is it bad to leave a mag loaded?

On a quality magazine, it would take years of being fully loaded to render it unusable.  Personally, for long term readiness, I download mine a few rounds.
I think it would be much worse if you ever needed it, being unloaded.
www.gunsprings.com , FAQ #6 answers your question and more.

If you just replace your mag springs yearly you won't have to worry about it.

I have had a usp 45 for 5 years.  My mags were loaded 80% of the time and I have fired over 6,500 rounds.  I just had to replace the mag springs, but there is no damage to the mags.

I have a mag for my Browning Hi-Power that has been loaded since 1973, and it still works fine.
I've only unloaded and loaded it half a dozen times in all that time.
I've always heard that a mag can stay loaded, almost indefinitely, with little or no harm. It's the number of times the spring has been compressed that will cause fatigue.

At Glock Armorers School they taught us that if you unload the mag at least once per 6 months and leave it unloaded for as long as it takes to clean the weapon you should be good indefinitely.

I always keep my 45 mags loaded 'cause I might need 'em

Never had any problems keeping them loaded.

Any USGI or quality spring can stay compressed (loaded) indefinately without failure. As stated earlier, is the number of compressions that weakens the spring.

There is no reason, none what so ever, to download your mags. The money spent on changing springs yearly would be much better used on ammo. Unless you shoot thousands and thousands of rounds per year, all in the same mag.




Cody @ Magazine Specialties

I've kept the mags for my Sig P239 loaded almost all the time in the 3 years I've had it.  Never had a problem with them while flying through ammo at the range.  As long as they're cycled regularly and checked for function, you shouldn't have a problem.  

I always take my springs out, put them quickly in a warm diaper for their comfort. Then I soak them gently for 2.37 hours in some light cooking oil. After I dry them off, I do an incantation recalling the spirits of Incan gods then reinstall them in the mag body, careful to not to look at them, for fear it will weaken their souls.

I heard it at a gun show and it seems to work, so why mess with success?

Quoted: I always take my springs out, put them quickly in a warm diaper for their comfort.

Will "Huggies" work here??

I kept the mags for my Sig P220 fully loaded for about 5 years (except while they were actually being used) and never had a problem.

For one reason or another, I decided to worry about it and bought a whole new set of mags and let the old batch "rest". They've been resting for two years now, and the new set is always loaded and never had a problem.

I have only original Sig mags and some MecGars.  I guess I could load up the old mags too, but it gets unwieldy carrying 14 mags around - I've only got so many pockets, ya know. :)

I am presuming that this could also apply to 20 or 30 rd Ar-15 mags?

  Want greater peace of mind? Use a revolver (yeah, I know, revolvers have little springs in them too, but at least no mag. or mag. spring.)

  That different gunwriters, experts , gun and mag. manufacturers, and ordinary shooters say quite different things about mag. springs (only a few of which are in this thread)  shows that there is simply a lot of uncertainty about these "how should you treat them"/"how long do they last" questions. One gun website, for instance, states that magazines should be disassembled, and their springs removed and cleaned and reinserted, everytime the gun is cleaned.

    You just have to take the chance that something will go wrong the mag. spring/mag. case/lips/recoil spring/extractor/whatever.

    Revolvers can screw up too, but less often.