[JohnKSa]

Bill,

Chang's article is actually a refutation of the claims in another article. His refutations are indented while the original article is justified against the left side of the page.

He does, in fact, acknowledge that springs do weaken-- he uses the term fatigue.

"However, fatigue can definitely occur due to cyclic loading below the static yield strength of the material. Even absent surface stress risers (e.g., notches), fatigue crack nucleation can occur at grain boundaries, second-phase particles, twin boundaries, and other microstructural features which exist normally."

However, he also believes that springs can't be weakened by simply compressing them and leaving them compressed. That, unfortunately, is demonstrably false. I've seen at least two experiments with carefully measured results (one of which I've posted on this thread) demonstrating that under certain circumstances leaving a spring compressed can weaken it and leaving it compressed longer weakens it more. The effect is not only repeatable, it tracks well between the variety different springs tested showing that it's fairly consistent across a number of springs of varying manufacture and quality.

Originally Posted by Scubasimmons

Article is wrong constant stress below the yield limit will result in creep.

I agree, there's simply too much experiential and conclusive experimental evidence to conclude otherwise.

Originally Posted by chack

Why doesn't anyone change the springs on their rifles?

First of all, no one has said that no one changes their rifle springs.

Second, there are very few centerfire rifles that have "recoil" springs. That is, the springs are not absorbing "recoil", they are simply bolt return springs. That's a much less stressing job for a spring.

Why is it that some of y'all change out recoil and mag springs but not extractor, firing pin, and sear springs?

How many manufacturers recommend replacement of extractor, firing pin and sear springs on a regular basis? Off the top of my head, I don't know of any. On the other hand, I know of several manufacturers who formally or informally recommend replacement of recoil springs on a regular basis based on the number of rounds fired. I just finished reading an article about a new Kimber compact pistol that indicated that Kimber recommends replacing the recoil spring every 1000 rounds but made no mention of other springs that needed regular replacement.

For what it's worth, I don't replace magazine springs on a regular basis although I would if I found I were having repeated failures at reasonably regular intervals or if a manufacturer were to recommend a replacement schedule.