So I have a hand gun always by my bed and keep the magazine always filled, every week or so I will take the ammo out and let the magazine "rest" for a day before putting ammo all back in it. Is it bad to leave ammo in the magazine? Am I wearing the spring out?

No it isn't bad to keep ammo on the mag. The springs wears from being repeatedly compressed and decompressed.

 

 

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I have always heard no in response to this question. Physics-type people have told me that loading and unloading stresses springs, not being continually loaded.

The spring gets worn with cycling.....when you load and shoot or load and unload.

If you are worried about this buy a spare mag or two and rotate them every couple of months.

Cool thanks guys!

What is a worry, is if you keep loading the same ammo into the chamber. Ie unload SD ammo, take gun to range shoot plinker ammo, take gun home, reload same SD ammo. You can get bullet set back after multiple chamberings. Set back = over pressure.

Watched a video a long time ago where a guy did an experiment on this. Kept a mag loaded for a couple years then opened them and compared the spring to a new one. Spring did not wear out. Like most have said already, IMO the spring wears out from use [loading and unloading].

I have always heard no in response to this question. Physics-type people have told me that loading and unloading stresses springs, not being continually loaded.

That's an ideal spring Springs tend to wear out under fatigue in the model. But metals do creep as well (strain under a continuous load). Springs generally resist this fairly well but not everything does. Some mags tend to have other issues such as widened or even split feedlips when left loaded a long time. Briefly unloading them from time to time would not help since they would still remain under load about the same amount of time and you have simply added some fatigue to the mix. So it really doesn't matter. Most modern self defense magazines don't suffer from these phenomenon noticeably but I have seen it as have others. I have AR-15/22 mags that lost a lot of force from being left loaded, Sten mags that had feed angles changed by being left loaded, and a Ruger 10-22 rotary magazine that stopped working after being left loaded. A person I know indicates AR magazine feedlips can spread slightly from being left loaded causing multifeeds, but it is my understanding this is rarely a problem and I don't worry about it.

if the spring is designed properly, a loaded magazine won't stress it beyond it's elastic limit - the range where it will return to normal.  Repeated loading can cause fatigue failures but you typically see fatigue failures with very high loads or many, many thousands of cycles.

 

I have a pistol that has had a magazine loaded continuously for 23 years with no problems.

 

Even if it does wear out in year 30, magazines are cheap.

if the spring is designed properly, a loaded magazine won't stress it beyond it's elastic limit - the range where it will return to normal. Repeated loading can cause fatigue failures but you typically see fatigue failures with very high loads or many, many thousands of cycles.

 

I have a pistol that has had a magazine loaded continuously for 23 years with no problems.

 

Even if it does wear out in year 30, magazines are cheap.

Replacement mag springs are even cheaper.

Loaded mags are a great way to store ammo. Funny story but the last time ATF was out here, one of the IOIs commented on how many loaded mags and nutsacks were on the shelves. I said, "It's the most efficient way to store ammo I've found to date." He asked about weakening the springs and I explained that springs wear when cycled and used a paper clip as an example (it's fine until you start repeatedly bending it).

paper clip model is a good example. I'm stealing that.

 

as others have said, it's movement that wears them out, assuming you're not stressing the spring beyond its limit which a properly made magazine won't do. interesting anecdote about that: people complain about HK's P30 mags only being 15 rounds and have noted you could trim the follower to get 16 or even 17 rounds in the mag. HK has (unofficially) stated in the past the reason they don't is it can compress the spring beyond it's reliablity, causing it to wear out past their desired lifetime. (there's also the factor of reliability of the follower to move properly in the mag body. trimming it can result in the follower tilting inappropriately, causing a feed error.) 15 rounds in a mag that size with a specific reliability rating for the spring would up being the conjunction of all factors for them.

paper clip model is a good example. I'm stealing that.

 

 

 

Or you could remember that all those old cars you find sitting out in the woods or a junkyard after 60 years sitting there on collapsed springs, oh, wait, that's right, they've been loaded for 60+ years and still bounce like they did in the 50s.