Magazine spring myth

[tonzofphun]

If you bury them on the beach next to saltwater then naturally there will be some corrosion (or carry it on your persons with salty sweat daily) compared to storing them in a safe with a dehumidifier.

I think you meant to say this, right?

[bdickens]

Take a spring (any commercial compression type), measure it's length, at room temperature collapse it right up to it's Elastic Limit or Yield Point in a fixture and with it still compressed (near it's yield point at room temperature) cycle it through extremes of temperature (0F to 100F) 1000 times (a couple years worth) then decompress the spring and measure it again. Guess what happens.

This coming from another engineer. Me.

In all honesty, it boils down to the spring AND magazine design. If the magazine is designed where the spring compresses near it's elastic limit (fully loaded) and if the material chosen for the spring does not accommodate the yield point variance through the temperature range you will have deformation of the spring. Straight out of spring theory or strength of materials class 101.

Anyways, that's the straight physics of it. You can work the living caca out of a spring as long as it was designed properly into a system that keeps it well away from it's yield point throughout it's temperature range. If you don't trust me on this go outside and look up underneath your car/truck and tell me what you see. But compress a spring even once it up to it's yield point at a given temperature and then raise it's temperature thereby moving it's yield point and you will have a deformed spring. Some of our older makes of autos actually had this issue.

Now, do modern magazine designs take all this into account? I don't know or can speak for all of them. I do know that I have worn out AR mags that refuse to feed the last few rounds. As for my daily carry Glock mags I haven't seen any degradation over several years of daily use. But I will keep my eye on them.

I seriously doubt that the spring in a fully loaded magazine is compressed to its elastic limit. A high quality magazine, anyway.

[bravomikefoxtrot]

If you bury them on the beach next to saltwater then naturally there will be some corrosion (or carry it on your persons with salty sweat daily) compared to storing them in a safe with a dehumidifier.

I think you meant to say this, right?

Correct

[esxmarkc]

I seriously doubt that the spring in a fully loaded magazine is compressed to its elastic limit. A high quality magazine, anyway.

But technically you would be incorrect. As I stated earlier, the elastic limit changes as per the temperature. So if you wish to state "I seriously doubt that the spring in a fully loaded magazine is compressed to its elastic limit within temperature range of __ to __" then you may be correct on that. To know for sure I'd have to have the mag engineering specs that included the spring materials and hardening specs and my trusty old "Strength of Materials 101" book. It's those damn engineering details.

Myself, I can't say that with 100% certainty since I have 10+ year old Colt mags that are "compromised". The weak springs in them just wont feed the last few rounds up fast enough. And you can be sure those were built to MIL spec - (at least the manufacturer said so). But we know that engineers get things wrong (even myself) and manufacturers can cut corners.

Bottom line is know your hardware and test it occasionally. As someone here stated "Mags are cheap, life is priceless"

[ARS_Mechanica]

I agree with the OP, compression cycles have worn many mags over the years but left loaded or unloaded I have 30yr old mags that function like new.

[xb12s]

I seriously doubt that the spring in a fully loaded magazine is compressed to its elastic limit. A high quality magazine, anyway.

But technically you would be incorrect. As I stated earlier, the elastic limit changes as per the temperature. So if you wish to state "I seriously doubt that the spring in a fully loaded magazine is compressed to its elastic limit within temperature range of __ to __" then you may be correct on that. To know for sure I'd have to have the mag engineering specs that included the spring materials and hardening specs and my trusty old "Strength of Materials 101" book. It's those darn engineering details.

The temperature is NOT going to matter in real life with a quality spring. There is very little change in allowable stress or elastic limit between ambient and human extreme temperatures (120F). Now, there's no guarantee that Kimber (for example) wouldn't use some kind of crummy "pot metal" spring imported from China I suppose... I kid about Kimber because they give recommendations about some of their spring replacements after what is a ridiculously small number of rounds. Not the mag springs necessarily though. Good example of built in obsolescence.

[LAYGO]

My Dad wrote in his book about his time in Vietnam (late '65 thru '71 with the 1/101st), that they were encouraged to keep 19 rounds in their 20 round mags. Also, they would replace the bullet that was chambered overnight for fear of the humidity soaking in.

RIP Dad.

[ghostrider]

I think there were multiple sources.

I'm sure I read somewhere that the SAS (and other military units) were instructed to only load 12rnds in the Browning hi power 13rnd factory mags.

http://forums.1911forum.com/showthread.php?t=394851" onclick="window.open(this.href);return false;

[LAYGO]

I think there were multiple sources.

I'm sure I read somewhere that the SAS (and other military units) were instructed to only load 12rnds in the Browning hi power 13rnd factory mags.

http://forums.1911forum.com/showthread.php?t=394851" onclick="window.open(this.href);return false;

I also remember being told not to load over 18 rds of 5.56mm into the old 20 rd M16 mags. I gave up two rds, but made my Vietnam Vet platoon sergeant happy, who wanted us to avoid malfunctions. Maybe he was right; I don't know.

Actually you don't need to down load 20 round mags, that started from all the problems with early Vietnam era M16s- people were doing anything they could to make them reliable. 30 rounders do need to downloaded to 28- but not to make them more reliable, it's so that you can easily put in a mag with the bolt forward. When they designed the 30 rounders they didn't allow any extra space for the rounds to "give" under pressure of the bolt on top of them. Try loading a full 30 mag and a downloaded mag with the bolt forward, you'll see.

20 round mags = 20 rounds
30 round mags = 28 rounds

BHP mags I always load to capacity.

Makes sense. I know my Dad talked about the reliability of those early M16s.