Some folks say that leaving a pistol or rifle magazine loaded over long periods makes no difference and causes no harm.
Some folks say to unload a couple of rounds occasionally, others to unload them completely and to rotate loaded and unloaded ones.
Some folks say that it the cycling, or number of times the magazine is loaded and unloaded, that makes the difference.
I have read some explain that car suspension springs and valve springs are under much more strenuous duty, and don't loose their tension. These statements are totally wrong, as I have had to replace coil springs on two vehicles and have another one at this time that is due for coil spring replacement. Also, it is well-known to hotrodders (an activity in which I've dabbled a bit) will replace valve springs in older engines when performing a rebuild where peak rpm will test the spring's ability to ensure that the valve train follows the cam profile. Therefore, I discount these analogies because I know those making them are not correct.
I have read people claim that Colt 1911 magazines have been left loaded for amazing periods of time, and that the magazines still function afterwards.
I have heard it said that Smith & Wesson says that leaving a magazine filled is no problem, but that they tell Law Enforcement armorers to change magazine springs every 5 years or 5000 rounds.
Of all of the explanations on this and the opinions expressed on internet forums, this one comes closest to what I think is true:
I put the question to an expert,my son,who has a Masters Degree in Metals and Materials Engineering from Colorado School of Mines . He started talking molecular structure,.............I said whoa ,simple words for your simple old man please, the answer..yes ..and no..springs will "relax" if left in a constant state of "tension" it may be a fraction of a percent or 5-10% depending on material,treatment,temperature,stress..........but that springs could be treated to lessen the degree of "set" .A fully loaded spring will relax more than one half loaded because it is held at a higher stress level so if you leave a magazine fully loaded for a year or two it will still work,just the last round or two might feed a little sluggish
(from
http://www.nationalgunforum.com/semi-au ... zines.html)
With this all said, this is my take:
The greatest determining factor in this matter is the steel used in the spring and the heat treatment that is applied to it.
A good quality spring, such as those made by Colt, will last for quite some time. However, I have seen aftermarket 1911 magazines fail because of the springs loosing tension. I have also experienced failures to feed due to weak magazine springs in two magazines of one of my own pistols.
I think that one is probably safe keeping a magazine loaded, when that magazine has a quality spring. The real rub is, what is a "quality spring"? When you consider the firearm you intend to keep with a full magazine, are you satisfied that it is made with quality materials and that the processes of manufacture exhibit a high level of quality control? It is one matter when the failure of a magazine spring is used for sporting purposes, and another when the magazine in question is part of a system that must be instantly ready for use. In the first case, failure of the spring is a statistical data point. In the second, it could be a disaster. The USA is very litigious, and gun makers are usually pretty careful to put things on the market that are safe, even when they know idiots are going to use them. This is not something that can be trusted 100%, but as a tendency, I think it is true. Manufacturers in other countries are another matter. For instance, some Japanese and Belgian guns are of the very highest quality, while others are junk.
Now, a spring is a spring, even though they come in many forms, such as a leaf spring, torsion bar, or a coil spring (which is a torsion bar wound into a circular or spiral form). Revolvers have springs and are widely regarded as being more reliable in a self-defense situation. Of course, they are not usually kept ready with their springs under peak tension. Likewise, double shotguns are normally not stored when cocked. (I keep snap caps in my old LC Smith and never leave the internal hammers cocked.)
I think it should be recognized that spring technology has come a long way, with the rest of metallurgical science, and that gun springs, which were somewhat of a black art 100 years ago, are pretty much a known practice today.
My own choice is to never leave my magazines full over long periods of time, such as when they are in storage.
I would say that, if one has a modern gun of known quality, it is probably safe to leave the magazine loaded.
I would agree that compression cycling of the spring may well affect spring tension over the longer term, compared to leaving a magazine loaded.
I am not an expert on anything but my own opinions. But what do I suggest? Since the choice of others in this matter isn't something that impacts me, I suggest that each person research the subject sufficiently to make them comfortable with their conclusions, and then to act accordingly. That's what I've done.