Signs of high pressure test?

[lysander]

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

[prepare]

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.

[lysander]

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]

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]

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.
Attachment 70406

[lysander]

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]

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?

[lysander]

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.

[lysander]

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.

[prepare]

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.