Recoil Springs

[billrd]

They are rated in pounds. How do you test/measure them. I used to test by measuring but that does not work anymore as they are pretty much the same length but the number of coils varies. I used to put them in a tube and put a weight on top and see how far they would depress - that gives me a relative strength indication. I want to know how to measure a 7 lb spring for instance. I guess I could use my tube method with a new spring for comparison but not sure that's valid as the spring performance while operating is dynamic - 2 springs might measure the same but not work the same. Is there a spec or something that says a spring under a given pressure would have a minimum length or ??
Please try not to point out to me that if it works who cares?
For one thing springs rarely fail catastrophically but get weaker with use and heat - a high rate of functioning generates a lot of heat and the strength will be affected while it's cycling. Kind of like magazines - they work fine until the failures start increasing - would like to be able to anticipate those failures. I have had them occur at a VERY bad time and had never failed prior to that.
Thanks,
Bill

[blockfort]

I would imagine it's inch-pounds, that's a pretty standard way to spec a spring. A 7lb spring should compress 1 inch with 7lbs of weight on it.

But some springs are progressive, so the compression is not linear, they may seem weaker at small compression values, and stiffer at high values.

[krwada]

Recoil Springs

They are rated in pounds. How do you test/measure them. I used to test by measuring but that does not work anymore as they are pretty much the same length but the number of coils varies. I used to put them in a tube and put a weight on top and see how far they would depress - that gives me a relative strength indication. I want to know how to measure a 7 lb spring for instance. I guess I could use my tube method with a new spring for comparison but not sure that's valid as the spring performance while operating is dynamic - 2 springs might measure the same but not work the same. Is there a spec or something that says a spring under a given pressure would have a minimum length or ??
Please try not to point out to me that if it works who cares?
For one thing springs rarely fail catastrophically but get weaker with use and heat - a high rate of functioning generates a lot of heat and the strength will be affected while it's cycling. Kind of like magazines - they work fine until the failures start increasing - would like to be able to anticipate those failures. I have had them occur at a VERY bad time and had never failed prior to that.
Thanks,
Bill

Recoil springs are rated / measured by the amount of force it takes to hold the spring in full compression.

In general, you will need a jig or measuring device to do this. Many gunsmiths have such a device or jig.

[billrd]

Thanks - I'll try it.

[billrd]

Thank You.

[ar15barrels]

when we checked valve springs, we compress them to their installed (closed) length and that showed us the seat pressure.
Then, we would compress them to full bind to be sure that their full bind length was less than our full-open length once they are installed on the head.



I woud think that the same technique applies to recoil springs.