Those articles can help us understand how springs function. I've been looking for links that directly address coil spring function and failure, but haven't been all that successful.
The wikipedia article on
Spring_(device) above, is a good one, but almost none of the links address
how or why coil springs fail -- they just tell you how to recognize it when you see it. And, there is no real attention paid to how coil springs differ from other types of springs. (One of the articles lets someone who is more mathematically gifted than I predict when a given spring might fail, but that's a design issue, and not a practical calculation.)
The following is from
http://scienceworld.wolfram.com/physics/ElasticLimit.htmlMost solid objects subjected to an applied stress will return to their original shape and dimensions provided the stress is below a characteristic threshold for the material of which they are made. This limit is called the elastic limit (or sometimes yield point). Beyond this stress level, plastic deformation occurs, wherein the atomic or molecular structure changes shape permanently. With a compression coil spring, changing shape permanent is the same as a part of the spring dying -- losing its ability to do work. Some of the springs we've been discussing are intended to be used NEAR, AT or BEYOND their elastic limit.
Coil springs, whether they're compression or extension springs, work differently than leaf springs -- because more of the spring material is put to work than with leaf springs. A coil spring's material both bends and twists during normal functioning. With the types of potential spring failures being discussed here, we're most concerned about springs that are routinely asked to work at or near their
elastic limits Gun designers have created guns that are very small or hold a very large number of rounds. Only a relatively small number of gun designs really push some of their springs to these extreme limits -- but recoil springs in many sub-compact semi-autos only last for a fraction of the cycles of related full-size gun, while some "service pistols" may never need a recoil spring changed. High cap mag springs in some guns may seldom need to be replaced, if at all, but if you leave some very high-cap mags (18 or more rounds of 9mm) fully loaded, you will probably be replacing mag springs more frequently than in the past.
The "
compression spring stress" link skirts around the edge of our topic of concern, as does the link about
spring durability, which addresses failure due to fatigue. They all address how to know failure when you see it, but there's not a lot of guidance about how to prevent that failure.
A useful link that can be added to the ones above is
https://en.wikipedia.org/wiki/Yield_(engineering)#Definition The following link (which really addresses larger compression springs) offers insights into the forces that affect springs and how they can cause spring failure:
http://www.acewirespring.com/manufacturing_industry_fractures_compression_springs.htmlMost springs are designed to function over a long service life. And unless space inside the gun is an issue, springs can be made to operate in that optimal operating range almost indefinitely. Valve springs in car and truck engines can often cycle tens of millions of times over an engine's life without failure because, as used, they are never compressed too far. If a spring never gets near its elastic limit, it will lead a long service life.