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Old September 12, 2011, 01:20 PM   #1
B. Lahey
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The Myth of Drum-Springs?

Around two years ago I got to questioning the widely held belief that the springs in common drum magazines will weaken over time if left loaded. That notion is undoubtedly incorrect regarding box mags, so I figured I would do a small-scale test of kalashnikov drums (75rd top-loading of eastern-euro manufacture, to be precise).

So I loaded up two of them and forgot about them until last weekend when I randomly rediscovered them while pawing through my ammo closet.

I took one to the range and it ran just fine. I think I'll let the other one sit for another year or more before testing.

So there you go. Probably not a big enough sample to be very meaningful, but still an interesting result against the conventional wisdom.
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Old September 12, 2011, 01:38 PM   #2
chris in va
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Old September 12, 2011, 01:56 PM   #3
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I'd not anticipate that leaving a drum loaded would weaken the spring any more than leaving a box magazine loaded.

With springs, barring any kind of metal fatigue, corrosion, or other problem, they wear out due to cycles, not to being compressed. If they do indeed fail due to prolonged compression, it's important to note that there is not one completely uncompressed spring involved anywhere on a given firearm. They're all compressed to some extent, be it a magazine, hammer, trigger, action, or whatever other spring.
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Old September 12, 2011, 09:57 PM   #4
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I received a PM asking that I clarify the amount of time the drum was left loaded.

It sat that way for roughly two years.
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Old October 21, 2012, 01:59 PM   #5
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3 Year Test Update

A few days ago I grabbed the other 75rd kalashnikov drum that had been sitting loaded for over 3 years now and took it to the range.

It also functioned just fine.
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Old October 22, 2012, 06:48 PM   #6
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Dang, I spend three years investigating a possible gun myth, and don't even get a "that's interesting" or a "good job, buddy"?

Tough crowd.
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Old October 22, 2012, 06:51 PM   #7
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Uh, thanks for clearing that up? I guess. Or something.
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Old October 23, 2012, 12:18 PM   #8
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Actually, good job. Any ideas for a follow up considering the "pressure against the feed lips" myth on AR STANAG magazines?

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Old October 23, 2012, 08:42 PM   #9
45_auto
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Quote:
I got to questioning the widely held belief that the springs in common drum magazines will weaken over time if left loaded.
Where did you hear that?

Can't remember where, but I've seen documentation of Thompson 45 drums and PPsH41 drums loaded during WW2 (around 70 years ago) that still ran fine when fired.

I think you need to go at least 100 years before your test means anything.

EDIT: This thread got me thinking, and I'm pretty sure I have some AK47 drums loaded up in the late 80's or early 90's. All I can say for sure is that they were loaded before the Clinton AWB. I'll try to remember to take a couple of them out next time I take an AK47 to the range.

Last edited by 45_auto; October 24, 2012 at 02:51 PM.
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Old October 23, 2012, 09:10 PM   #10
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Dang, very tough crowd

Thanks for the info (and anecdote about the Thompson drums), I feel less guilty letting my VZ58 drum remain full (it's just so convenient for transporting otherwise loose ammo). Good to know they're not as sensitive as pistol mag springs are supposed to be.

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Old October 23, 2012, 11:34 PM   #11
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I'm limited to ten rounds but good to know lol. And good job
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Old October 24, 2012, 11:00 AM   #12
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Hey Lahey load up for a 4 to six year test next!!
oh, and thanks for the testing.
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Old October 25, 2012, 08:55 AM   #13
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Lahey, if you don't mind, I would add another data point on the general issue of storage of loaded magazines.

I frequently come across loaded magazines (in firearms) in the property of the deceased. I don't ever recall a spring being fatigued to uselessness or feed lips looking bent.

However, I routinely see rust, dust and dirt result in a magazine that doesn't want to feed for unloading. Springs and feed lips may not be the weak point. Most of us have metal magazines, steel springs and environments that are to one degree or another dirty and humid. Those aren't the ingedients for long term reliability.
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Old October 26, 2012, 06:53 PM   #14
B. Lahey
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Quote:
Where did you hear that?
Every time there is a discussion of the benefits and drawbacks of the various kalashnikov drum designs, somebody states that the Chinese type is superior because it can be stored loaded, but not under spring tension. This is then stated to be preferable because the top-loadings designs will somehow wear out while sitting around loaded.

I know it sounds silly, but I have heard it many times. I'm somewhat amused that there are so many who have not heard it. Maybe drum myths have faded recently.
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Old October 27, 2012, 11:46 PM   #15
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However, I routinely see rust, dust and dirt result in a magazine that doesn't want to feed for unloading. Springs and feed lips may not be the weak point. Most of us have metal magazines, steel springs and environments that are to one degree or another dirty and humid. Those aren't the ingedients for long term reliability.
Beat me to it. spring steal will oxidize as easily as any other. That is obviously going to affect the spring strength, even after rust is removed. Binding, rusting together, and such can cause problems too.
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