Author Topic: How long do you keep a magazine loaded ?  (Read 1166 times)

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Offline Walt Sherrill

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Re: How long do you keep a magazine loaded ?
« Reply #15 on: March 10, 2018, 06:22:43 PM »
I'll repeat a point or two from my earlier posts, even though I seem to be arguing with people who have an almost religious belief in the eternal life of magazine springs.

There's no hard and fast rule about how long a magazine can be used or  kept loaded without damage --  it depends on the magazine design and how the magazine is USED!  Some mag springs may have the mechanical equivalent of eternal life.  Others don't live very long.

The famous 7-round 1911 magazine springs (the way JMB designed them) were far from fully compressed when fully loaded, and nowhere near the springs elastic limits.  Those mags/springs will continue to work for years, and cycle properly even if left fully loaded for those same years.   Try that with a new but very high-capacity magazine (like the 18+ rounders used in gun games) and you'll likely find some mag springs that fail far sooner than you'd expect.   The gun/spring designers are pushing those springs to do more with less material so that more rounds can be fit in a smaller-than-expected magazine body.   

Read the Wolff Springs FAQ -- you'll see that Wolff recommends downloading hi-cap mags a round or two when being stored loaded for long periods.  (They don't recommend that when you're carrying!)  Here's a link.  Pay attention to item 5.   https://www.gunsprings.com/index.php?page=FAQ

The Wolff recommendation to download a round or two is just a general rule intended to address a wide range of mags; you may not have to do this with some hi-cap mags.   Wolff also says that rotating mags can help -- but all that really does is spread the work (and potential wear) to other magazines.  The unloaded/unused mags don't HEAL when they're not being used, and IF you leave them fully loaded when they're stored (when they're out of the rotation), you've done nothing to prolong spring life.

The point is that compressing a spring is what can damage the spring.  Compressing the spring bends the material and can eventually cause it to break.  (The breaks typically take the form of very small micro-fractures in the materials, and when enough of the material has broken, the springs seem to get soft and are unable to do the work for which they were designed.  If you have a mag that lets the rounds nose-dive and not feed properly, for example, that's what's happened. 

Releasing a compressed spring doesn't increase the potential damage, it reduces it -- by taking pressure off the spring material and allowing it to return to its relaxed state.  (It IS a spring, after all!)  Cycling itself isn't the problem unless, when fully compressed, the spring it at or near it's design/elastic limits -- then it can begin to degrade.     

Offline Walt Sherrill

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Re: How long do you keep a magazine loaded ?
« Reply #16 on: March 11, 2018, 08:19:19 PM »
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.html

Most 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.html

Most 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.   
« Last Edit: March 11, 2018, 09:38:51 PM by Walt Sherrill »

Offline Walt Sherrill

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Re: How long do you keep a magazine loaded ?
« Reply #17 on: March 12, 2018, 12:35:10 PM »
boo2112:

Thanks for the extra links.  I've added them to my growing library of such links.  Most of them are above my pay grade, and I've only found one or two which address the STRESS of leaving a compression spring compressed at or near it's elastic limit -- which is the real subject I'm trying to get explained.  Most of these links are important in understanding how to design a spring to perform a particular function, but that doesn't help us understand the springs used at the edge of their design limits.

I posted the following link earlier, but I'll post it again, as it's worth a quick review.  Examples of hi-cap mag springs degrading (but still operating) after an extended period of being left fully loaded.   These springs are NOT cycled (except to be unloaded, tested/measured, and reloaded, once a month or so.)   I found it amazing that the Glock springs stand up so well -- but remember all the problems most folks have loading a new Glock mag, and it all makes sense.  Very stout springs.  The Ruger spring degrades more, but still continues to function.   His tests continue.

https://thefiringline.com/forums/showthread.php?p=6005156#post6005156

JohnKSa is an engineer, knowledgeable gun enthusiast and  airgun enthusiast familiar with the springs used in air guns; he has frequently posted links to sources from that community -- where springs are still the power source of choice for aimed fire.    He addresses the topic directly.