Probably going to stick with a 158 bolt.
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Old 12-12-2013, 01:50 AM
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Originally Posted by CPL_BS_88 View Post
What do y'all think about aim surplus's C158 bolts? Are they quality? I see they have Spikes Tac. for about $120... I'd be inclined to go with one of those. I see Aim is offering their "own" NiB 9310 BCG's for a very decent price... if you can find them in stock. I just have a hard time gambling on something as critical as a BCG so I'd be hard pressed to go with something other than my tried and true BCM BCG's. I hear really good things about Spikes BCG's - and guns in general, from people that shoot WAY more than I do... I'd be inclined to just stick with what is tried and true. A 9310 NiB BCG is really tempting though...
Of course AIM doesn't make their own bolts, but there really is very little way of knowing that they are quality. However, if they are C158 and HPT/MPI, they are likely made by the same contractors making them for others, and I would presume that they are okay. However, the best way to know you are getting a quality bolt is to buy one from Colt, BCM, LMT, Daniel Defense, etc.

A good lubricant will give much more performance increase than will a wondercoating. Get a good BCG, nevermind the plating/coating. AAC won't even use coated bolts because of hydrogen embrittlement potential.
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Old 12-28-2013, 11:56 PM
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The only reason this is controversial is due to misinformation from smaller gun companies who cannot afford to buy a minimum quantity batch of C158. 9310 is easy to get and not bad - but certainly not as good as C158 for AR bolts. Call up Carpenter and ask - they make both.

Quote:
Originally Posted by DRT4life
I have never seen or had a BCG failure in 30+ years of shooting M16/AR15's....
Short barrels with suppressors will make them start to crack in 5000-6000 rounds and generally fail at around 10000. 20 inch barrels could go for 25000 rounds.

With 7.62x39mm ARs in a short barrel with a suppressor and full auto, I was breaking them in 200-300 rounds.
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Old 10-18-2019, 09:57 AM
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https://faxonfirearms.com/blog/why-9...ar15-m16-bolt/
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Old 10-20-2019, 04:42 PM
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I like Faxon. As inexpensive as those are I might grab a few for spares and one to use as a beater.

Wish you had not made me go to their website. Want to spend money now...
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Old 10-21-2019, 01:43 PM
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"9310 is not MIL-SPEC, it's better than MIL-SPEC"

Last week Faxon announced the release of their GUNNER series of Modern Sporting Rifle bolt carrier groups. Its been a pleasure working on the carriers and we are thrilled to have them released to our customers to rave reviews. We were able to create something never done before: A steel carrier, keeping forward assists, full-auto compatible, and less than 6.5 ounces!

One of the questions we have been getting is why we opt to not follow the "Mil-Spec" for our bolts, specifically why we are not using Carpenter 158 steel for the bolts?

The answer is simple: "Mil-Spec" is just the minimum requirement and metallurgical technology has caught up to design of the AR-15 since its creation.

The reason for Carpenter 158 as the "Mil-Spec" is rooted in history when the AR-15, chambered for the lower pressure .223 Remington round was upgraded to the higher pressure 5.56 NATO loads. The original material selection for the bolt was found to have inadequate service life. The military went searching for better material, constrained by the size of the bolt. Carpenter Technologies' 158 blend of steel was selected as it provided adequate strength and wear characteristics. It has been the "Mil-Spec" since.

Since the creation of Carpenter 158, the metals industry has continued to innovate, creating new blends of steels. 9310 is a AISI standard grade of tool steel that makes it about ~7% stronger than "mil-spec" Carpenter 158 steels, when appropriately treated. Its commonly used in the aerospace industry where toughness, impact strength, and solid wear characteristics are required.

From the base material, we took what we liked from the "Mil-Spec" and continued development. Our 9310 bolts are still magnetic particle inspected (ensures consistent material), shot-peened (surface strength), and heat-treated (for shock, abrasion, and wear) like the Mil-Spec. With 9310, the heat-treat is critical and all steps are completed with full certifications.

From there, Faxon opted for nitrided bolts instead of manganese phosphate finihs. "Nitriding" or nitrocarburization is applied for us via Quench, Polish, Quench method. The process imbunes nitrogen into the steel hardening the surface, reduces friction, and increases corrosion resistance. We use the same process on all of our barrels. This creates a slicker, more corrosion resistant bolt that is simulatneoulsy harder to resist wear.

As such, the combination of 9310, correct treatment methods, and QPQ create a better bolt; one that exceeds "Mil-Spec".

9310 Carpenter 158 MIL-SPEC C158 Bolt AR-
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Old 10-21-2019, 07:30 PM
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From there, Faxon opted for nitrided bolts instead of manganese phosphate finihs. "Nitriding" or nitrocarburization is applied for us via Quench, Polish, Quench method. The process imbunes nitrogen into the steel hardening the surface, reduces friction, and increases corrosion resistance. -
I read this part and then looked at the price before deciding to try a few soon.

Want to see if the nitrocarburization stuff is half what they claim it to be. Currently have no AR parts treated this way but DO have a set of brake rotors done with this process. Have been beating the hell out of them and they still don't show hardly any wear. Have also noticed they don't seem to mind heat at all as a 'stock' set would have been noticeably warped by now.
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Old 10-22-2019, 08:45 AM
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Originally Posted by luke_a View Post
All carriers are 8620 as far as I know, I've never seen one that wasn't. 8620 is the Mil-spec for carriers.

That material description about the enhanced is marketing hype. Yes their design is improved, the machining is better than most mil-spec bolts, so it might last longer. I don't think anybody would dispute that. LMT also makes an enhanced bolt with a similar design and made from A-100.

That's where the facts end and the hype begins.

Life expectancy of a mil-spec bolt is 6,000 rounds? Seriously? I guess my LMT bolt must be completely destroyed with the 15k rounds it has seen. I bet Unobatanium has put a crap load of rounds through his mil-spec bolts too. Pat Rogers students put 13k rounds through the BCM filthy 14 rifle without any cleaning before the extractor spring failed, it went to 16k rounds before the bolt broke. This is with no cleaning at all, and being shot only in carbine classes which is the most stress any of our rifles will ever see outside of a combat situation. I have a 8620 Bushmaster bolt that has seen at least 12k rounds(bought it used) and the bolt is still in great shape. JP is being less than truthful in their statements.

And to say that they are the most respected on the market isn't accurate. Which market are you referring too? The uneducated buyers? The 3 gun comp shooters? Professional operators? Enthusiasts? They might have the 3 gun market, I'll give you that, but they definitely don't have the professional operator market.
Understand that military life-cycle numbers are based on full-auto fire being in the mix. I shot Filthy 14 at two different classes, and considered Pat as one of my professional mentors. He knew more about the M16/AR15 platform than anyone else I have ever met. He was a big fan of plain Jane bolts/bcg's. As he said, they are one of many wear items. If you actually shoot, parts will break, regardless of what they are made of. Keep spares on-hand. Problem solved.

I don't shoot full auto, and I have never had a BCM, Colt, or SOLGW bolt fail before the 16k mark. Many have exceeded 30k. They usually outlast my barrels. It's been about a year, but last time I talked to anyone had Knights, they still have never had a bolt breakage reported on one of their SR16 bolts.
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Old 10-24-2019, 05:36 AM
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Wow...holy thread resurrection. Since 2013, many things have developed. I am personally aware of multiple 9310 QPQ bolts which have been tested to over 20K rounds of M855A1 without failure. The added lubricity of the QPQ treated metal/on/metal action within the barrel extension reduces the axial loading of the bolt lugs, which is a primary failure point in higher round-count bolts.With proper heat and QPQ treat, as well as adherence to dimensional call-outs, I have zero issues trusting a 9310 QPQ bolt/carrier group. In addition, a QPQ BCG will slightly increase cyclic rate vs. phosphate. I recommend Azimuth as a supplier for a proper QPQ BCG.
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