View Full Version : Signs of high pressure test?
I bought a bolt that was advertised as Magnetic Particle Inspected and High Pressure Tested. I can see no evidence of this test. The bolt face and the front and back of the lugs appear pristine and there is no carbon on the bolt tail. Is this not as advertised or am I mistaken in the signs I expect to see?
Some companies sample test a portion of a batch and still mark the whole lot HPMPI as I've read here before. I personally wouldn't worry if the manufacturer is otherwise reputable. I've only had off brand bolts break prematurely.
High Pressure testing can be done with hydraulics, cheaper and cleaner . . .
And even if done with a cartridge, since the test set-up has no relative motion, there will be no evidence of the testing.
constructor
06-01-23, 20:48
I bought a bolt that was advertised as Magnetic Particle Inspected and High Pressure Tested. I can see no evidence of this test. The bolt face and the front and back of the lugs appear pristine and there is no carbon on the bolt tail. Is this not as advertised or am I mistaken in the signs I expect to see?
I've been trying to tell people for over 15 years the HPT is BS most of the time.
Manufacturers of bolts offer the MPI stamp for an extra dollar. The proof loads themselves cost $4 a shot so how do these companies mount barrels and bolts in a jig , fire a $4 test shot then inspect the bolt and barrel for $1 then stamp the bolt? They don't, they offer the stamp as a convenience service then it is up to the company manufacturing the firearms to test and discard bolts that do not pass. Back in the day Colt and FN were the only 2 companies that proof tested bolts and barrels.
Steel today is much better than it was back in the 60s and 70s, as long as manufacturers don't cut corners and use 8620 the steel should not have impurities that will effect the strength. IMO the heat treat used by the manufacturers will be more critical than quality of the alloy.
High Pressure testing can be done with hydraulics, cheaper and cleaner . . .
And even if done with a cartridge, since the test set-up has no relative motion, there will be no evidence of the testing.
That's a revelation. I don't know if this could honestly be desdribed as "proof fired" however which I think it also says. I'll have to check.
I've been trying to tell people for over 15 years the HPT is BS most of the time.
...
Steel today is much better than it was back in the 60s and 70s, as long as manufacturers don't cut corners and use 8620 the steel should not have impurities that will effect the strength. IMO the heat treat used by the manufacturers will be more critical than quality of the alloy.
In this article (https://www.arbuildjunkie.com/ar-bolt-carrier-group-basics-mike-mihalski/) Mike Mihalski of SOLGW states "People don’t realize that with well-made 158 carpenter steel bolts, about 3 percent of them will fail the HP test." This is what put the on the path of wanting an individually HP tested bolt. If HP testing can actually be had do you think it is of value?
constructor
06-01-23, 22:31
That's a revelation. I don't know if this could honestly be desdribed as "proof fired" however which I think it also says. I'll have to check.
In this article (https://www.arbuildjunkie.com/ar-bolt-carrier-group-basics-mike-mihalski/) Mike Mihalski of SOLGW states "People don’t realize that with well-made 158 carpenter steel bolts, about 3 percent of them will fail the HP test." This is what put the on the path of wanting an individually HP tested bolt. If HP testing can actually be had do you think it is of value?
Sure...IF they really have been tested.
I've never found a company that can prove they have been tested. Each bolt would need a serial number and a video of the test along with proof the ammo had been certified at a certain pressure. In the end it comes down to trust, who do you trust?
I tested the bolts I machined, at first all of them but after none were found to have cracks from MPI I started batch testing. I had Hornady make the proof loads for me which should have been 74000PSI. A short while later I called and asked Hornady for the data sheet on the loads, it said 92000psi and the testing was for 6.8 bolts which should be tested at a lower pressure than 5.56 bolts.
I stopped machining 5.56 bolts after doing a bunch of hyd destruction tests, I compared the bolts I was machining to Microbest bolts and both were well over the test limits. I've sold tens of thousands of 5.56 Microbest bolts over a period of 14 years and never had one break.
That's very different from "about 3 percent of them will fail" and I don't to how to reconcile it. Are you presently selling Microbest bolts?
constructor
06-02-23, 08:53
That's very different from "about 3 percent of them will fail" and I don't to how to reconcile it. Are you presently selling Microbest bolts?
I retired in 2017. Blackstone Arms is taking over my business including my Microbest account. After he gets the 5.56 products going he will sell Microbest bolts.
In all fairness I think the guy was saying 3% of some bolts that are high pressure tested will fail the MPI, not "will fail and break in the rifle". We don't know what type/brand of bolts he was referring to. Microbest will not make Grendel bolts and SOLGW sells Grendel bolts so...who makes them and do they also use the same brand 5.56 bolts?
I've never used SOLGW and they have a VERY limited description of their bolts. https://sonsoflibertygw.com/shop/solgwbolt556158c/
That's a revelation. I don't know if this could honestly be desdribed as "proof fired" however which I think it also says. I'll have to check.
If they aren't using hydraulics to test bolts, bolt makers are going about testing in a costly and inefficient manner.
With a bolt, the only thing you are worried about is the thrust load from the cartridge, the bolt really can't tell if that thrust comes from the firing of a test cartridge, or a pulse from a hydraulic ram . . .
If they aren't using hydraulics to test bolts, bolt makers are going about testing in a costly and inefficient manner.
With a bolt, the only thing you are worried about is the thrust load from the cartridge, the bolt really can't tell if that thrust comes from the firing of a test cartridge, or a pulse from a hydraulic ram . . .
That makes sense. Would a hydraulic test jig be faster than using a proof cartridge jig? I am guessing the answer is yes.
In manufacturing, saved time is profit.
Received confirmation from technical support. It's going back.
Found out that these have not been high pressure tested, that copy was put in and it should not have been. They actually have a way now of high pressure testing that does not require actual firing a round, Geissele utilizes this method on their bolts they say are high pressure tested.
But that bolt is not high pressure tested and that is being removed from the specs.
Is the pressure test a hard requirement, because from what I've been reading, it may just weaken the bolt. Buy from a reputable company and you should be good.
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Is the pressure test a hard requirement, because from what I've been reading, it may just weaken the bolt. Buy from a reputable company and you should be good.
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Welcome to the forum, master lurker!
That makes sense. Would a hydraulic test jig be faster than using a proof cartridge jig? I am guessing the answer is yes.
It probably wouldn't be faster, but it would certainly be cheaper to operate, you can reuse the hydraulic oil.
Is the pressure test a hard requirement, because from what I've been reading, it may just weaken the bolt. Buy from a reputable company and you should be good.
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The requirement for high pressure testing, either with M197 or SAAMI commercial equivalent is still on the Army's bolt drawing.
Understood, but as constructor has said, metallurgy is much better now than in the 50s and 60s. Since many companies aren't doing it anymore, i wonder if it's necessary, especially if it shortens the life of the bolt.
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Understood, but as constructor has said, metallurgy is much better now than in the 50s and 60s. Since many companies aren't doing it anymore, i wonder if it's necessary, especially if it shortens the life of the bolt.
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It shouldn't reduce the life of the bolt, if the bolt is up to snuff . . .
It's one event out of 10,000 plus or minus 2 or 3 thousand.
constructor
06-02-23, 16:37
The requirement for high pressure testing, either with M197 or SAAMI commercial equivalent is still on the Army's bolt drawing.
It says "high pressure test cartridge" , proof loads are higher pressure than M193 usually 25% higher than SAAMI max, that means apx 78000psi for the 5.56.
The big question is still can any company prove they high pressure test bolts other than Colt and FN. Now that SIG has a major contract they should have the same federal inspection requirements.
I retired in 2017. Blackstone Arms is taking over my business including my Microbest account. After he gets the 5.56 products going he will sell Microbest bolts.
In all fairness I think the guy was saying 3% of some bolts that are high pressure tested will fail the MPI, not "will fail and break in the rifle". We don't know what type/brand of bolts he was referring to. Microbest will not make Grendel bolts and SOLGW sells Grendel bolts so...who makes them and do they also use the same brand 5.56 bolts?
I've never used SOLGW and they have a VERY limited description of their bolts. https://sonsoflibertygw.com/shop/solgwbolt556158c/
Here's the description of the SOLGW BCG with all the details;
https://sonsoflibertygw.com/product-category/bolt-carrier-groups/
It says "high pressure test cartridge" (1) , proof loads are higher pressure than M193 usually 25% higher than SAAMI max (2), that means apx 78000psi for the 5.56.
(1) No.
The drawing 8448510, (19204), Bolt, Revision AD, dated 2011-04-21, says:
"8. EACH BOLT MUST WITHSTAND FIRING OF A HIGH PRESSURE TEST CARTRIDGE M197, OR SAAMI COMMERCIAL EQUIVALENT, WITHOUT EVIDENCE OF FAILURE. MAGNETIC PARTICLE INSPECT IN ACCORDANCE WITH ASTM E1444 USING A STANDARD 5 TURN MAGNETIZING COIL WITH A CURRENT OF 200 TO 300 AMPERES. CIRCULAR AND LONGITUDINAL CONTINUOUS MAGNETIZATION AND A WET FLUORESCENT SOLUTION SHALL BE USED."
(My emphasis.)
(2) SAAMI proof guidelines are higher than military.[/I][/U] According to SAAMI Z299.4 - Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Rifle Ammunition (available for free on SAAMI's website) give the proof range for .223 Remington as:
MINIMUM AVERAGE DEFINITIVE PROOF PRESSURE - 73,500 psi
MAXIMUM AVERAGE DEFINITIVE PROOF PRESSURE - 78,500 psi
M197 is not 78,000 psi, it's requirements are still the same 70,000 psi +/- 3,000 psi (average) they have been since at least 15 October 1964 (look it up, you should be able to find MIL-C-46936B on line). But, M97 is not what is used these days.
The current HPT cartridge for 5.56mm weapons is M197A1, covered under MIL-DTL-32530. The requirements for M197A1 are also below 78,000 psi; the average chamber pressure at 70 degrees F shall be 73,000 psi +/- 2,000 psi.
Here's the description of the SOLGW BCG with all the details;
https://sonsoflibertygw.com/product-category/bolt-carrier-groups/
I am sure they do a good job and all, but all that linked sight said, in a very long winded manner, was: "We make our stuff to print."
Literally, everything that site said they do is right on the drawings for the parts, saying, "You need to do this . . . "
constructor
06-02-23, 22:22
(1) No.
The drawing 8448510, (19204), Bolt, Revision AD, dated 2011-04-21, says:
"8. EACH BOLT MUST WITHSTAND FIRING OF A HIGH PRESSURE TEST CARTRIDGE M197, OR SAAMI COMMERCIAL EQUIVALENT, WITHOUT EVIDENCE OF FAILURE. MAGNETIC PARTICLE INSPECT IN ACCORDANCE WITH ASTM E1444 USING A STANDARD 5 TURN MAGNETIZING COIL WITH A CURRENT OF 200 TO 300 AMPERES. CIRCULAR AND LONGITUDINAL CONTINUOUS MAGNETIZATION AND A WET FLUORESCENT SOLUTION SHALL BE USED."
(My emphasis.)
(2) SAAMI proof guidelines are higher than military.[/I][/U] According to SAAMI Z299.4 - Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Rifle Ammunition (available for free on SAAMI's website) give the proof range for .223 Remington as:
MINIMUM AVERAGE DEFINITIVE PROOF PRESSURE - 73,500 psi
MAXIMUM AVERAGE DEFINITIVE PROOF PRESSURE - 78,500 psi
M197 is not 78,000 psi, it's requirements are still the same 70,000 psi +/- 3,000 psi (average) they have been since at least 15 October 1964 (look it up, you should be able to find MIL-C-46936B on line). But, M97 is not what is used these days.
The current HPT cartridge for 5.56mm weapons is M197A1, covered under MIL-DTL-32530. The requirements for M197A1 are also below 78,000 psi; the average chamber pressure at 70 degrees F shall be 73,000 psi +/- 2,000 psi.
Yeah I see min73,500-max78,500 same as the old 8448509 and that is what Hornady said their proof loads should be, apx 78,000. I stopped machining bolts in 2017. There are several companies I would not buy bolts from just reading their description and since I have a history with and know I can trust Microbest that is what I would buy and sell if I needed bolts. There is no need for me to try to find a HP tested bolt like the OP only to find out the company made a mistake and sent one that was not HP tested. I don't care how it's done but if you put 73,500 psi on a bolt face you will see the results of it.
ETA- I would rather buy a bolt from the real manufacturer than a reseller who may sell a different brand every month but laser etches their name on all of them. It's odd I never see many companies advertising AO Precision, Microbest or LW Schneider bolts
I am sure they do a good job and all, but all that linked sight said, in a very long winded manner, was: "We make our stuff to print."
Literally, everything that site said they do is right on the drawings for the parts, saying, "You need to do this . . . "
Not only does SOLGW check all the boxes but they also tell you specifically what those boxes are instead of just saying mil spec.
Checking all those boxes and sticking to a proven formula and being transparent is what I like about them. And that combination is very rare in this industry.
Yeah I see min73,500-max78,500 same as the old 8448509 and that is what Hornady said their proof loads should be, apx 78,000. I stopped machining bolts in 2017. There are several companies I would not buy bolts from just reading their description and since I have a history with and know I can trust Microbest that is what I would buy and sell if I needed bolts. There is no need for me to try to find a HP tested bolt like the OP only to find out the company made a mistake and sent one that was not HP tested. I don't care how it's done but if you put 73,500 psi on a bolt face you will see the results of it.
ETA- I would rather buy a bolt from the real manufacturer than a reseller who may sell a different brand every month but laser etches their name on all of them. It's odd I never see many companies advertising AO Precision, Microbest or LW Schneider bolts
Consumers cannot buy directly from the manufacturer.
constructor
06-03-23, 09:28
Consumers cannot buy directly from the manufacturer.
I sold direct, Maxim does, LWRC , pretty sure JP does, Y/M , Aero Precision, LMT, Sharps, I'm pretty sure those companies make their own bolts and sell them.
Resellers should tell you who made the bolts instead of sticking their own name on them like they made the bolts.
Resellers should tell you who made the bolts instead of sticking their own name on them like they made the bolts.
What do you think of this? https://arftac.com/microbest-ar15-5-56-c158-mpi-bolt-carrier-group-complete/
I sold direct, Maxim does, LWRC , pretty sure JP does, Y/M , Aero Precision, LMT, Sharps, I'm pretty sure those companies make their own bolts and sell them.
Resellers should tell you who made the bolts instead of sticking their own name on them like they made the bolts.
I meant direct from Microbest.
That being said, from what I understand just because a certain brand sells a Microbest BCG that doesn't mean it's the same specs as a TDP BCG.
constructor
06-03-23, 11:30
I meant direct from Microbest.
That being said, from what I understand just because a certain brand sells a Microbest BCG that doesn't mean it's the same specs as a TDP BCG.
If you don't like Microbest don't buy them but if you buy Rubber city, spikes, toolcraft, PSA, Y/M or any nitride treated bolt and wont buy a Microbest you may want to dig a little deeper.
Microbest makes the same parts the same way for every customer, they don't change anything for anyone. They have part numbers, you send in a PO for the part number.
In 14 years I talked to the VP twice, he said they make apx 40,000 bolts a month and 30,000 carriers, they make all the small parts to build complete BCGs along with many other small parts of ARs. They make mil spec parts for many companies and you're right the are mainly concerned with filling big orders but I could send in a PO for 200 bolts or 144 BCGs and they will fill the order.
Microbest makes the same parts the same way for every customer, they don't change anything for anyone. They have part numbers, you send in a PO for the part number.
Interesting...
So as a manufacturer you can basically order 100% TDP BCG's from Microbest?
constructor
06-03-23, 11:55
What do you think of this? https://arftac.com/microbest-ar15-5-56-c158-mpi-bolt-carrier-group-complete/
I don't know anything about the reseller but if it's a microbest BCG it will be good to go.
I think any bolt from AO Precision, Microbest or LW Schneider will be good. I'm not sure who makes BCMs bolts but the tool path on the bolts looks like Microbest. I would also trust LMT.
If I feel like working I can make my own but if I'm buying it would be from one of those 5 companies.
constructor
06-03-23, 12:09
Interesting...
So as a manufacturer you can basically order 100% TDP BCG's from Microbest?
From what the VP told me in 2008 yes, they have been the same BCGs except for the last extractor spring change when they went to the piano wire spring.
Yeah I know Colt owns the TDP and no one should know the true details right? If that is true no one is making BCGs to the TDP. Colt changed to piano wire springs and MB did about the same time.
BTW I don't know anything about SOLGW.
. . . except for the last extractor spring change when they went to the piano wire spring.
. . . Colt changed to piano wire springs and MB did about the same time.
When did this happen?
According to the information I have from Rock Island, the extractor spring has been music wire spring, ASTM A228 since at least 1964.
The diameter and/or number of coils has changed a time or two, and even the number of springs has changed*, but the material has always been ASTM A228, music wire.
___________
* The first extractor spring was a single 5 coil spring, the second design of the extractor spring assembly was two nested springs. The third design was the one with the white, then blue insert. The forth design was the same spring as the third, but with a stiffer black insert, we are currently on the fifth design with the new copper washed spring and the same insert as the forth.
constructor
06-03-23, 21:32
When did this happen?
According to the information I have from Rock Island, the extractor spring has been music wire spring, ASTM A228 since at least 1964.
The diameter and/or number of coils has changed a time or two, and even the number of springs has changed*, but the material has always been ASTM A228, music wire.
___________
* The first extractor spring was a single 5 coil spring, the second design of the extractor spring assembly was two nested springs. The third design was the one with the white, then blue insert. The forth design was the same spring as the third, but with a stiffer black insert, we are currently on the fifth design with the new copper washed spring and the same insert as the forth.
It's the same stuff, it looks like copper instead of the black springs( Chrome Silicon wirestock). The current springs look like this
70396
Does anyone know the testing standards used by L.W. Schneider? For those who do not know, they are a parts source for multiple firearm manufacturers.
It's the same stuff, it looks like copper instead of the black springs( Chrome Silicon wirestock). The current springs look like this
70396
Chrome silicon was never in the Colt TDP . . . Always music wire ASTM A228.
constructor
06-03-23, 22:52
Chrome silicon was never in the Colt TDP . . . Always music wire ASTM A228.
IIRC I noticed the spring change in Microbest bolts around 2009-2010, my shop was still in Colorado at that time. I thought they were music wire/piano wire or whatever you wish to call it in the beginning(m16) but were changed to Cs to try to fix the extraction issues with carbine gas barrels. They still say CS springs will outlast a piano wire spring by 4 times and provides 80% more force. BCM, Brownells, Tubbs and many others still sell them(CS) as an upgrade.
Do you have a copy or copies of the Colt TDP of the years involved from 1966 to present?
As stated above, there have been five (5) iterations of the extractor spring assembly
P/N 61568 - Spring. A single 5 coil spring, referenced in Air Force Manual 50-12, dated 30 Aug 1963, and "The Black Rifle"
P/N ??? - two nested springs, the outer of which might be 61568. There are a number of references to "extractor springs" in PS Magazines from the late 1960s, and "Report of the M16 Rifle Review Panel, Appendix 11, M16 Product Improvement Modifications" (available on line)
P/N 8448755 - Spring Assembly, Extractor, consisting of P/N 8448754 - Insert, and P/N 8448753 - Spring, Extractor. This is the blue rubber insert and silver or black spring (no color is specified)
P/N 12972692 - Spring Assembly, Extractor, consisting of P/N 1297293 - Buffer, Extractor, and 8448753 - Spring, Extractor. This was released in December 1995 as the initial extractor spring assembly for the M4 carbine, this is the black rubber insert and black (or silver) spring.
P/N 13004786 - Spring Assembly, Extractor, consisting of P/N 12972693 - Buffer, Extractor, and P/N 12999901 - Spring Extractor. This was released in January 2003, and is the latest assembly with the black rubber insert and copper colored spring.
I have access to all but the first two drawings, but I am not at liberty to give them out, even though you can find your own copies online with a little digging. Trust me, the extractor spring has always been music wire.
As to this:
They still say Chrome Silicon (CS) springs will outlast a piano wire spring by 4 times and provides 80% more force.
IT IS ONLY TRUE AT TEMPERATURES ABOVE 300° F, and since the extractor spring is not maintained at that kind of temperature, this is a non-issue. Also, many people compare CS to carbon steel and say that it is better than music wire. "Carbon steel" springs are not the same as "music wire" springs.
But wait, there's more.
Music wire springs generally have better fatigue life at room temperature (below 250° F) due to the fact that music wire can maintain a better surface finish than CS or plain carbon steel wire. Also, the belief that CS springs are stronger is not necessarily true. It is only true at wire diameters larger than 0.08" (the thickest spring in the AR is the Action Spring, and that's only 0.078" in diameter).
https://cdn-0.mentoredengineer.com/wp-content/uploads/2019/11/strengthvsdia.png
Generally speaking, music wire is the best choice for springs unless you require:
- the spring is going to live in an environment with a temperature above 300° F or below 0° F.
- the spring is going to be subjected to a corrosive environment.
- the spring wire is going to be larger than 0.080".
Further, CS is no better at resisting corrosion than music wire, there is no reason it would be used over music wire or stainless steel in any rifle. And, never replace stainless steel spring with CS springs, you won't like it.
constructor
06-04-23, 09:26
The only complete TDP ever released was in 1996 when they wanted bids for the M4 SOPMOD project.
Are you saying all springs were music wire but could be black or copper colored? I didn't remove the springs and send them to a lab for analysis, just noted the extractor springs in the Microbest bolts changed to a copper color.
Thanks for the history of springs.
I don't seem to have issues with extractor springs, I have a big bag that probably had 10,000 in it to start. I installed them in the bolts we machined and shot, can't ever recall one failing or having a customer call and say one failed.
As stated above, there have been five (5) iterations of the extractor spring assembly
Yet another of your posts I am saving for reference. Thank you.
constructor
06-04-23, 10:21
Lysander,
Do you go by ThELioN70x7 or M4Guy (same guy different accounts) on another forum or Hueyville? Your style seems familiar.
The only complete TDP ever released was in 1996 when they wanted bids for the M4 SOPMOD project. (1)
Are you saying all springs were music wire but could be black or copper colored? (2) I didn't remove the springs and send them to a lab for analysis, just noted the extractor springs in the Microbest bolts changed to a copper color.
Thanks for the history of springs.
I don't seem to have issues with extractor springs, I have a big bag that probably had 10,000 in it to start. I installed them in the bolts we machined and shot, can't ever recall one failing or having a customer call and say one failed.
1) . . . that was acknowledged by the USG . . . I have found drawings dated 2010 on the web.
2) All are made from music wire, ASTM A228, however, the wire diameter and number of coils vary, which is why they color code them. The current copper-colored spring, P/N 12999901, is 4 coils of 0.026" diameter wire, the old (black) spring, P/N 8448753 is 4 coils of 0.022" diameter wire, the first spring, P/N 61568, was 5 coils of approximately 0.018 to 0.020" diameter wire.
Same with the rubber inserts, the blue ones (8448454) were fluorosilicone, 60 shore, the black ones (12972693) are Buna-N, shore 80
I would like to see some recent endurance and destructive tests comparing the Sprinco Green extractor springs to the Colt Gold as well as the Sprinco action springs to the mil-spec stainless steel action springs.
The Sprinco Green extractor spring and A5 action spring are in a lot guns now. It's pretty all SOLGW uses and I'm unaware of any failures.
The current Colt gold extractor spring lasts at least 32,400 rounds between failures in testing, possibly as more than 36,000 rounds.
The stainless steel action spring should last in excess of 36,000 rounds.
So, I see no reason to go looking for something to solve non-existent problems (and one that will be more expensive and potentially create problems). In my opinion, Chromium-Silicon springs are the second worst choice for springs in the AR. CS is no better than music wire at normal temperatures, and far less corrosion resistant than stainless steel, and generally more expensive.
"Chrome Silicon wire is used in very high stress applications such as, NASCAR, Formula One, Moto GP & Pro Stock racing motor valve springs."
This is a stupid statement, and completely irrelevant. In a engine the oil temperature normally stabilizes around 250° F, so that means just about every part in contact with the oil will have a temperature around 250°, including the valve springs, which actually will be higher as they are also sucking heat out of the valves themselves, so engine springs spend their entire working life at 250+ degrees. Further, valve spring live in an oil bath, the threat of corrosion is minimal.
If you shoot seven 30-round magazines in full auto as fast as you can in an M4, you bolt temperature will peak around 250°, and most of the springs in a AR are left exposed to the ambient environment. Vast difference in environment, vast difference requirements.
Then there is cost, how much longer life do you get for the extra cost. If it cost twice as much you better get more that twice the life.
constructor
06-05-23, 12:56
I would like to see some recent endurance and destructive tests comparing the Sprinco Green extractor springs to the Colt Gold as well as the Sprinco action springs to the mil-spec stainless steel action springs.
The Sprinco Green extractor spring and A5 action spring are in a lot guns now. It's pretty all SOLGW uses and I'm unaware of any failures.
I don't have time to sit and research like some do and cell service isn't so great out on the boat but I will say I have used Sprinco buffer springs(red, orange and green) since Alan first started around 2008 and never had issues, they are still running in the rifles as of Saturday.
I am in the camp that believes barrels should be ported correctly to start with and H, H2, H3 buffers and strong springs were made/designed to fix barrels that were over-gassed however I also believe that rifles can be matched(planned), port and buffer weight so that when the rifles get hot, dry and dirty they will continue to function.
For normal 14.5 and 16" rifles with a mid length gas system should run a .073" port but you could run a .076" port in conjunction with a Springco red spring and a H2 buffer and get apx the same carrier speed and it would more than likely keep stripping rounds and running when hot, dry and dirty.
I've been building ARs since the late 90s and never had a spring of any kind fail, I've had bolts break at the cam pin hole and extractor, I had a lug break off an early Grendel bolt(2005). I've had disconnectors fail , I've had drop in triggers fail...no springs.
I am curious why it takes an extractor spring, a rubber buffer and a rubber O-ring to make an extractor work but not curious enough to waste time researching it.
constructor
06-05-23, 17:05
OP, this is what a proof load looks like, just what I had left when I closed the shop and I pulled the bullets.
If the bolt has been tested you can tell without a doubt.
70406
I am curious why it takes an extractor spring, a rubber buffer and a rubber O-ring to make an extractor work but not curious enough to waste time researching it.
Well, the o-ring isn't required for rifles and carbines with the copper colored springs . . .
Why the insert.
During chambering, the extractor snaps over the rim of the cartridge case, this is a relatively violent action and slaps the spring rather hard. In some cases, it can be violent enough that the spring goes into coil bind (goes solid). And as you know, a spring compressed solid on a regular basis will have a short, unhappy life.
The solution to this is that the spring rate be increased. The ways to increase the rate of a coil spring are: 1) larger wire diameter, 2) smaller coil diameter, or 3) reduce the number of coils.
Since the distance under the extractor is limited, a larger wire diameter (1) would just make matters worse as the solid height of the spring would be increased. The spring is already near the limit of minimum diameter (2), and even if you did reduce the OD some more, you run into stability issues, unless you redesigned the extractor/bolt interface. And, since the extractor spring has four (4) coils with closed ground ends, only two (2) of the coils are active, so there aren't any coils to eliminate.
So, we are in a quandary,we need a stiffer spring, but we can't make one that fits. The solution is two springs in parallel so the spring rates add, and the only way they would fit is nest them.
You could have a inner spring (like the AR-10/AR .308), But that would be a very small OD spring and might have stability issues, or coil interference. Or, you go the cheaper route and have a stiff rubber insert.
constructor
06-05-23, 18:12
Well, the o-ring isn't required for rifles and carbines with the copper colored springs . . .
Why the insert.
During chambering, the extractor snaps over the rim of the cartridge case, this is a relatively violent action and slaps the spring rather hard. In some cases, it can be violent enough that the spring goes into coil bind (goes solid). And as you know, a spring compressed solid on a regular basis will have a short, unhappy life.
The solution to this is that the spring rate be increased. The ways to increase the rate of a coil spring are: 1) larger wire diameter, 2) smaller coil diameter, or 3) reduce the number of coils.
Since the distance under the extractor is limited, a larger wire diameter (1) would just make matters worse as the solid height of the spring would be increased. The spring is already near the limit of minimum diameter (2), and even if you did reduce the OD some more, you run into stability issues, unless you redesigned the extractor/bolt interface. And, since the extractor spring has four (4) coils with closed ground ends, only two (2) of the coils are active, so there aren't any coils to eliminate.
So, we are in a quandary,we need a stiffer spring, but we can't make one that fits. The solution is two springs in parallel so the spring rates add, and the only way they would fit is nest them.
You could have a inner spring (like the AR-10/AR .308), But that would be a very small OD spring and might have stability issues, or coil interference. Or, you go the cheaper route and have a stiff rubber insert.
Why do all these "tier one" rifle builders use a spring , a buffer and a O-ring? You been quoting the TDP like the bible for 3 days, does the TDP say use a spring a buffer and a o-ring?
Oh, and there is another big advantage to an elastomeric over a traditional coil spring: no coils, no coil bind.
Careful design of the spring insert can be done so that the insert "goes solid", it does so at a height that is greater than the solid height of the coil, outer spring. This ensures the coil spring never goes solid.
Why do all these "tier one" rifle builders use a spring , a buffer and a O-ring? You been quoting the TDP like the bible for 3 days, does the TDP say use a spring a buffer and a o-ring?
The M16/M4 extractor has one spring, and one rubber insert/buffer, no o-ring.
Why do people people still after 20 years still put in an o-ring?
Because people were sold on it as "better" on the internet, and now nobody will will believe you if you give them the facts and get upset at manufacturers if they don't put one in.
The o-ring came about because the original M4 extractor spring, P/N 12972692, needed a bit more stiffness when used in the Navy's Mk 18 CQBR and NSWC Crane, so they stuck cheap and simple o-ring to increase the spring rate, same as the original rubber insert. It was never intended by Colt, or the Army as a permanent fix, so spring assembly, extractor, P/N13004786, was designed. The funny thing is, the copper spring came about the same time the o-ring did, at least for the military.
The even funnier thing is that the problems that necessitate the o-ring really only an issue with short barrel carbines in full automatic. Your average semi-automatic 16" carbine, that is properly gassed, wouldn't miss the o-ring, even with the old-style spring assembly.
The current Colt gold extractor spring lasts at least 32,400 rounds between failures in testing, possibly as more than 36,000 rounds.
The stainless steel action spring should last in excess of 36,000 rounds.
So, I see no reason to go looking for something to solve non-existent problems (and one that will be more expensive and potentially create problems). In my opinion, Chromium-Silicon springs are the second worst choice for springs in the AR. CS is no better than music wire at normal temperatures, and far less corrosion resistant than stainless steel, and generally more expensive.
"Chrome Silicon wire is used in very high stress applications such as, NASCAR, Formula One, Moto GP & Pro Stock racing motor valve springs."
This is a stupid statement, and completely irrelevant. In a engine the oil temperature normally stabilizes around 250° F, so that means just about every part in contact with the oil will have a temperature around 250°, including the valve springs, which actually will be higher as they are also sucking heat out of the valves themselves, so engine springs spend their entire working life at 250+ degrees. Further, valve spring live in an oil bath, the threat of corrosion is minimal.
If you shoot seven 30-round magazines in full auto as fast as you can in an M4, you bolt temperature will peak around 250°, and most of the springs in a AR are left exposed to the ambient environment. Vast difference in environment, vast difference requirements.
Then there is cost, how much longer life do you get for the extra cost. If it cost twice as much you better get more that twice the life.
According Sprinco description, May easily be the only extractor springs needed for the life of your bolt!
Action Spring;
Reduced operating cost as replacement springs are not needed during the life of your upper receiver assembly. Less downtime and fewer trips to the armorer for spring replacement, in fact, this will most likely be the only buffer spring you will ever need for the duty cycle of your carbine or rifle!
500,000 cycles per Allen from Sprinco is the number given out in the SOLGW armorer class.
According Sprinco description, May easily be the only extractor springs needed for the life of your bolt!
The life of a bolt is anywhere from 12,000 to 20,000 rounds, a regular copper-colored spring lasts about 32,000 to 36,000 rounds. The copper colored spring can last up to three times longer than the bolt . . .
A USGI stainless steel action spring will last at least 36,000 rounds and cost about $4.00 to $5.00.
Your $20.00 Springco Spring will need to last 144,000 rounds in order to be a better value than a $5.00 spring, but you will have to shoot all 144,000 rounds, maybe more, to recoup the investment. That's poor economics.
The life of a bolt is anywhere from 12,000 to 20,000 rounds, a regular copper-colored spring lasts about 32,000 to 36,000 rounds. The copper colored spring can last up to three times longer than the bolt . . .
A USGI stainless steel action spring will last at least 36,000 rounds and cost about $4.00 to $5.00.
Your $20.00 Springco Spring will need to last 144,000 rounds in order to be a better value than a $5.00 spring, but you will have to shoot all 144,000 rounds, maybe more, to recoup the investment. That's poor economics.
Understood on the economics.
In terms of service life both springs are highly regarded.
The only negative that I'm aware of regarding Sprinco is something about action spring corrosion some years ago. Don't have any details though...
The only negative that I'm aware of regarding Sprinco is something about action spring corrosion some years ago. Don't have any details though...
Well, stainless steel is the best material choice for an action spring, due to it corrosion resistance.
Well, stainless steel is the best material choice for an action spring, due to it corrosion resistance.
What are the chrome silicon corrosion resistance properties?
What are the chrome silicon corrosion resistance properties?
No better than carbon steel, about on par with music wire . . .
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