View Full Version : AR15 Performance Super Bolt
How much stronger is the AR15 Performance Super Bolt compared to a standard bolt? I'm about to order parts to overhaul a couple of my department's full auto SBR's and since I'm replacing the bolts anyway the extra cost isn't a huge deal. I'm just trying to determine if they are really that much stronger. I'm also considering them for my patrol rifle and a couple .223 based wildcats I have that are a bit harder on bolts than standard .223. In my case, however, my rifles are due for new bolts so I'm not sure it's worth doing until they are ready for new stuff.
GermanSynergy
11-01-10, 12:18
What brand of carbines do you guys have? Just curious.
I've found BCM bolt/carriers to be excellent in several builds.
http://www.bravocompanyusa.com/BCM-AR15-Bolt-Assembly-MPI-p/bcm%20bolt%20assemly%20mp.htm
The two SWAT guns I'm going to be servicing are DPMS select fire 11.5" SBR's while the rest of the department rifles are DRMO Colt M16A1's. As for privately owned guns that guys buy to carry on duty we have a mix. Our policty doesn't dictate manufacturer and is open enough that someone could buy a Mini-14 if they really wanted to, though nobody has tried.
If I buy a standard bolt I will go with a high quality one like a BCM. I was just curious what guys have found using the AR15 Performance bolts. They appear to offer a very durable bolt and I'm all for durability and was hoping for some first hand experience to see if the premium price was worth it.
Heavy Metal
11-01-10, 13:19
http://www.ar15performance.com/inc/sdetail/336
This is what he is discussing. I must admit, this part intrigues me.
Heavy Metal
11-01-10, 13:20
As to the M16A1s?
The above would be overkill. I would run the original military bolt as long as you are on the original barrel.
The carbines may benefit by the superbolt.
Thanks for the link to the SB, as I really had no idea what he was talking about. The SB does indeed look interesting, but as far as I can tell there isn't much of a track record to see how the product performs in the long run. For as duty weapon, I would stick with a standard bolt, such as the BCM you mentioned. The duty weapon isn't a good choice for testing of a new item.
Someone correct me if I'm wrong, but isn't 9310 a grade BELOW 158 Carpenter?
I thought that bolt materials, in order from best to worst were:
158 Carpenter
9310
8620
I'm not up on my metallurgy but the JP high performance bolt is also 9310 and claims to be significantly stronger than mil-spec. Claims a service life of 60,000 rounds IIRC.
AFAICT:
9310 is inferior in strenght to carpenter 158.
9310 is easier to source in smaller quantities, and cheaper.
I would just go the BCM, DD, or LMT route, stronger steel, less expensive; they are of the highest quality.
https://www.m4carbine.net/showthread.php?t=30091&highlight=9310&page=2
Skip out on the "high Performance" bolt. You can just about get 2 bolts for every 1 of those you buy.
I'm not up on my metallurgy but the JP high performance bolt is also 9310 and claims to be significantly stronger than mil-spec. Claims a service life of 60,000 rounds IIRC.
I can claim a lot of shit, too. That doesn't mean it's the truth. Stick with what works, Carpenter 158. Buy BCM BCGs for those DPMS rifles, leave the Colts alone until they break.
After reviewing comments in the linked thread, I don't feel worthy to even post here.
After reviewing comments in the linked thread, I don't feel worthy to even post here.
Dont worry, this happens all the time to me.
I can claim a lot of shit, too. That doesn't mean it's the truth. Stick with what works, Carpenter 158. Buy BCM BCGs for those DPMS rifles, leave the Colts alone until they break.
I agree that they are just "claims" and not to be trusted. That's why I asked the question.
As for waiting for the Colt bolts to break, I'm not a fan of that idea. Bolts have a service life and can break at the most inopportune times...
AFAICT:
9310 is inferior in strenght to carpenter 158.
9310 is easier to source in smaller quantities, and cheaper.
I would just go the BCM, DD, or LMT route, stronger steel, less expensive; they are of the highest quality.
https://www.m4carbine.net/showthread.php?t=30091&highlight=9310&page=2
Skip out on the "high Performance" bolt. You can just about get 2 bolts for every 1 of those you buy.
Thanks for the link. Good reading and alot of info. I'd still like to see a heads up test for a true comparison but for now we'll stick with standard bolts.
So this Super Bolt has potentially better geometry, yet is made from inferior steel. One step forward, one step back.
Better geometry, potentially inferior steel. Unless someone gets 30 normal USGI bolts, 30 'enhanced' bolts, 30 bolts using traditional geometry but 9130, and 30 bolts using traditional materials but new geometry, and shoots the living piss out of all of them in an equal and systematic fashion, we'll never really know for sure.
-B
Ned Christiansen
11-02-10, 23:26
I think maybe the most important thing here is that the body is larger around the cam pin hole. I've been trying to get commercial bolt manufacturers to do that for a couple years. They are so thin there -- about .097-- that the 17% increase is huge. It's kinda like in engines-- the quickest way to more horselpower is more cubic inches. Well here, 17% more steel is a big deal. They didn't do it exactly the way I envisioned it but it would be every bit as effective, strength-wise. I need to try one of these out.
Tagging this one. Sounds very interesting.
There's always the LMT Enhanced and the LWRC Advanced; the read on the LWRC is especially interesting.
I haven't shot either of mine enough to come anywhere near their service lives.
Better geometry, potentially inferior steel. Unless someone gets 30 normal USGI bolts, 30 'enhanced' bolts, 30 bolts using traditional geometry but 9130, and 30 bolts using traditional materials but new geometry, and shoots the living piss out of all of them in an equal and systematic fashion, we'll never really know for sure.
-B
I would be very interested in this test. The enhanced bolts do tickle the impulse buyer in me; but I need more info on them to spend that much money when I can get a bolt for 1/2 price that is a known performer.
I would think that 2 bolts would outlast even a "high Performance" bolt meant for high round count, not sure though?
The SB does indeed look interesting, but as far as I can tell there isn't much of a track record to see how the product performs in the long run. For as duty weapon, I would stick with a standard bolt, such as the BCM you mentioned. The duty weapon isn't a good choice for testing of a new item.
Amen to that.
BufordTJustice
12-02-11, 16:06
I think maybe the most important thing here is that the body is larger around the cam pin hole. I've been trying to get commercial bolt manufacturers to do that for a couple years. They are so thin there -- about .097-- that the 17% increase is huge. It's kinda like in engines-- the quickest way to more horselpower is more cubic inches. Well here, 17% more steel is a big deal. They didn't do it exactly the way I envisioned it but it would be every bit as effective, strength-wise. I need to try one of these out.
I'm sorry for the necropost, but...well...I'm not really sorry.
Ned, Any updates on the use of this superbolt from ar15 performance?
I have a ARP bolt on my 6.8 aprox 1k rds on it.
So far so good!
For a 5.56 duty gun, I would chose Colt/BCM parts
C158 is very hard to get in small lots, and 9310 is a substitute. 9310 is not quite as good as C158 for a bolt, but, it is not a bad material.
Bolts are weak spots on ARs, and I am very open to the concept of improving on the 50 year old mil spec design - the KAC E3 bolt seems clearly better.
Even Colt has advanced bolt and carrier designs which outperform the mil spec - and they submit them to things like the IC competition and M4 product improvement - but they just cannot put them into the existing contracts.
There is no doubt that better than mil spec bolts are real, but this particular one was probably not tested as much as a company like KAC would do simply due to the cost of 200,000 rounds of ammo.
Bolts have a service life and can break at the most inopportune times...
http://www.magnaflux.com/Products/PenetrantInspection/SpotcheckVisible/SpotcheckKits/SK416Kit.aspx
BufordTJustice
12-02-11, 23:02
C158 is very hard to get in small lots, and 9310 is a substitute. 9310 is not quite as good as C158 for a bolt, but, it is not a bad material.
Bolts are weak spots on ARs, and I am very open to the concept of improving on the 50 year old mil spec design - the KAC E3 bolt seems clearly better.
Even Colt has advanced bolt and carrier designs which outperform the mil spec - and they submit them to things like the IC competition and M4 product improvement - but they just cannot put them into the existing contracts.
There is no doubt that better than mil spec bolts are real, but this particular one was probably not tested as much as a company like KAC would do simply due to the cost of 200,000 rounds of ammo.
I agree that the KAC E3 bolt is probably the pinnacle of current AR15 DI bolt innovation. I would love to use one if it didn't require that special barrel extension.
I'm currently running a Rainier Arms mil spec bolt (made of actual Carpenter 158 steel) and am very happy with it...no plans on changing it, in fact. Just curious about the new design around the cam pin hole (added material) and the 9310 steel.
Rsilver's can you give me a quick-but-cogent explanation of how 9310 is different from Carpenter 158? It's been difficult finding legit factual info on the topic. My search-fu has failed in producing any meaningful commentary on what actual makes the materials different.
Like I said, I'm fully confident that a fully mil spec Carpenter 158 bolt is GTG for the foreseeable future.
In the end, you need to make bolts from various alloys and then just shoot them - and look for peening and headspace growth over 10,000 to 20,000 rounds per bolt. It is very expensive to do such tests, but we do. I am aware of no alloy better than C158 for AR bolts. There may be some, but they are not 9310.
I also, as a sanity check, called Carpenter and asked their applications engineer on his opinions for using one vs the other on an AR bolt (Carpenter sells both materials). He could not see any possible way that 9310 was better than C158 for this application.
I am not sure of the issues related to increasing the diameter around the cam pin hole, but I would be concerned that the Superbolt seems to mention the dry-film lube on the cam pin. Seems like he is saying the fit was made tighter than normal so it seems like it has a reduced ID also.
BufordTJustice
12-03-11, 01:18
In the end, you need to make bolts from various alloys and then just shoot them - and look for peening and headspace growth over 10,000 to 20,000 rounds per bolt. It is very expensive to do such tests, but we do. I am aware of no alloy better than C158 for an AR bolts. There may be some, but they are not 9310.
I also, as a sanity check, called Carpenter and asked their applications engineer on his opinions for using one vs the other on an AR bolt (Carpenter sells both materials). He could not see any possible way that 9310 was better than C158 for this application.
I am not sure of the issues related to increasing the diameter around the cam pin hole, but I would be concerned that the Superbolt seems to mention the dry-film lube on the cam pin. Seems like he is saying the fit was made tighter than normal so it seems like it has a reduced ID also.
Thank you sir. :)
I did not realize that Carpenter sells BOTH. I glossed-over the blurb about mating the cam pin for the first time.....I agree that the ID of the cam pin hole must be reduced to the absolute minimum of the allowable spec...maybe even slightly smaller.
There are so many un-answered questions about the superbolt as well. I have learned that the heat treating process is precise and can easily be ****ed-up if somebody does not do it right. Same with the shot-peening. A Mil spec bolt is a known quantity.
If the superbolt is not using a superior material and it's not verified if any post machining processes have been performed at all....then I'd say that from a real-world perspective it seems like it doesn't have much to offer.
What do you think about a Carpenter 158 bolt that retains the greater outer diameter of the superbolt and also some of the radiusing of the bolt lugs to increase surface area?
Is there anything that would prevent a bolt made from Carpenter 158 from being machined to those design criteria?
http://www.cartech.com/ssalloysprod.aspx?id=3000
What do you think about a Carpenter 158 bolt that retains the greater outer diameter of the superbolt and also some of the radiusing of the bolt lugs to increase surface area?
Is there anything that would prevent a bolt made from Carpenter 158 from being machined to those design criteria?
I like the idea of certain changes using radii to make a C158 bolt last longer. I don't know if the larger OD will interfere though - I have not looked at that. But I am not stuck on mil-spec. For example, I know that nitriding a barrel - at least when done correctly (and not everyone does), is better than chrome-lined. I am open to nickel-boron, but only if it is does a certain way, and as far as I can tell *NO ONE* does it the way I think is correct.
Shot peening is very important, and should specifically be done to ASTM B851 specs. MPI is not important at all and I am actually offended by the stupidity of it.
MPI is not important at all and I am actually offended by the stupidity of it.
I just about fell out of my chair as I read this...
I thought MPI (along with HPT) was the holy grail for AR bolts.
MPI is not important at all and I am actually offended by the stupidity of it.
Hope he explains.
It was discussed here: https://www.m4carbine.net/showthread.php?t=81215
what are the list of companies that sell carpenter bolts?
BCM and Colt for sure
LMT and DD?
I am not sure of the issues related to increasing the diameter around the cam pin hole, but I would be concerned that the Superbolt seems to mention the dry-film lube on the cam pin. Seems like he is saying the fit was made tighter than normal so it seems like it has a reduced ID also.
Does anybody think its a benefit to have the cam pin fit loosely into the bolt?
Seems like the cam pin rocking around can be a contributor to extra stress on the already thin area of the bolt.
I just about fell out of my chair as I read this...
I thought MPI (along with HPT) was the holy grail for AR bolts.
Hope he explains.
It was discussed here: https://www.m4carbine.net/showthread.php?t=81215
Very good discussion with a few details left out to make a decent decision though, mostly due to company secrets (no negative connotation implied). Failure rate during HPT/MPI of current bolts would be nice to know before moving beyond that.
Very good discussion with a few details left out to make a decent decision though, mostly due to company secrets (no negative connotation implied). Failure rate during HPT/MPI of current bolts would be nice to know before moving beyond that.
As would the failure rate of bolts in the field that are batch tested.
I just about fell out of my chair as I read this...
I thought MPI (along with HPT) was the holy grail for AR bolts.
There are better ways to do test a bolt. One way would be to X-ray the steel PRIOR to it being manufacturered.
Since no one is doing that, MPI is what we have and what the Govt calls for.
C4
As would the failure rate of bolts in the field that are batch tested.
Yup.
There are better ways to do test a bolt. One way would be to X-ray the steel PRIOR to it being manufacturered.
Since no one is doing that, MPI is what we have and what the Govt calls for.
C4
Not sure why someone hasn't stepped up and started this or something similar. Lot's of room for good/better consumable items, including bolts.
I am open to nickel-boron, but only if it is does a certain way, and as far as I can tell *NO ONE* does it the way I think is correct.
What, don't like the heat treat?
AAC bolts are C158.
I looked into making the body diameter larger. I did not pull our drawings, but I measured a bolt - and the bearing surface was only 0.018 larger diam than the cam pin area - so that is just 0.009 per side. I don't think that leaves much room to make it larger - and I like the space for goop to go somewhere.
The difference between good and less good bolts are:
Good use C158, lesser uses 9310, and lesser still uses 8620.
Good has a thorough shot peen, to ASTM B851 specs. Less good uses shot peen that does not meet B851, and bad would be skipping shot peen. It is very important.
Good has a nice surface finish and was vibratory tumbled. Bad has areas where cracks can form.
Good has all specs dimensionally correct to the drawing. Bad has dimensions out of spec.
The problem is - people don't inspect their bolts to see if they are dimensionally in spec - so they are happy just to know it is MPI, which seems to be associated with being good. It is treated like a stamp of quality, but is by far the least important thing.
If 1 or 2 in a million bolts fails MPI, but 100,000 in a million fail a dimensional check - where should you spend your QC budget for screening parts?
By the way, even the bolt that does "fail" MPI is probably still a bolt with thousands of rounds of life left in it as it just has a microcrack on it that all AR bolts have after 3,000 to 5,000 rounds.
What I care about, aside from the obvious like using C158 and S2 extractors and extractor pins (which by the way - many use S7 without you knowing), is the detailed shot peening work.
If 1 or 2 in a million bolts fails MPI, but 100,000 in a million fail a dimensional check - where should you spend your QC budget for screening parts?
But as we discussed before (to which you never provided an answer to) was that we don't have that info available to us in order to make the right decision. Is it 1/1,000,000? Is it more, is it less? I was provided a number by someone who is someone that is certainly not 1/1,000,000.
I know - that is a problem that there is no public info on the failure rates. But it is close to 1 in a million.
That is to be expected, right? If a typical bolt does not form a micro-crack until 5000 rounds, what percentage of bolts would be expected to form a micro-crack after 1 proof round? Essentially none.
It was a good test 50 years ago, as lots of people did not believe the aluminum and plastic rifle was durable.
Here is something else to think about...
If you took a million bolts that were never MPIed...
and you took a million bolts that were MPIed and passed...
And you put these two million bolts into combat...
Would more bolts from the non-MPIed group fail before the bolts from the MPIed group?
In other words, would you statistically be able to tell which group was which based purely on the failure rate in the field?
Of course not.
Bad Hammer
12-03-11, 21:20
what are the list of companies that sell carpenter bolts?
BCM and Colt for sure
LMT and DD?
PSA advertises their bolts as being Carpenter 158 and shot peened, HPT and MPI.
Question for people who are more comfortable with MPIed bolts...
If you have 3000 rounds on your rifle, your bolt will probably fail MPI now. Under your own logic, are you not then compelled to discard your bolt? Why not get it re-MPIed every 1000 rounds and discard it upon failure?
PSA advertises their bolts as being Carpenter 158 and shot peened, HPT and MPI.
Ask them, Colt, DD, LMT, and BCM if their extractor and pin are made from S2 or S7. I actually don't know the answer, except Colt will be S2. For a smaller company, S2 is often unobtanium but 30% stronger. Rob_S should add S2/S7 to the chart.
I know - that is a problem that there is no public info on the failure rates. But it is close to 1 in a million.
As I said before, if it is that low I would take the non-HPT bolt any day of the week, in bulk, and have them x-ray'd through work (assuming free).
If you have 3000 rounds on your rifle, your bolt will probably fail MPI now.
I would hope not as the A2 spec calls for passing the MPI after the 6,000 round endurance test.
BufordTJustice
12-04-11, 00:39
what are the list of companies that sell carpenter bolts?
BCM and Colt for sure
LMT and DD?
Rainier as well.
http://www.rainierarms.com/?page=shop/detail&product_id=2633
I would hope not as the A2 spec calls for passing the MPI after the 6,000 round endurance test.
Ha. If only we all shot 20 inch rifle length gas. This from an M4:
http://www.dtic.mil/ndia/2006smallarms/taylor.pdf
Page 44:
"Most Bolts Subjected to Harsh Firing Schedules Will Show Initial Cracking Around 3,000 to 6,000 Rounds"
Sorry, I posted in the wrong thread.
This from an M4:
"
You didn't specify and I'm well aware of the litany of M4 faults, one of many reasons that I am not a fan of it.
constructor
02-29-12, 23:41
Anyone can look up the tensile and yield of the 2 materials as you can see they are very close in strength. Less than 2% difference in tensile and less than 5% in yield.
As far as 556 bolts, they will not be avail after about a week. We're busy running 6.8, 7.62x39 and 6BR bolts that can use the extra strength at the lugs.
9310-
http://www.latrobesteel.com/assets/documents/datasheets/9310.pdf
Carp 158-
http://cartech.ides.com/datasheet.aspx?i=101&E=100
Ask them, Colt, DD, LMT, and BCM if their extractor and pin are made from S2 or S7. I actually don't know the answer, except Colt will be S2. For a smaller company, S2 is often unobtanium but 30% stronger. Rob_S should add S2/S7 to the chart.
I had an extractor pin fail in a Bushmaster bolt a few years ago. It never quit working but was deforming from the exrtactor tension (had a D-ring) and a high round count.
It was found during a routine tear down for cleaning and replaced before it ever caused a malfunction but it certainly could have been an issue had it been left in much longer.
I've tried bolts out of the 3 materials referenced, Carpenter is basically just an old callout, it is very good and by only a small margin the best, but it was made a standard by a contract and it was only available to Colt. They made a deal where they would be the only company that could use the material from Carpenter.
8620 should never ever be used in a bolt, 9310 is an awesome material that is a good machineable alloy, it is used everywhere in other industries. Nearly the same for one piece piston carriers.
The only bolts I have seen fail are either lugs, or cam pin area elongating and developing a crack.
*This is what the shot peening fixes, I have no idea if the shot peening does anything anywhere else but that area is too thin and shot peening helps it, I wouldn't try increasing the bolt o.d. I would rather seem the cam pin od decreased and(.03") its material strength increased to match its current strength(its not a tough material currently).
High Rate shorter guns and it seems piston guns are harder on bolts. I had a magic bolt on a DI gun that had about 15k of machine gun mode, it was old and it could have died any second but I had to use its bolt to replace a bolt in a piston setup with a pretty loose carrier that was tilting badly and it ripped the top lug or two off the bolt in just a few rounds.
Anyone can look up the tensile and yield of the 2 materials as you can see they are very close in strength. Less than 2% difference in tensile and less than 5% in yield.
As far as 556 bolts, they will not be avail after about a week. We're busy running 6.8, 7.62x39 and 6BR bolts that can use the extra strength at the lugs.
9310-
http://www.latrobesteel.com/assets/documents/datasheets/9310.pdf
Carp 158-
http://cartech.ides.com/datasheet.aspx?i=101&E=100
It would seem that many folks into variants prefer your bolts due to their belief that the bolt is stronger and will hold up better to the heavier calibers, particularly when a larger bolt face is used.
On the other hand, those that use 5.56 for duty weapons prefer the time tested version because it is a known quantity in a rifle that your life may depend on.
I see both points. My question to you would be, is your 9310 bolt something you would personally recommend for a duty weapon? Also, you mentioned that the 5.56 bolts will only be available for another week or so. Is that a permanent change, or just temporary while you run more of the variant bolts?
constructor
03-01-12, 09:48
It would seem that many folks into variants prefer your bolts due to their belief that the bolt is stronger and will hold up better to the heavier calibers, particularly when a larger bolt face is used.
On the other hand, those that use 5.56 for duty weapons prefer the time tested version because it is a known quantity in a rifle that your life may depend on.
I see both points. My question to you would be, is your 9310 bolt something you would personally recommend for a duty weapon? Also, you mentioned that the 5.56 bolts will only be available for another week or so. Is that a permanent change, or just temporary while you run more of the variant bolts?
The only bolts in over 20 years I have had fail were Y/M, they broke at the cam pin hole. I've seen a few bolts from the largest producer of civilian ARs in this country that looked like the lugs were compressing, further inspection showed they were very soft. I know someone who built a grendel using a 7.62x39 bolt from the same company, after several stiff rounds the cases started taking the shape of a belted magnum, he checked and found the lugs were .008 shorter. I believe those bolts to be 8620 and not heat treated properly.
I checked into Carp 158 4 years ago, found out that all of the material was allocated to 2 companies that had DOD contracts to supply Colt and FN.
I ran shear tests on the carp bolts and ours, for all out strength our lugs are stronger. Fatigue test depending on the heat treat process also showed an improvement over the 158 bolts. I designed the bolts with a large radius on 3 sides of the lugs for a reason. There are other factors that are important other than just looking at the specs of the material. Some 9310 bolts on the market are or were too hard and brittle, the surface will develop cracks.
I've only made about 15000 bolts in the last 3 years, don't really need to push the sales, it's more to supply the rifles we build. There has not been 1 single bolt broken in 556,6.8 or 7.62x39.
There are some Fed teams using our 6.8s I have no doubt our bolts will last longer than any other 6.8 bolt on the market.
Something is going on with the 7.62x39, a couple of companies are testing heavily and asking for quotes on tens of thousands of bolts. It seems ours held up under full auto fire better than the rest.
As for the 556s it's too easy for us to buy Carp 158 bolts complete from a DOD contractor for less than it cost us to machine our bolts. I need our machine time for other projects, and I am dialing in our machining process on a new alloy that is apx 40% stronger than Carp 158 and 9310. It takes time to figure out the correct carbide grade, coating and chip breaker to turn out parts quickly.
I don't plan on making 556 bolts again unless we can't buy enough to supply our own builds just like what happened with the 6.8s, time will tell.
EzGoingKev
03-11-12, 14:38
I have a ARP bolt on my 6.8 aprox 1k rds on it.
So far so good!
A decent amount of time has gone by since you posted this, if you are still paying attention to this thread do you have any updates?
Bolts are weak spots on ARs, and I am very open to the concept of improving on the 50 year old mil spec design - the KAC E3 bolt seems clearly better.
The rounded lugs on the E3 bolt are what the AR should have had in the first place IMO.
The biggest thing that surprises me is that Remington retained the 90 degree angles on their bolts lugs in the SCAR instead of using a radius on the lugs.
Just FYI - 9310 seems to get bashed a bit for not being tried and true like C158, yet KAC makes their E3 bolts out of it. My guess is it has more to do with the heat treat and post machining processes than just material selection alone. KAC's also has bolts made of Aermet 100, how about them apples?
sinlessorrow
03-11-12, 20:09
The only bolts in over 20 years I have had fail were Y/M, they broke at the cam pin hole. I've seen a few bolts from the largest producer of civilian ARs in this country that looked like the lugs were compressing, further inspection showed they were very soft. I know someone who built a grendel using a 7.62x39 bolt from the same company, after several stiff rounds the cases started taking the shape of a belted magnum, he checked and found the lugs were .008 shorter. I believe those bolts to be 8620 and not heat treated properly.
I checked into Carp 158 4 years ago, found out that all of the material was allocated to 2 companies that had DOD contracts to supply Colt and FN.
I ran shear tests on the carp bolts and ours, for all out strength our lugs are stronger. Fatigue test depending on the heat treat process also showed an improvement over the 158 bolts. I designed the bolts with a large radius on 3 sides of the lugs for a reason. There are other factors that are important other than just looking at the specs of the material. Some 9310 bolts on the market are or were too hard and brittle, the surface will develop cracks.
I've only made about 15000 bolts in the last 3 years, don't really need to push the sales, it's more to supply the rifles we build. There has not been 1 single bolt broken in 556,6.8 or 7.62x39.
There are some Fed teams using our 6.8s I have no doubt our bolts will last longer than any other 6.8 bolt on the market.
Something is going on with the 7.62x39, a couple of companies are testing heavily and asking for quotes on tens of thousands of bolts. It seems ours held up under full auto fire better than the rest.
As for the 556s it's too easy for us to buy Carp 158 bolts complete from a DOD contractor for less than it cost us to machine our bolts. I need our machine time for other projects, and I am dialing in our machining process on a new alloy that is apx 40% stronger than Carp 158 and 9310. It takes time to figure out the correct carbide grade, coating and chip breaker to turn out parts quickly.
I don't plan on making 556 bolts again unless we can't buy enough to supply our own builds just like what happened with the 6.8s, time will tell.
If your bolts are so superior why settle?
You menion stopping production on 5.56 bolts because you can get "inferior" bolts cheaper.
Doesn't make much sense to me.
EzGoingKev
03-11-12, 21:01
Just FYI - 9310 seems to get bashed a bit for not being tried and true like C158, yet KAC makes their E3 bolts out of it.
Do you have a link to the source of this info?
The only bolts in over 20 years I have had fail were Y/M, they broke at the cam pin hole. I've seen a few bolts from the largest producer of civilian ARs in this country that looked like the lugs were compressing, further inspection showed they were very soft. I know someone who built a grendel using a 7.62x39 bolt from the same company, after several stiff rounds the cases started taking the shape of a belted magnum, he checked and found the lugs were .008 shorter. I believe those bolts to be 8620 and not heat treated properly.
I checked into Carp 158 4 years ago, found out that all of the material was allocated to 2 companies that had DOD contracts to supply Colt and FN.
I ran shear tests on the carp bolts and ours, for all out strength our lugs are stronger. Fatigue test depending on the heat treat process also showed an improvement over the 158 bolts. I designed the bolts with a large radius on 3 sides of the lugs for a reason. There are other factors that are important other than just looking at the specs of the material. Some 9310 bolts on the market are or were too hard and brittle, the surface will develop cracks.
I've only made about 15000 bolts in the last 3 years, don't really need to push the sales, it's more to supply the rifles we build. There has not been 1 single bolt broken in 556,6.8 or 7.62x39.
There are some Fed teams using our 6.8s I have no doubt our bolts will last longer than any other 6.8 bolt on the market.
Something is going on with the 7.62x39, a couple of companies are testing heavily and asking for quotes on tens of thousands of bolts. It seems ours held up under full auto fire better than the rest.
As for the 556s it's too easy for us to buy Carp 158 bolts complete from a DOD contractor for less than it cost us to machine our bolts. I need our machine time for other projects, and I am dialing in our machining process on a new alloy that is apx 40% stronger than Carp 158 and 9310. It takes time to figure out the correct carbide grade, coating and chip breaker to turn out parts quickly.
I don't plan on making 556 bolts again unless we can't buy enough to supply our own builds just like what happened with the 6.8s, time will tell.
This made sense to me.
I see no need to deviate from the standard 5.56 bolt given its decent reliability and ease of procurement. As long as you stick to known good manufacturers you should be fine.
Seems like the original idea came for his bolt because he couldn't find a dependable source for 6.8 bolts. I've been researching 6.8 lately and it seems to be a pain to find C158 bolts. Most tend to be 9310 so I've been looking at these for the slightly improved geometry.
constructor
03-12-12, 00:11
If your bolts are so superior why settle?
You menion stopping production on 5.56 bolts because you can get "inferior" bolts cheaper.
Doesn't make much sense to me.
The guy below you figured it out for you.
We can't keep up with the amount of machines we have.
556 bolts don't break that often.
We can buy C158 556 bolts cheaper than we can machine them.
I don't like running CNCs 12 hrs a day 7 days a week.
I don't need the money, rather spend time on the lake.
constructor,
Are you playing around with Aermet 100?
constructor
03-12-12, 23:18
constructor,
Are you plating around with Aermet 100?
No not Aermet, there are several metals that are similar in strength 290/250 range. When considering strength those numbers mean a lot but impact resistance and then heat treating them to the proper hardness to obtain overall toughness may be more important. Too soft, they compress. Too hard, they crack. In order to get to a 290 tensile/250 yeild the material must reach maximium hardness which isn't always the best for long term fracture toughness.
Typical bolt material is in the 180/160 range and hardly ever break due to lack of strength, it is the long term fatigue that kills a bolt.
EzGoingKev
05-14-16, 22:42
Bringing this back to life with a question for Constructor -
The cam pin hole is a known weak link on the AR bolt. You increase the diameter on your superbolts to make them stronger. You do not radius the edges of the cam pin holes in the bolt. Why leave them sharp as this makes them more like to start cracking there?
Haven't ever purchased any ARP products but when I built my first 7.62x39 AR the two most popular choices for an 'enhanced' bolt was ARP & LMT. ARP stopped making them when I finally got around to upgrading so I went LMT instead.
7.62x39 ARs are typically harder on their bolts which have thinner walls, so anyone who makes a good 7.62x39 bolt will make a top notch 5.56 bolt.
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