question about the spring in the magazine

[FuziDave]

Ok I have a question being a newbi ;)

Growing up, we always had revolvers. But now I have a Berretta 92FS and a Bersa Thunder 380. Both of which use a magazine. With a revolver you can leave it loaded indefinitely. But since these use a magazine, and a magazine has a spring, and you obviously need to have some bullets in the magazine to make the gun usable.

I would think you’d want to “exercise” the spring now and again, but as hard and expensive as it is to find ammo, I’m just not using it all that much. And in my mind, a fully compressed spring over time will loose some of it’s strength.

My question is how long can you have a loaded magazine’s spring compressed before you need to "relax" it?

[DoubleJ]

I would think you’d want to “exercise” the spring now and again, but as hard and expensive as it is to find ammo, I’m just not using it all that much. And in my mind, a fully compressed spring over time will loose some of it’s strength.

My question is how long can you have a loaded magazine’s spring compressed before you need to "relax" it?

nope.
as to your question, 30, maybe 40 years. probably more.
the point is that you don't need to worry about "relaxing" the spring. either compressed, or not, the spring retains it's strength.
exercising the spring is actually what "wears out" the spring. this would take thousands of instances before strength would be reduced.

all of this info I have gleaned from this site, from our various experts, with a nod to G.C. Montgomery.

[BobCat]

A properly designed and fabricated spring will not "loose strength" or take a set while compressed to it's maximum design compression, at any temperature it is likely to see. If you compress it and take it to 800-1,000ºF it will experience what is known as creep deformation - it will yield and take a set.

Cyclic loading initiates and grows fatigue cracks. Each time you load the magazine and unload it, you put one cycle on the spring. I have never seen a magazine spring that failed by fatigue - it takes thousands of cycles to initiate a fatigue crack, and thousands to millions of cycles to grow it until the part breaks - depending on the stress, and whether it is revered or not. (If you repeatedly unloaded the mag and then stretched the spring before re-loading it, that would be worse than just loading and unloading it).

Sorry to babble endlessly. With a properly designed and fabricated mag, do not worry about leaving it loaded for a long time.

Regards,
Andrew

[Keith B]

A properly designed and fabricated spring will not "loose strength" or take a set while compressed to it's maximum design compression, at any temperature it is likely to see. If you compress it and take it to 800-1,000ºF it will experience what is known as creep deformation - it will yield and take a set.

Cyclic loading initiates and grows fatigue cracks. Each time you load the magazine and unload it, you put one cycle on the spring. I have never seen a magazine spring that failed by fatigue - it takes thousands of cycles to initiate a fatigue crack, and thousands to millions of cycles to grow it until the part breaks - depending on the stress, and whether it is revered or not. (If you repeatedly unloaded the mag and then stretched the spring before re-loading it, that would be worse than just loading and unloading it).

Sorry to babble endlessly. With a properly designed and fabricated mag, do not worry about leaving it loaded for a long time.

Regards,
Andrew

BobCat, you wouldn't happen to be an engineer would you??

Seriously, good information. I have seen fully loaded magazines that have sit for 8-9 years and still have just as much life left in them as ones with new springs.

[FuziDave]

good to know, thanks.

and i did understand all that engineery stuff too

[bdickens]

What BobCat said.

[AEA]

What everybody said!

[NTexas_V-Star]

Is this also true for AR mags?

My boss and I have this arguement, and I always mirror the statements made by others on this thread....that the only real damage done to the spring is by constantly loading/unloading it. He maintains that he only keeps 27 rounds per mag to keep the spring from wearing out. Is this something that really makes a difference? Or is it just a personal quirk?

[Mithras61]

Is this also true for AR mags?

My boss and I have this arguement, and I always mirror the statements made by others on this thread....that the only real damage done to the spring is by constantly loading/unloading it. He maintains that he only keeps 27 rounds per mag to keep the spring from wearing out. Is this something that really makes a difference? Or is it just a personal quirk?

He probably acquired that habit in the military. I remember the magazines they gave us for range work back in '79-'85 had springs that were so worn they could only lift about a half-magazine of rounds. Any more in the magazine meant constant mis-feeds and jams.

[BobCat]

Keith B,

Yes, you nailed it.

Debated about posting this but what the heck: anyone interested in metals ought to download MIL-HDBK-5J at http://femci.gsfc.nasa.gov/links.html" onclick="window.open(this.href);return false; - it is really worthwhile. It is a big zip file, but if you have fast internet it only takes a minute. And y'all paid for this already - your tax dollars at work. There is enough introductory stuff to make the rest at least comprehensible.

My nefarious purpose here is that I think the Forum membership includes a number of college students. If I can get one smart young person interested in metallurgy or materials science, that's the jackpot. If other folks just get some amusement or a few questions answered, that's gravy.

Have fun!

Regards,
Andrew
http://tinyurl.com/lxhte6" onclick="window.open(this.href);return false;

[MoJo]

Is this also true for AR mags?

My boss and I have this arguement, and I always mirror the statements made by others on this thread....that the only real damage done to the spring is by constantly loading/unloading it. He maintains that he only keeps 27 rounds per mag to keep the spring from wearing out. Is this something that really makes a difference? Or is it just a personal quirk?

The reason for downloading AR mags has nothing to do with the springs it's to keep the feed lips on the magazine from deforming. The aluminum that the majority of AR mags is made from will spread under the pressure of a fully loaded magazine. I download any AR mag that is going to be stored loaded but at the range I'll fill 'em up! I don't know how well the polymer magazines and the steel magazines feed lips hold up. I would think the steel may be more durable and the polymer at least as good as aluminum.

[One Shot]

Some would recommend not filling a spare magazine for another reason.
The difficulty of seating a full magazine in your pistol on a closed slide, particularly in a stress situation.
At least someting to practice.

[dukalmighty]

A properly designed and fabricated spring will not "loose strength" or take a set while compressed to it's maximum design compression, at any temperature it is likely to see. If you compress it and take it to 800-1,000ºF it will experience what is known as creep deformation - it will yield and take a set.

Cyclic loading initiates and grows fatigue cracks. Each time you load the magazine and unload it, you put one cycle on the spring. I have never seen a magazine spring that failed by fatigue - it takes thousands of cycles to initiate a fatigue crack, and thousands to millions of cycles to grow it until the part breaks - depending on the stress, and whether it is revered or not. (If you repeatedly unloaded the mag and then stretched the spring before re-loading it, that would be worse than just loading and unloading it).

Sorry to babble endlessly. With a properly designed and fabricated mag, do not worry about leaving it loaded for a long time.

Regards,
Andrew

I see somebody stayed at the Holiday Inn Express at least once

[BobCat]

I see somebody stayed at the Holiday Inn Express at least once

Had to google the phrase "stayed at the Holiday Inn Express" to understand your comment. I don't watch much TV, never saw the ad, and certainly never stayed there.