Warp said:
Because I know the properties of the springs/materials and have looked into this subject multiple times. Cycling the springs is what wears them, not keeping them loaded...
Provided the magazine is a proper design that does not over compress the spring, your main concern for spring wear is cycling, not keeping it loaded.
You're speaking from authority in the first paragraph above, i.e., you offer no evidence or data to support that argument. You imply that we should just believe you because know what you're talking about and you've done your research. Some of us have done our homework, too, and apparently have taken it a bit farther than you have. Some of us would also like some evidence. You offer only your testimony.
Can you offer us a theoretical explanation as to why what you say is true? Can you tell us why cycling damages a spring! Will loading a magazine with fewer rounds make a difference in the spring's life? If so, why? If not, why not? That spring is still going to cycle if it's working with 10 rounds or 15 or 17... (and some guns use the same spring for all three mag sizes.)
I suspect that you're a 1911 enthusiast, and if so, your base of experience is much different than those here who use 17-21 9mm round mags 15+ round .40 mags, or 14 round .45 mags. If your entire base of experience 3-4 mags used over a decade, limited to 1911 mags, those mags, by design, aren't stressed that much when fully loaded and certainly don't get compressed particularly far when being cycled. And if you don't store them loaded, you have no basis for making a judgment... You've only cycled them. If you do store mags loaded, try it with hi-cap mags and check back with us!
This topic
has been discussed here and on
The Firing Line at length, with technical references and explanations offered.
In the past year or two, the participants have included a metallurgist or two as well as engineers form the aerospace industry, where metals are a critical factor (especially when talking about jet engines). They disagree with you. I'd argue that you've got it partly right, but that you are ignoring a key factor: a spring's elastic limit.
If you don't over-compress those mag springs -- your disclaimer above -- cycling is not going to be a big issue, either. Cycling matters most when you push the springs near to or beyond the spring's elastic limits. That's why some 1911 7-round mag springs will seem to last forever, and that's why you'll likely have different results with hi-cap mags (holding 17-20 9mm rounds, or 15+ .40 rounds). I suspect you'll get different results with the double-stack 1911-like guns used in IPSC than with those 7-round 1911 mags. Long-term, deep spring compression is why Wolff Springs recommends downloading hi-cap mags a round or two for long-term storage. (If they were soley intent upon selling more springs, they would just keep their mouths shut!!)
You also speak about "
proper [mag] design."
What is proper design? Is it a mag that holds 10 rounds and has a spring that almost lasts forever, or one that holds 20 rounds, but has to have the spring replaced periodically?
The correct answer depends on what the mag and gun were designed to do, doesn't it? Longer spring life isn't always a gun designer's key objective, nowadays. A properly designed mag and spring that is used in IPSC is different than a properly designed mag and spring used in a 1911 mag carried by a Army MP during WWII or in the Vietnam War.
Many of the engineers and specialists who work with or have studied the materials in question and who have participated here say that compressing and releasing a spring
alone isn't all that matters, but HOW FAR the spring is compressed when its cycling! If the spring is compressed to or beyond the spring's elastic (design) limits, the spring's metal will slowly develop micro-fractures, and as those fractures occur, that part of the metal loses its ability to do work. That means that the work must be done by the surrounding material. That extra work done by less metal will eventually lead to more fractures. The cycle repeats and the damaged area expands and will eventually lead to failure. If you don't compress the spring deeply (if you never load a 17 or 21 round mag with more than 15 rounds), the micro-fractures may never occur, or will occur so slowly that the spring can last a long, long time With coil springs, these fractures will eventually make the springs appear to soften (and not do the job) and they'll often be tossed before they break. With leaf springs, the spring's work is confined to a narrower area in the spring metal, and those springs will often break before the soften too much to be useful.
I asked this before -- maybe you can give us an answer, since you're familiar with the subject:
If cycling is what wears out springs, why do tappets springs in a car engine, which will sometime cycle hundreds of millions of times over an engine's life, almost never fail. Or why does a Rorhbaugh R9 recoil spring have a projected life of only 250 rounds when the recoil springs in most full-size guns may last 5,000 - 6,000 cycles, or more?
Cycling does matters, but so does the depth of spring compression. It's DEEP COMPRESSION that wears the spring out (
if, at that deepest point, the spring is pushed to or beyond it's elastic limits). Some new gun and mag designs DO THAT --
because it's the only way to get the gun or mag to function as intended. (The RorhbaughR9 was very small, and needed a small recoil spring.) The mag springs in some of the hi-cap mags are the same springs used in 10 or 15 round mags. Which do you think lasts longer? A 17-round mag doesn't cycle as often as a 10-round mag using the same spring, but which must compress a lot farther? A 7-round 1911 mag has a lot of reserve power (and space) under the follower when fully loaded...
IF the spring is held at that point of deep compression, and that point is near or beyond the spring's elastic limit (as might be the case with a 18-round high cap mag stored fully loaded), it will cause as much or more spring wear as cycling. That type of damage seldom occurs with 1911 mags -- even the 8-rounders or with full-size double-stack guns running non-high capacity mags -- because the springs aren't compressed as far. (Maybe Wilson's new design prevents over-compression... but that may be like gilding the lily, since 1911 mags aren't that likely to suffer from the spring failures seen in many high-cap mags.)
Concern about over-compression is why Wolff Springs recommends downloading hi-cap mags a round or two for long-term storage in the FAQ page. Many such springs are, by design, pushed to the limit. Springs, as noted earlier, are increasingly renewable resources: with some gun and mag designs, the springs need to be pushed hard for the gun to perform as intended. Wolff doesn't recommend downloading for 1911 mags.
Here's some of the technical info posted in earlier discussions by
danez71. He posted a number of others links, too, but that was several years ago and most of the links to industry sites no longer work because those industry sites frequently change. I wish the other links, not posted, still worked, as they offered very good examples of how different materials, including metals used in springs, deteriorate under stress -- and explained what things cause stress.
http://en.wikipedia.org/wiki/Elasticity_(physics)
http://en.wikipedia.org/wiki/Plasticity_(physics)
http://en.wikipedia.org/wiki/Viscoelasticity
http://en.wikipedia.org/wiki/Creep (deformation)
Just a snippet taken from
http://en.wikipedia.org/wiki/Viscoelasticity:
"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"
