...As a structural engineer who understands physics quite well, I have seen no evidence or proof to believe that constant compression will wear out a properly designed spring.
And what is a
properly designed spring? Is it one that lasts a long time without replacement, or one that lets a magazine hold an extra round or two in the space originally intended to hold fewer rounds? I've been told there aren't any free lunches... and the trade-off between the first example and the second has to have real-world costs.
Nobody is saying that all mag springs will fail from staying compressed. In fact, many mag springs aren't highly stress when compressed. That is certainly true of 7-round 1911 single-stack mags. It seems less true with some sub-compact mags, like the Kahr P9, with which I've had some experience, and with some hi-cap mags. That said, I've never had a 10-round mag spring fail in a full-size 9mm handgun.
As I have noted before, the same mag spring is used in the CZ 10-round and CZ 17-round mag. One full compression cycle with the 17 round mag causes that spring to lift 70% more material than the 10-round mag, and the 17-round mag spring clearly must be compressed far more fully than the 10-round spring.
Would a reasonable person really expect those two springs to have the same service life in normal usage, if we count only the cycles (from full to empty)? They are, afterall, the same springs and same number of cycles, but arguably a much different work load. How about if the the two mags are stored fully loaded? Is the stress on the springs the same? I'd argue that when stored, those springs are still working (in one sense, at least), pressing the rounds in the tube up against the mag's feedlips.
Springs
will degrade over time. How quickly they degrade will depend on WHEN they are used (i.e., the frequency of use) and HOW THEY ARE USED -- but cycling them alone, as some claim, isn't the only factor affecting spring life. It will also depend on how close to the spring's
elastic limits their regular use pushes them; science tells us that the closer to that elastic limit the springs are pushed, the greater the degradation they'll experience. As others have noted, that is a fact that is well supported by a lot of data.
danez71 made the following observation in one of the links cited earlier, with regard to the physics issue:
danez71 said:
Creep/sag/viscoelastic deformation.... call it what want. The fact is:
"All materials exhibit some viscoelastic response. In common metals such as steel or aluminum, as well as in quartz, at room temperature and at small strain, the behavior does not deviate much from linear elasticity. Synthetic polymers, wood, and human tissue as well as metals at high temperature display significant viscoelastic effects. In some applications, even a small viscoelastic response can be significant. To be complete, an analysis or design involving such materials must incorporate their viscoelastic behavior. Knowledge of the viscoelastic response of a material is based on measurement"
Until someone posts some actual verifiable evidence to the contrary.... there isnt any logical reason to doubt science.
danez71 cites other technical sources showing how springs can degrade over time, with use and when left compressed. Wolff Springs (in the FAQ area of their site) offers guidance on this matter, and they mention "elastic limits."
JohnKSa also cites a test of airgun springs that shows similar degradation.
Perhaps you can offer us some evidence to support your contrary position?
.