Are we SURE compression doesn't weaken mag springs?

[Candiru]

During today's trip to the range, a relatively new and clean Kahr P9 surprised me with a FTE. Specifically, the casing jammed lengthwise between the barrel and the breech face. I naturally suspected weak magazine springs, so I checked the magazines when I got back. Sure enough, one of the magazines' springs was about an eighth of an inch shorter than the other; a magazine assembled using that spring was noticably easier to load. My current working theory is that the FTE occurred due to a combination of limp-wristing and weakened spring. I think I was limp-wristing at the time because I also ended up getting smacked in the face by an ejecting round a bit later.

The first thing that occurred to me was that the spring was weakened due to compression, since the gun had been loaded for about three weeks; however, research shows the consensus to be that weakened magazine springs come not from long-term loading, but from frequent loading and unloading. Muddling the issue further is the fact that I can't remember whether the magazine in the gun at the time was the one that had been loaded, or the one that I used for several thousand snap-caps' worth of function testing.

What do you think? Was it all those snap caps cycled through the magazine that weakened its spring, or was being loaded for a long time to blame? Also, if there's another explanation for what could have caused the failure I'd love to hear it; I've never experienced a single failure in a Kahr before, so this has me slightly spooked.

 

[Lone_Gunman]

I think you need to ask a mechanical engineer about spring fatigue, not the loons that hang out on gun boards.

 

[cslinger]

All I know is I have shot magazines that have been loaded for years with no problems.

I have seen 1911 magazines that have been shot after being loaded for decades with no problem.

Now is it worth the few bucks to change springs every few years, absolutely. Do I think my guns will function after being loaded for some time....absolutely.........and if not that first round should keep their heads down long enough for me to run for a revolver.

 

[Owen]

I am a mechanical engineer. Fatigue is caused by cycling, not a single compression.

 

[Sam]

Are WE sure. WE, You talking French or you got a turd in your pocket?

I am sure, but I don't know about you and your french buddy


Sam

 

[Candiru]

owen: Thanks for the verification. Looks like I was shooting the mag I cycled to death.

Sam: Both my French buddy AND the turd in my pocket said keeping the mag loaded weakened the springs, but I figured neither of them knew what they were talking about. Looks like I was right. That's the last time I trust a Frenchman or a talking turd!

 

[chris in va]

All I know is a Wolff extra power mag spring I bought became over an inch shorter after the mag was left loaded for a couple weeks.

 

[mattw]

i read on the wolff website where they said to ignore the length changes of the spring and just worry about how it is functioning. it will change length as it gets broken in.

 

[mete]

If the magazine spring is PROPERLY MADE it will never see a fatigue failure or 'take a set'. I for one have never replaced a magazine spring on any one of my guns !!

 

[Zach S]

I think its a gray area.

The springs in my P14 magazines wore out pretty quick IMO. After replacing the springs within a year of buying the magazines, I started loading them one round down, and the replacement springs are still in there two+ years later, and they still work great (I am expecting issues any day now though).

I've also experianced short spring life with eight round 1911 magazines (although not as short as the P14 magazines). Now I only buy seven rounders, and dont have any problems.

 

[Double Naught Spy]

During today's trip to the range, a relatively new and clean Kahr P9 surprised me with a FTE. Specifically, the casing jammed lengthwise between the barrel and the breech face. I naturally suspected weak magazine springs, so I checked the magazines when I got back. Sure enough, one of the magazines' springs was about an eighth of an inch shorter than the other; a magazine assembled using that spring was noticably easier to load. My current working theory is that the FTE occurred due to a combination of limp-wristing and weakened spring.

I think you are assigning blame without any real idea of what happened. You had a failure to eject and blame the mag spring because it is 1/8" shorter than your other one. That doesn't sound too reasonable based on a singular incident. 1/8" isn't much. Plus, you noted you were limp wristing. This will happen with perfectly fine springs, if you limp wrist bad enough. Could it be a combo? Sure, but limp wristing sounds more plausible.

 

[walking arsenal]

My dad gave me a smith and wesson 39-2 9mm when i graduated highschool. As far as i can remember that gun had been loaded in his safe since i was born, so it had been loaded for at least 10 years if not more. i took it out and shot it once and a while and never had a problem with it. The mags are originals and have never had a mag spring changed. It's a family heir loom now and resides in a glass case.

 

[Onmilo]

Your first sentence explained it all,,,,, KAHR

 

[Walt Sherrill]

What I can find on the subject says that working the spring strains it, as does pushing it toward its limits -- compressed or extended. (This second point -- pressing toward design limits -- is a point the Wolff makes clearly on their website. That's why hi-cap mags are problems: the springs used are often the same springs as are used in lower-cap mags -- and they must be compressed more fully when the mag is fully loaded.

Wolff suggest that if storing a hi-cap for long periods, download it a round or two, so that the spring isn't pushed to its limit. For a standard cap mag, like a Colt 1911 7-rounder, its simply not an issue. (That's why 1911s stored for 50+ years will function properly when fired with the original mags.)

All that makes sense: working the spring will fatigue it; compressing a spring fully (all the way) will fatigue/stress it; stretching a spring will fatigue/stress it. A non-hicap mag used normally, will last almost forever; hi-caps will show signs of failure much more quickly, shooting the same number of rounds.

 

[Sam]

Candiru,
Don't take it personal, hard to resist the "we".
That's quite the nasty moniker you have assumed, anything behind that?


Modern doublestackers are almost by definition looking for trouble. With teh emphasis they pace on capacity they are going to go out of their way to reduce the margins of durability (and maybe safety) trying to stuff more in a smaller package. The 8rd 1911 mags are in teh same category. The thing was designed to hold 7 and will run till h@!! freezes over that way, jam in 1 more and trouble abounds. Most of the 7's would shoot with ben followers and even slightly boogered lips. Not the 8's. A BHP with original mags held 13, todays aftermarket types work hard to jam in up to 17 in some cases. 13's work and last, the bigger ones??????
The farther you get from the original well engineered design the more troubel you will have.

Sam

 

[mmike87]

Compressions does not weaken springs, cycling does. No, I am not a mechanical engineer, but I did stay at a Holiday Inn Express the other night.

 

[hifi]

To echo, compression does not cause spring fatigue, so long as the compression is within the original design specs.

 

[enfield]

If you're seeing variable results, it's not because spring design is a 'gray area'. It hasn't been gray in decades. What you're probably seeing is variation in the quality of the spring design, the quality of the spring manufacturing, the quality of the spring material, and the quality of your testing procedure.

Just because supplier X sells expensive magazines doesn't mean that they're designed or manufactured better than supplier Y's magazines. Price has nothing to do with quality: good engineering has everything to do with it.

BSME '71 and Certified Gun Board Loon

 

[1911Tuner]

Springy, Sprung, Sprang

hifi and Walt pretty well nailed it...but there's one other fly in the ointment.
The name of the fly is quality...or rather lack of same. If a spring is well-made, properly heat treated and tempered, and within design specs, full compression shouldn't change it beyond taking its initial set...which is allowed for during the engineering.

In today's manufacturing scene, the trend has been to outsource and count pennies. The lowest bidder gets the contract. Sometimes, the lowest bidder cuts corners to maintain the profit margin deemed acceptable by the ones counting the pennies...and things can go awry from there.

In my own experience, factory magazines that have been supplied with pistols
haven't been quite up to snuff for well over a decade now...regardless of the
gun maker. The noteable exception seems to be Metalform's stainless 1911
magazines, which usually...but not always...come standard with the Wolff spring upgrade. The blued ones don't, as evidenced by the otherwise good mags that come with the GI Springfields. The problems with those 7-round mags are neatly corrected by simply ordering the Wolff 11-pound springs from Brownells.

For the record, I have Wolff springs in all my mags....and I use my range mags a LOT...mostly Metalform, but a few factory Colt mags, some of which are also Metalform...and 30-odd original WW1 and WW2 contract GI magazines. (7-round only, thank you.) The springs have been in place for several years and untold tens of thousands of rounds, and they haven't failed. They have been left fully loaded for weeks at a time, and they work in all my guns...Commanders and GM-length alike...and have even been used to provide reliable feeding and slidelock to a few finicky Officer's Model/Defender class of pistols when the owners couldn't accept that their magazines were causing most of their problems. Yes. That includes the high-dollar trick mags from various insundry suppliers, which often don't deliver as promised.

Bottom line...If the springs are good, they won't fatigue from being left loaded for months or years. If they're not, they just might.

 

[Hypnogator]

Bottom line...If the springs are good, they won't fatigue from being left loaded for months or years. If they're not, they just might.

+1

 

[ShelbyV8]

My S&W 4516 Mags have been loaded for 12 or 13 years and still work fine. By the way my valve springs are 16 years old and have over 100,000 miles on them and still hit the rev limiter.

 

[JohnKSa]

It does, and it's easily demonstrated. Spring piston airgunners have known for years that leaving a spring fully compressed weakens it. In fact there are tests showing how the muzzle velocity drops in proportion to how long a spring-piston airgun is left cocked. (Most airgun designs compress the spring to coil-lock when cocked.) The better the quality of the spring, the lower the loss, but they all lose some velocity (spring strength) after they've been left with the spring compressed for long periods.

owen's comment is true, as far as it goes, but that is not the entire story.

Compression isn't a major factor in spring wear IF the spring is well made of high quality materials AND it is not compressed beyond a certain point.

Single column mags seem to be designed such that they don't get overcompressed and as a result they tolerate being fully loaded for long time periods very well. Some double column designs are not so easy on the springs and the springs in them will show noticeable weakening after being left fully compressed for a relatively short amount of time.

One of the best examples I have of this was a torture test I read in a magazine some years ago. They were testing a pistol with a double column magazine. Initially they loaded the two magazines to full capacity each time. After only about 2000-3000 rounds, both magazines began to cause malfunctions due to weakened springs. They replaced the magazines and continued the test but this time always underloaded the magazines by 2 rounds rather than fully loading them. The magazines finished the 10,000 round test with no further incidents. Clearly the second set of magazines tolerated many more cycles, but weren't compressed as deeply and therefore didn't weaken significantly.

 

[enfield]

Weakened springs after 2-3000 rounds is strong evidence of poor initial quality. Material, design, manufacturing, assembly, etc -- something was wrong.

When I was working at a auto company, we routinely tested springs for 10 million cycles -- and they passed.

 

[DelayedReaction]

Another mechanical engineer here, echoing that fatigue is caused by cyclic loading. Objects under constant stress are subject to creep, but that's only significant when the temperature of the material is above half the melting point. Unless you're storing your loaded mags at 1250 F, it's not a problem.

 

[enfield]

A few further thoughts:

Yes, springs fail. Compression set (plastic deformation) is a failure mode, not a cause of failure. Poor quality is the cause of compression set failures. Properly designed, high quality spring systems will give you more than a lifetime of service.

If a manufacturer can't reliably make high quality magazines, it's not an indication that the task is impossible. It is an indication that the manufacturer doesn't really know what he's doing.

Failure is not a bad thing -- it's a good thing. Failure helps you sort out the magazines/springs you can rely on from those you can't rely on. If you're relying on these magazines to help protect your life, one magazine failure (unless it can be attributed to damage or incorrect assembly) would be enough for any reasonable person to stop using, forever, that brand of magazine or spring.

For your defensive guns, find and stick with the magazines and springs that ALWAYS work for you. If you can't find any, maybe it's time to change guns.