Extractor spring strength ranking

[Disciple]

How do the strengths of these extractor springs rank? Colt copper, Sprinco 4 coil, Sprinco 5 coil, BCM.

[alx01]

How do the strengths of these extractor springs rank? Colt copper, Sprinco 4 coil, Sprinco 5 coil, BCM.

Spinco 5 Coil > BCM

Haven't used Sprinco 4-coil.

One thing I don't particularly like about Spinco's 5-coil spring vs. BCM for example, is that it requires quite a bit for force to set into pocket. It feels like a wider end is a bit oversized. BCM on the other hand snaps in perfectly. I've used both extensively. Both work great and I wouldn't hesitate to use either. I don't have a specific preference.

I would also be interested if someone could rate Specialized Armament green extractor spring. It's only available from them.
https://www.specializedarmament.com/...g-assembly-sa/

sa42602.jpg

[georgeib]

I'm sure someone will come along with a better understanding, but AFAIK Colt, BCM, and Sprinco 4 coil are equal, whereas the 5 coil is approximately 20% heavier.

[lysander]

The correct spring data for the 4-coil gold/copper spring is:

Load at a compressed length of 0.140" = 3.6 +/-0.6 lbs
Load at a compressed length of 0.112" = 8.4 +/-0.8 lbs

The obsolete 4-coil spring was:

Load at a compressed length of 0.140" = 2.0 +/-0.2 lbs
Load at a compressed length of 0.112" = 4.2 +/-0.4 lbs

The correct black buffer is nitrile-butadiene (BUNA-N), shore hardness of 80

[Disciple]

Thanks lysander, as always. How do you feel about music wire versus chrome silicon in this application?

[prepare]

Has anyone tested the load on Sprinco 4 and 5 coil springs?

[alx01]

The correct spring data for the 4-coil gold/copper spring is:

Load at a compressed length of 0.140" = 3.6 +/-0.6 lbs
Load at a compressed length of 0.112" = 8.4 +/-0.8 lbs

The obsolete 4-coil spring was:

Load at a compressed length of 0.140" = 2.0 +/-0.2 lbs
Load at a compressed length of 0.112" = 4.2 +/-0.4 lbs

The correct black buffer is nitrile-butadiene (BUNA-N), shore hardness of 80

What are the values for the ejector spring? Are there a dimensional specifications for the ejector spring or just load?

[lysander]

Thanks lysander, as always. How do you feel about music wire versus chrome silicon in this application?

In ALL AR-15 applications there is absolutely NO REASON to use chrome-silicon wire, period.

There is absolutely no difference between music wire and chrome-silicon wire, except performance at high temperature. Two springs, one music wire, and one C-S made to the same dimensions, will have the same spring rate, same stress factors, same life, at temperatures below 300 degrees F.

If you need a valve spring to live inside and engine, yes, it might have to withstand a constant heat soak of 300 F. If your gun spring is uniformly above 300 F, your gun is on fire and you don't need to worry about the spring life.

[lysander]

What are the values for the ejector spring? Are there a dimensional specifications for the ejector spring or just load?

Music wire, ASTM A228
Wire Dia = 0.024
OD = 0.103
Total coils = 27
Square-ground ends
Load at a compressed length of 0.850" = 2.95 +/-0.3 lbs
Load at a compressed length of 0.784" = 5.50 +/-0.25 lbs


The dimensions for the extractor springs are:

Music wire, ASTM A228
Wire Dia = 0.026
OD = 0.151
Total coils = 4
Square-ground ends
Last coil one end expanded to 0.165"

[Disciple]

If you need a valve spring to live inside and engine, yes, it might have to withstand a constant heat soak of 300 F. If your gun spring is uniformly above 300 F, your gun is on fire and you don't need to worry about the spring life.

Heat was my concern. Happy to hear it's irrelevant. What temperature can the bolt reach under full-auto fire?