I have noticed a few threads talking about worn out springs on ARs and there is a lot of argument about what cause springs to weaken.  This includes magazine springs and trigger springs.  Folks weight in with personal experience like "we drew our rifles from the armory and they had the hammers cocked and when we pulled the trigger, the hammer barely tapped the primer....so you should always store the gun empty with the hammer down."  Others are like "make sure you cycle your mags to relax the springs every once in a while or they'll weaken and you will have failures to feed."

Eventually, an engineering-type will weigh in and often discount they above causes of metal fatigue and state that such fatigue is only caused by the spring being used...ie: compressed and relaxed a number of times.

I thought I would share some things I noticed recently.

Glock mags:  I originally had 2 magazines for my Glock 27 that I put the + floorplate on.  It makes them 11 round mags instead of 9, but that last round just BARELY...and I mean BARELY, gets in there.  The spring is literally, fully compressed in the magazine body.  I have been using these mags for some 4 years and after a year or two, I noticed that it had become easier to get that last round in.  About two years, I got a third magazine.  I have almost exclusively used just the original two for shooting.  The third has sat, loaded and ready, but not used, for 2 years, and that 11th round still just BARELY gets in there, just like new.  To my knowledge, Glock has not changed the metal content of their mag springs over this time period.

Ballpoint pens:  I use click-top ballpoint pens at work.  I keep a pair in my shirt pocket.  One day, one broke, so I got a new package of 2 new pens.  I put one in my pocket to replace the broken one and put the second aside in case I have another FTW (Failure To Write).  The first time I used the new pen, I noticed that the clicky-action was stiffer than the old one.  After a few months of usage, I could no longer tell the difference between the two pens' clicky actions.  Curious, I went to the pen that I had put aside, and it still had a nice stiff action spring in it.  The pens were all stored the same, with the writing tip retracted, but the ones that got cycled, weakened.  The one that stayed still, did not.


Based on those observations, I think I have to agree with the materials engineers (I know, shocking).  These springs are not weakening and failing due to being stored compressed.  They are doing so from being used.


$.02 added.