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Old April 8, 2013, 04:12 PM   #1
Dfariswheel
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Leaving an AR magazine loaded will damage it..RIGHT??

WRONG.
About 22 years ago I fully loaded a 30 round Okay Industries military surplus magazine and put it in my gun case with my old AR-15 Carbine, "just in case".

Today I took my new Colt M4 LE6920 to the range and decided the magazine had sat long enough if the spring was going to weaken or the lips spread, it would have happened by now.

It fired the entire 30 rounds perfectly with no problems at all. This leads me to believe that modern American made magazines don't deteriorate if left loaded long term.

The new Colt had only one stoppage, and that was a failure to fire. The round required some hard pulling to open the bolt, and there was no firing pin strike on the primer.
Re-chambered, it fired.
Since the round was an OLD reload, I wrote that one off to a slightly defective reload.
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Old April 8, 2013, 05:36 PM   #2
FrosSsT
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Compression and decompression wear the spring - not prolonged compression
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Old April 8, 2013, 06:51 PM   #3
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i had a bunch of GI mags loaded up for about 3 years and they started to form bulges on the base plate...i assumed that was from being loaded to long. but the springs were fine. what about P-mags? wouldnt the plastic eventually get brittle and break shooting all of your boo-lits on the ground/rifle?
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Old April 8, 2013, 06:55 PM   #4
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I once found a plastic magazine in a friends basement. it was fully loaded and had been so since before her husband passed away 10 years earlier. I loaded into my AR and didn't have a single hiccup.
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Old April 8, 2013, 07:40 PM   #5
JD0x0
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only if the rounds go off inside the magazine

Seriously, you're worrying about a spring in a magazine.. if it breaks in 60 years you pay $.40 cents for a new one
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Old April 8, 2013, 08:18 PM   #6
Technosavant
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The only potential issue is the tension causing the feed lips to spread apart. The spring will be fine, it's the weak body of the AR magazine design that becomes an issue.
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Old April 8, 2013, 08:44 PM   #7
mrvco
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Who started that silly rumor anyway?

I mean new car dealerships don't put their cars up on blocks until someone buys them...
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Old April 8, 2013, 10:34 PM   #8
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People just continue to hate on the ar because of its initial teething issues, which were no joke, but long resolved.
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Old April 9, 2013, 01:48 PM   #9
MarkCO
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The feedlips on aluminum AR mags spread due to impact, not spring tension!

Every round fired, the next round hits one of the feedlips, that is the wear cycle.
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Old April 10, 2013, 10:26 AM   #10
iraiam
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NO, the spring weakens with compression cycles. I have loaded AR and pistol magazines and left them stored that way for up to a few years, slap em - in fire them, and they are still like new.

I would also note that if you overload a magazine, the spring coils can be damaged and shorten its life span considerably, put in only the amount of rounds the mag was designed for. You can't overload many magazines, but there are some that are designed for 15 rounds and you can actually put 16 in, but you get the idea.
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Old April 11, 2013, 09:41 PM   #11
Ben Dover
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I consulted a colleague in the metallurgy depaqrtment about this issue more than twenty years ago.

His advice was to just leave it loaded.
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Old April 12, 2013, 07:23 AM   #12
Regolith
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Quote:
People just continue to hate on the ar because of its initial teething issues, which were no joke, but long resolved.

This is not an AR specific myth. People believe this about any type of magazine. I've also heard people worry about leaving guns with their hammers/strikers cocked or their bolts/slides locked open.
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Old April 12, 2013, 01:07 PM   #13
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In the 1970s, the Army taught us to only load 18rnds in the 20rnd mag and only 28 in the 30rnd one. This was because of concerns about "reliability".


Now, the Army (or the people in it) are s thought to be the experts but I have experienced the same kind of uninformed guidance there as one finds anywhere else. The main difference is that in the Army, you have to do it their way.

Leaving springs compressed leads to failure! That was basically true 100 years ago, especially when most gun springs were the flat type, which are most vulnerable to taking a "set". And it was true because knowing how to make a spring that wouldn't take a set, and actually doing it were much less common than today.

I have my grandfather's shotgun, bought new in 1909, and one of the advertised selling points was that its springs were guaranteed "never to take a set". Not just for the lifetime of the owner, never. And to this day, they never have. Sadly, the company backing the guarantee went away decades ago....

We know today that a properly made spring (and most are) does not weaken from being compressed and left compressed over a long time. IT is the cycles of compression/relaxation/compression that weakens a spring.

If a spring weakens only from being left compressed, its a "bad" spring. They do still happen, just not often these days.
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Old April 13, 2013, 04:31 AM   #14
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As a random aside, a Bren gun magazine will take 30 rounds, but you had to put 28 in as it did occasionally jam if you had 30 in...always wondered abut that. But no, as has been noted, compression per se does not "wear" a magazine. Seems a bit silly to have a loaded magazine lying around and not emptying it by fire though.
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Old April 13, 2013, 12:25 PM   #15
motorhead0922
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The spring will last indefinitely under full compression. As others have stated, it's cycling between empty and loaded that fatigues the spring. And fatigue life of steel is measured in 10's of thousands of cycles to over 10's of millions of cycles. You ain't gonna hurt it.

The feed lips of the mag don't actually get an impact when the gun fires. The cartridge hits the bottom of the bolt, not the lips, as the bolt strips the round above it forward into the chamber.

The only problem is with plastic mags, kept loaded, but not in the gun. Plastic creeps over time, spreading the lips. That's why Magpul PMags have a plastic clip on the bottom that can be put on the top when the mag is loaded, to keep the top cartridge off the lips, like they would be in the gun with the bolt forward.

Aluminum does not creep, so those mags can be loaded all the time, in or out of the gun.
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Old April 13, 2013, 06:47 PM   #16
Dfariswheel
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That's why Magpul PMags have a plastic clip on the bottom that can be put on the top when the mag is loaded, to keep the top cartridge off the lips, like they would be in the gun with the bolt forward.

Magpul says this isn't true. The cover is nothing more than to keep dust and dirt out. It puts no pressure on the cartridges.

For years we were assured by "experts" that aluminum AR magazines would spread the lips if left loaded, now disproved.
Now they're telling people that plastic mags will spread the lips if left loaded.
Top companies like Magpul say that too is not correct.
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Old April 15, 2013, 11:50 AM   #17
mdmtj
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Quote:
In the 1970s, the Army taught us to only load 18rnds in the 20rnd mag and only 28 in the 30rnd one. This was because of concerns about "reliability".
I was in the Army for 20 years beginning in the '70s. I was never taught anything like this and it certainly wasn't in any of the FMs or TMs.
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Old April 15, 2013, 07:50 PM   #18
Dfariswheel
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It wasn't in any manuals, but during the Vietnam War everyone "knew" that you had to download 20 round magazines to 18 rounds.

Some genuine multiple tour combat vets said that in their experience it was the truth, and in some units riflemen were ordered to download the 20 round mags.

Whether a 20 round mag needed to be downloaded to 18 rounds or not, it's rather difficult to argue with some guy with three tours under his belt as a combat infantryman or a Special Forces SOG vet when they tell you it's so.
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Old April 15, 2013, 10:46 PM   #19
D. Manley
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Re: Leaving an AR magazine loaded will damage it..RIGHT??

The only valid reason for downloading I know of is that some (but not all) GI style mags can be near impossible to seat with a closed bolt. I have also seen the floorplate blow off some fully loaded 30-rounders with a little rough treatment but who knows what really caused it to happen? It seems to me some GI mags have a little more substantial "ears" securing the floorplate than others. For mine that I have kept loaded I prefer PMags & use the feed ramp clip designed to relieve the pressure. I have read that Magpul has maintained fully loaded mags since they were first introduced and they still remain perfect today. They are also made with a smidgen of extra room to facilitate loading a full mag with a closed bolt.
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Old April 16, 2013, 10:10 AM   #20
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Even military instructors can stray from approved course curriculum and add their own antidotal opinions. I've seen it many times. I've even seen a typo in an air force training guide become gospel!
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Old April 19, 2013, 08:32 AM   #21
Skans
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I read on a very reputable internet blog that AR magazines only had a half-life of 15 years, and after that they quickly begin to decompose into toxic bauxite.:
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Old April 19, 2013, 09:27 AM   #22
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I don't think it will hurt, but i am not an expert.
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Old April 21, 2013, 10:15 AM   #23
Malamute
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I've left magazines laoded for many years, a few as long as 25 or so. They all seem to work fine.

When I messed with AR's years ago, I did notice it was easier to seat a magazine that was downloaded by a round or two when the bolt was closed. It helped also when hitting the bolt release to close the bolt on a fresh magazine. The gun would sometimes either close very slowly when cold and/or dirty, and a few times stopped. The bolt could be closed by pushing it shut with a thumb in the cutout on the side (pre-forward assist on commercial Colt AR's). Dowloading by a round or two helped noticably.
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Old April 21, 2013, 10:34 AM   #24
Alabama Shooter
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Quote:
In the 1970s, the Army taught us to only load 18rnds in the 20rnd mag and only 28 in the 30rnd one. This was because of concerns about "reliability".
From a casual shooting perspective this is not a problem.

From a military perspective it is a little different. In operations magazines will get filled with dirt and dust. If that works it's way into area between the first round and the feed lips it can lock it up tighter than drum. I have seen this many times when the soldier tries to chamber or reload and can not and then bangs the weapon on the ground to get it to load.


Putting fewer rounds in the magazine can help by reducing the tension on the spring. On the other hand this will cause the magazine to wear out slight faster due to the extra play in the magazine.


Most pros don't notice this problem because on a regular basis they unload their magazines and clean the mag and the rounds and then reload.
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Old April 21, 2013, 01:20 PM   #25
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I've left magazines laoded for many years, a few as long as 25 or so. They all seem to work fine.
I'm not trying to argue and I leave a bunch of my mags loaded. But I have seen magazines fail. For instance, I have a WWII M1 Carbine. I put the GI green sleeve on the buttstock that holds two magazines. Put two loaded GI 15 round magazines in that sleeve. (These mags looked brand new.) Left it that way for.... I don't know, 3-4 years. If I wanted to shoot the rifle, I just left those two mags there. I decided to fire them one day and took the rifle out in the pasture. Both mags failed. There would fire maybe half the mag and then just stop without raising the next round. It's like the mag spring wasn't long enough any more to push the carrier all the way to the top.

I threw them both away. And I don't keep my M1 Carbine mags loaded anymore. Maybe it is a design thing with that mag... I decided to "take the hint."

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