To load, or not to load, that is the question. Since the dawn of time, gun enthusiasts have debated whether it is safe to store your firearms magazine loaded. Today we will try to settle this debate. Spoiler alert, YES! You should leave your magazines loaded, but in the grand scheme of things, either choice will have negligible effects on the lifespan of your magazine spring.
A spring is a tool designed to store energy. The most important aspect behind the design of a spring is choosing the right material to construct the spring from. Ideally this material is high strength, has high elasticity, and is corrosion resistant. Music wire has become the industry standard when looking for these three properties. Dating back from use in pianos, it has shown the ability to remain consistently under pressure without shortening or stretching its unstressed form.
Now that the natural choice for our magazine springs has been chosen, let's take a look at the three main positions our spring will be in during use. In the “rest” state the spring is just existing in its coiled state not affected by outside forces. When you push down the spring, or in this example load the magazine, the spring is now in the “compression” state. This compression state is when the spring is considered to be at its peak stress point. Releasing the stress on the spring when firing a round from the magazine or unloading it is considered a “tension” state.
Spring failure is most commonly associated with REPEATED high stress, fatigue, and corrosion. When a spring is constantly in its compression phase and then released (loading and unloading magazines, cycling rounds) is when you will start running into issues. Repeated cycling of rounds or loading/unloading magazines is the culprit when it comes to magazine springs causing magazine malfunctions. The act of loading a magazine and unloading it is actually more damaging than just keeping the magazine loaded in the first place. However, failure from spring fatigue typically will only take place after the spring has cycled a million times through its rest, compression, and tension states, provided the spring was designed with the proper material for its use, typically music wire for magazines. Someone who shot their magazine over a million times, likely will need to replace most other firearm components before causing the spring to fail from fatigue. Corrosion is the least likely killer of your magazine spring. Unless you are a military operator who regularly is diving with your magazines, exposing them to salt water, dirt, etc, corrosion shouldn't be of great concern. Should you need to disassemble your Glock magazine for maintenance or upgrades, the Milspin Glock Removal Tool is an ideal tool for the job.
Ultimately, failure of your magazine spring will be caused by the repeated high stress of loading and unloading. Bringing our answer to a definitive yes, go ahead and keep your magazines loaded when not in use. By keeping your magazines loaded between shooting sessions, you are lowering the amount of times the magazine is under a high stress state.