I just had a very unsettling problem at the range.  I took two of my kept loaded "go to" mags to the range to re-certify them and had at least 10 FTF's with each mag.  The mags are USGI with green followers and had been loaded with Lake City XM193 for six months. The FTF's ocurred with two different Bushmaster M4's, and my regular range mags worked perfectly in both rifles.  In every case the bolt would engage the round and drive it nose down into the front of the magazine causing a small amount of deformation of the bullet tip.  The cases seem to have a lot of oxidaton spots on them and they are a little rough to the touch.  I finished the session by loading one of the offending mags with a full load of Lake City from the same lot and did a flawless mag dump.  Thus my question, How long is too long to leave a magazine loaded?

Dilbert,

I didn't think that there was a "too long" time on mags. I've been wrong before and are probably wrong again but I don't THINK that there is any time limit on them. One would think that the longer the spring stayed compressed that it would loose it's "springyness" but I really don't think that is the case. As far as your "ready to go" mags being USGI, what are the other ones? If they're not USGI then I would think that it would be the mags and not how long you have had them loaded. I've got four of them and they have been loaded since April 1 and had not shot any until just a few weeks ago and I dumped all of them without any problems what so ever. It may also be that they had some oxidation on them as well making it not so smooth when firing the round and chuncking another one in it.

Maybe someone else can tell you different. I have made the comment that I learn something on this site every day.

First of all it sounds like improper storage due to the oxidation on the ammo. Second it sounds like the improper storage affected the mag as well. Check everything out before you make any decisions.

Sgt_Gold,  The mags where kept in the rifles at all times, except when the rifles went out to play and the mags didn'd.  They are stored inside a humidity and temperature controlled environment, but you may be onto something since the ammo from the same lot stored in a sealed ammo can didn't have the same level of oxidation.  Lake City ammo looks dirty from day one since they don't polish their brass so who knows ?!?  I pulled the mags apart when I got home and they were nice and clean and the springs don't show any signs of rust.  And just in case you are correct on point #2 I just ordered 5 NIW Labelle mags to replace the two bad ones!  Thanks for the response.

You can leave mag (or any other) springs under tension for approximately 11,000 years, twelve days, four hours, and thirty six minutes.

CYCLING the springs is what causes them to lose their tension.

I've succesfully fired 1911's that have had the mags loaded since D-Day!

Your problem lies somewhere else. That stuff should NOT oxidise.

Luck,

SD

i concur with sailordude, i was told by a spring manufacturer long ago "it's work that wears out a spring". the constant up and down causes them to weaken.

SailorDude hit that one on the head, springs, like any other metal fatigue when flexed. So long as your mags stay loaded or unloaded you'll be fine. It's when you load them, then unload them, then reload them that makes the spring get weak.  I'm sure there are rare cases of bad springs taking a set when the mags are left loaded over an extended period of time but this is the exception and not the rule.  If you're still troubled about this then do what I do and load down a few rounds.  I keep my 30rnd. mags loaded with 25 rounds.  I know it really doesn't matter but it gives my superstious side peace of mind.  Talk at ya'll later.  TN.Frank

i do the same, mainly to make it easier to load a mag with the bolt forward

The others are correct.  The spring in a fully loaded mag will last about as long as I will if you don't change the pressure on it.  It's the changes in pressure that wear out a mag spring.

I have to disagree, you can leave them loaded approximately 11,000 years, twelve days, four hours, and thirty four minutes, & 22 seconds.  Anything over that and your probably going to have to spend about 3$ to replace them..  

prosise

whew....5000 years to go before I gotta worry about it!

I had one of my P89 mags loaded with Golden Sabres in the glove box for like two years. Finally took it to the range to appropriately dispose of the ammo. [shock] Functioned fine, rounds went bang, and the only damage to the mag was a spot of rust on the floor plate.
[peep]

genius91

Be sure and check that you put in the spring back the right way.

Hey thanks for the responses guys!  Troy, do you happen to have a link to a good source for the Wolfe springs?  This has me in the mood to rebuild all of my mags.  Also I have been considering tumbelling some of my ammo for a short time to clean it up a little and maybe slow down the oxidation.  I know that you shouldn't over do tumbelling a finished round because it can break down the powder and cause overpressures.  Does anyone know how long I can safely tumble a finished round?  Until I can figure this out, my Rem 870 Combat has been promoted to chief home defender.  [:(]

Whack the mag so the rounds snug up against the rear of the mag. Sometimes during travel they move around in the mag, and can cause failures.
My next guess would be the spring.
-Steve

Georgia Precision had them in the EE under Magazines.  I was contemplating the same thing, just haven't got around to it.  I've got some older mags and I think they sell a kit with Perma-slik(?), Wolf replacement springs, and followers.

There was a thread on this topic awhile back.  Try a search.

I disagree w/ the consensus.  My AR mags are fine, but baretta mags do go to shit when loaded too long.