Load magazines to 80% of capacity to prevent spring fatique


Alan Fud
May 5, 2004, 10:12 PM
Since this applies to both pistols & rifles, I thought it should go here

Couldn't sleep the other night so I watched some shows that I recorded earlier. Must haved made a mistake on the recorded because I apparently either recorded the wrong channel or the wrong time for one of the shows and ended up recording some show on the History Channel having to do with the M16. What I did record was pretty interesting and I wish I would have caught the whole thing.


There was a segment with an individual who worked with "the greatest gun inventor since John Browning" and it was said that magazines should be loaded to 80% of their capacity to prevent spring fatique. It was said that troops with 20 round mags were told to load it with only 16 rounds.

While I normally download by a round, this was the first time I heard of this "80% rule". Have other members heard of this or seen the show? Does anyone else follow this 80% rule?

This would mean my Para P14.45 should be loaded with (11+1) rounds instead of the (13+1) rounds that I now keep in it. My 4013TSW should be loaded with (7+1) instead of the (8+1) that I keep in it.

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May 5, 2004, 10:22 PM
Never heard that before. I always load my magazines to full capacity and have never had a spring fatigue problem. I believe that alot of times if you are having that problem the springs are bad to begin with. You also hear stories from time to time of downloaded dropped guns or magazines in which the rounds juggle around and stovepipe. Not good.

May 5, 2004, 10:31 PM
All mine are full, too, even the ones that sit till my next range trip or longer.

Dave R
May 5, 2004, 10:31 PM
It depends on the mag. A properly designed mag takes its spring's compressability into account and allows loading to full capacity. This generally means a follower deep enough to hold the compressed (but not over-compressed) spring. There are some fairly well documented cases of 1911 mags loaded to full capacity for decades and still functioning properly.

From what I hear, it WAS common practice to download the 20 rnd M-16 mags, both to save the spring and to prevent misfeeds when fully loaded. But I also hear that the M-16 mags were considered semi-disposable.

May 5, 2004, 10:53 PM
From what I understand, when you store magazines full of rounds for extensive periods of time, it would be a good practice to rotate them and let the ones that were under compression for so long rest a while. While this may be a good habit, it probably isn't necessary... If you ask me, a good magazine should be able to hold a full load continuously for years with no failure, or else it's not a good magazine.


May 5, 2004, 11:03 PM
Do double stack magazines have more trouble with this than single stack?

Cameron Lamont
May 5, 2004, 11:07 PM
I have magazines that have been loaded to capacity for years (my H&K Compact has four magazines that have been only unloaded for the length of time it took to load them again, I have had them for 6 years now).

Others have mentioned that it is the actual movement that reduces a springs capacity. So the magazine left loaded for years will actually retain its power longer than the magazine that is loaded and unloaded constantly.


May 5, 2004, 11:10 PM
rotate them and let the ones that were under compression for so long rest a while.

It's not a mule. Magazines don't need a "rest".

Standing Wolf
May 5, 2004, 11:10 PM
It's quite a little bit less risky simply to replace magazine springs every five or ten years than wander around armed to partial capacity.

May 5, 2004, 11:14 PM
Hmm... it just seems that springs tend to lose compression and elasticity when compressed or stretched for long periods of time. I guess if they're high quality they should always return to standard compression though, even after a being loaded up for a long time.

May 5, 2004, 11:31 PM
Agree with Standing Wolf.
I keep all mags topped off, inspect and replace springs as need.

On TFL there was a number of threads on this. Concensus - the spring doing work caused more fatigue.[ Loading / unloading ]

I have some mags, single and double been loaded for years. Have kept Shotguns loaded for years. No problem here.

May 5, 2004, 11:32 PM
I know of some of my fellow Marines who swear that you HAVE to load only 28 rounds into our 30 round mags, otherwise they may cause failures. Myself, I always load to full capacity, and when going to condition 1, I always replace the mag that I chambered a round from with a full mag. Never had a single problem...

May 6, 2004, 12:33 AM
I only single load my semi autos to prevent failures.:rolleyes:

When do the myths end?

May 6, 2004, 12:42 AM
If you are handed a worn out M16A1 or A2, with a pile of old mags that have an unknown number of rounds threw them, you may have to download the magazine because nobody bothered to chang the spring 20,000rds ago.

May 6, 2004, 12:57 AM
If you are handed a worn out M16A1 or A2, with a pile of old mags that have an unknown number of rounds threw them, you may have to download the magazine because nobody bothered to chang the spring 20,000rds ago.

Not to mention they were built by the lowest bidder.

I always fully load my magazines, chamber a round, then top off. Never had any problems and I don't figure there's any sense going into a gunfight with less than I could reliably have.

4v50 Gary
May 6, 2004, 01:00 AM
The only time I've ever heard of reducing a load for long term "storage" is from Remington with respects to their extended shotgun magazine. Other than that, I've always kept my magazines fully loaded.

May 6, 2004, 04:51 AM
With pistols I top off so I have 10+1 on tap. With FAL's however, I only put 19 in the mag. Once every range session with full mags, the bolt will fail to go all the way into battery due to the difficulty of stripping the first round off a full twenty rounder. Downloaded to 19 it runs flawlessly. Fatigue? Never been a concern of mine.


Marko Kloos
May 6, 2004, 05:51 AM
Springs wear from repeated compression and decompression, not from being compressed for a long period of time. Once a magazine is loaded to capacity for a second, it may as well be loaded for a year or ten, from a metallurgical standpoint.

I load my mags to full capacity, keep the carry mags loaded all the time, and invest $16 into a set of new +5% springs from Wolff every two years or so.

May 6, 2004, 07:05 AM
The myth continues , it will not die.

May 6, 2004, 07:09 AM
This topic AGAIN? :barf:

Just read this thread from less than 3 weeks ago. (http://www.thehighroad.org/showthread.php?s=&threadid=76303)
If you still don't get it, then do a search in the Rifle Country forum. It gets brought up a LOT over there.

Zach S
May 6, 2004, 08:00 AM
I cant recall how much they are, but IMO, magsprings are cheap. If it holds 7, 8, 14, or 17 rounds, thats how many I'm putting in.

The only thing I download is my Thompson mags. I probably wouldnt if they made 30 or 60 round boxes. That will probably change when I start reloading though (partial boxes get on my nerves for some reason I cant explain because I dont get it myself).

Ben Shepherd
May 6, 2004, 08:26 AM
A liitle side trip here. I've built A LOT of engines over the years. I've never yet loosened rocker arms on an engine to decompress valve springs for storage. Never had problems. But on an engine we ran at 8,000 rpm for a 100 mile road race(love Nevada:D) those springs were done.

Our moderator has it: It is cycling springs that fatigues them. As long as it is properly designed it doesn't care which end of its range it's in.

john l
May 6, 2004, 10:22 AM
The only problems that I have ever had with glocks have been two used ones that I bought at different times. Both of the previous owners had all their mags (all high caps) completely loaded to capacity for who knows how many years. I had fails to feed with both of them. I got new springs and the problems went away. No one can convince me that magazine springs don't lose their horsepower. I once heard that if you download your magazine even by 2 rounds, you decrease the "load" on that spring by 50%. Now, I believe that to a certain extent. But I am not an engineer, so I can't know if it is 100% true.
I feel more comfortable having my pistol mags downloaded by one. If others deride that practice, then so be it. I am a sum of my experiences.
john l

May 6, 2004, 01:10 PM
well you can't beat physics ;)

May 6, 2004, 01:16 PM
With the right material, a spring shouldn't degrade appreciably when left compressed.

There is a phenomenon called creep which would effect springs that are loaded for prolonged periods at elevated temps that would result in the spring relaxing. Again, shouldn't be a problem with quality parts.

May 6, 2004, 01:27 PM
No one can convince me that magazine springs don't lose their horsepower

chances are, you'll wear out a magazine faster by loading it and then unloading and rotating then just leaving it loaded.

Use causes mags to wear out. If the parts are highquality and you can't over compress it, etc they'll be just fine.

If you use them everyday, well of course eventuall they'll lose their strength

P5 Guy
May 6, 2004, 10:38 PM
WW II vet lived behind me about seven years ago. Nice guy, we were talking about guns and he says he has his 1911 from the war. So, we go to the range and find, causes much RO yelling, the mag is still loaded?
Well he racks it and fires seven shots of 1944 45ACP that had been, he says in the gun since he got home in '46!
Maybe springs and ammo were better back then?

Ukraine Train
May 7, 2004, 12:44 AM
I asked my materials prof about this, who's a materials scientist (Phd). He said the only way a compressed mag spring will lose its resiliency is if it experiences 'creep' which requires high temperatures IIRC (it's been a while). One thing I found interesting is that steel has an endurance limit, meaning if you compress a spring within its elastic region below a certain load then it can withstand an infinite amount of stress cycles. Above this load the cycles to failure become finite.

Aluminum, for example, does not have an endurance limit and even under a light load will fail after some amount of cycles.

Cliffs notes: load 'em full

May 7, 2004, 03:48 AM
Ukraine Train summed it up nicely.

The problem is that in todays bean counter society things are not designed with any "headroom". Too many mechanical devices today are designed to operate at the max and therefore will fail faster. Cheap metal and cheap springs do not a quality magazine make.

Have you ever known anyone who wore out a magazine spring on a 94 Winchester? Or an '03 Springfield? M1 Garand? Unmodified S&W Hand Ejector? How about a '57 Chevy Bel-Aire? Unless it's been overloaded or abused the springs should still be good. In fact the ones that have been activally driven are in better shape.

A properly designed spring will last forever when used appropriately.

May 7, 2004, 11:12 PM
Having been in the business of making springs (die springs, valve springs, etc.), I can tell you guys that if the spring is designed correctly, manufactured from the correct material, and stress-relieved properly it will NOT fail.

Not from lengthy compression, nor from cycling.

I would assume that springs used by any reputable manufacturer will meet the design tolerances adequately. BTW, our die springs were designed to exceed six million (that's 6,000,000) cycles. Typical failures would be from breakage, not from "taking a set" (which is the trades' phrase for losing free length).

Poorly manufactured springs typically will "take a set" when repeatedly cycled to full compresson, i.e. coils bottoming out on each other. A good springmaker will compress the spring to "solid" midway through the process to eliminate this as a factor later.

This is a simplifiction of the process, but the story about magazine springs will "take a set" or lose resiliency probably came about from the use of really inferior springs.

May 8, 2004, 04:37 AM
Moondancer- you've absolutely got it!

Except I would estimate there are a large portion of vendors in teh firearms community who gave absolutely no thought to proper spring selection (in terms of longevity.)

I think there are a lot of crap mags out there.

The good ones, however, will last a lifetime (or three) quite literally, as you said.

PS: The whole 'download the M-16" thing came from soldiers who couldn't count, and actuallly were loading *21* or *22* rounds into their 20 round mags.

Of course, they expierenced jams (and likely died, sadly.)

Thus, the word-on-the-street became to down-load to avoid jams. It wasn't a weapon fix, it was an operator one.

Chris Rhines
May 8, 2004, 08:27 PM
I load my AR magazines with 18 rounds instead of twenty. It is much easier to seat the magazine on a closed action when the magazine is downloaded.

I've never had any function problems when loading the mags to full capacity, but downloading them makes them easier to handle.

- Chris

May 8, 2004, 09:47 PM
This question always gets a lot of theoretical and "ideal conditions" answers.

Real world.

Some doublestack mag designs heavily compress the spring when fully loaded and will experience spring failure much more rapidly when fully loaded than when underloaded by two.

I don't know that I've ever heard of this happening with single stack mags.

If you want to know if fully compressing a spring changes its characteristics, just post that it's hard to load the last round in your mag...

All the people who just posted that fullly compressing a spring doesn't affect it will advise you to fully load the mag and leave it loaded for awhile.

Now, if fully compressing a spring has no effect then why would fully loading the mag and leaving it for awhile make any difference at all?

May 8, 2004, 11:55 PM
Most gun springs are NOT made like industrial or automotive springs. They are simply wound from "music wire" and used as is. They are not chrome silicon steel or other appropriate alloy; they are not heat treated after winding and they are not stress relieved. Small wonder they have short and unpredictable service lives.

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