From: "Julius Chang" <p00302@psilink.com>
Subject: Re: Keep Mags full???
Organization: PSI Public Usenet Link

#DATE:   14 Mar 1994 13:42:37 -0500
#FROM:   Gary Coffman <gary@ke4zv.atl.ga.us>
#
#In article <francis4-110394100525@dfrancis.apple.com> francis4@applelink.apple.com (Dexter Wm. Francis) writes:
##
##Is there any problem with feed spring fatigue in fully loaded
##magazines?
#
#If the spring designer, and the metallurgist, are competent, there
#should be no fatigue in a spring that isn't stressed beyond it's
#elastic modulus. Bad designs, or bad spring metallurgy, can allow

	"Stressed beyond it's [sic] elastic modulus" is technically
	incorrect.

	Elastic modulus E is the slope of the stress-strain curve.
	It provides an indication of the stiffness of the material.
	I assume that you mean to say "stressed beyond its static
	yield strength."

	However, fatigue can definitely occur due to cyclic loading
	below the static yield strength of the material.  Even absent
	surface stress risers (e.g., notches), fatigue crack nucleation
	can occur at grain boundaries, second-phase particles, twin
	boundaries, and other microstructural features which exist
	normally.

#spring fatigue. As a data point, I inherited a 1911 that had been
#loaded since WWI. The springs were fine, so was the ammo BTW. OTOH
#I have some off brand mags that suffered noticable spring fatigue
#after only being loaded a few weeks. You pays your money, you takes

	Since fatigue is a failure mode due to CYCLIC loading,
	your observation does not indicate fatigue failure.  A
	loaded magazine is a static situation, not a cyclically
	loaded one.

	It sounds like the spring was improperly designed and
	it suffered permanent deformation when the mag was loaded
	to the max and the spring got compressed beyond its limit.

	Fatigue is not a bending type failure.  It consists of
	crack nucleation/initiation, progressive cyclic crack growth,
	and catastrophic failure.  Fractographic examination of
	of the material commonly shows "river markings", i.e.
	ridges or striations which delineate the cyclic crack
	propagation.

#your chances. Frankly, I wouldn't use a magazine in a carry gun that
#I didn't have every confidence that it could stay loaded indefinitely
#with no harm.
#
#Note, springs that must flex rapidly, like your recoil spring, can
#fatigue with use. The reason is that the rapid and repeated flexing
#can raise the spring temperature enough in localized stress risers

	I've never heard of this as a fatigue mechanism.  Do you
	have a reference for this?

	My understanding is that fatigue failure is due to localized
	plastic deformation and dislocation (slip band) propagation
	and is not due to localized heating.

#to destroy the temper of the spring in that area. The load will then
#exceed the (reduced) elastic modulus at that point in the spring and

	As mentioned above, the use of the term "elastic modulus"
	here is incorrect.  A load doesn't exceed the elastic modulus
	since E is the slope of the stress-strain curve and measures
	stiffness.  What you probably mean to say is that "the load
	will then exceed the (reduced) yield strength...."

#allow it to collapse or even break. But a static load within the
#spring's design limits, like that in a stored loaded magazine, should
#never have this problem.

	By definition, a static load (e.g., a once-loaded mag
	stored indefinitely) can never produce fatigue
	failure.  You need a cyclic load (e.g., a repeatedly
	loaded and unloaded mag).

	-Julius

From: "Julius Chang" <p00302@psilink.com>
Subject: Re: Storage of ammo in clips?
Organization: PSI Public Usenet Link

#DATE:   22 Apr 1994 00:12:59 -0400
#FROM:   putzolu david <dputzolu@uxa.cso.uiuc.edu>
#

	[stuff deleted]

#As to spring weakening, there are two schools of thought on the
#matter:
#
#The engineers (ok, engineering students :) told me that if a spring
#is kept under constant tension and is within its deformation

	Shouldn't that be compression, not tension?

#limits, it should not get worse over time.
#
#Everyone else says that you should not keep magazines fully
#loaded, and at least half the people I know download by one or more in
#the high capacity magazines they have.

	But is this because of permanent spring deformation or
	just bad mechanical engineering design?

	If the spring permanently deforms when you load a mag
	fully, then I submit that such a spring is defective
	and should never have been sold.

	-Julius

	[rest deleted]

From: "Julius Chang" <p00302@psilink.com>
Subject: Re: Metal fatigue of magazine springs
Organization: PSI Public Usenet Link

#DATE:   26 Sep 1994 02:23:47 -0400
#FROM:   Staywet <staywet@aol.com>
#
#In article <3630ke$t11@usenet.rpi.edu>, schwae@rpi.edu (Eric A. Schwartz)
#writes:
#
#<<<<<<<<<In article <3627md$7ed@xring.cs.umd.edu>,
#Merrill Gibson <merrill@netcom.com> wrote:
##Can a magazine (like my Glock 19's) be left fully or partially loaded for
#
##extended periods (years?) without worry about fatiguing the spring?
##
#It will not fatigue.  Fatigue is a function of cyclic loading; if
#you leave the magazine loaded, it will not fatigue.  However, any
#polymer components in the magazine will deform over time, and stress
#concentrations in the spring will make it more susceptible to
#corrosion and weakening.  The bullets may also corrode somewhat
#inside the magazine, and will need to be replaced periodically;
#unloading and reloading the magazine can cause fatigue.  You can
#leave it loaded, but put a rust-preventative dry lubricant on the
#spring and walls first, and examine it periodically to make sure the
#bullets aren't corroding too.  Keep it in a place with little or no
#humidity.
#
#E.S.>>>>>>>>>>>>>
#
#well yeah thats sort of right, but depending what the spring is made of it
#will have some memory effect (if its kept loaded) , and creep effects
#metals too not just polymers.

	We are talking about regular steel alloys, not shape
	memory alloys.  There is no "memory effect."  And
	creep just doesn't occur at room temperature.  As a
	rule of thumb, creep processes occur at about 0.5Tm
	where Tm = melting temp.  I doubt that you'd survive
	for very long under those conditions, much less shoot
	very accurately.

	-Julius

From: "Julius Chang" <p00302@psilink.com>
Subject: Re: Metal fatigue of magazine springs
Organization: PSI Public Usenet Link

#DATE:   27 Sep 1994 15:37:26 -0400
#FROM:   Staywet <staywet@aol.com>
#
#In article <2989639758.2.p00302@psilink.com>, "Julius Chang"
#<p00302@psilink.com> writes:
#
#<<<<<<
#	We are talking about regular steel alloys, not shape
#	memory alloys.  There is no "memory effect."
##>>>>>>>
#Your terminology here is correct, and i wasent thinking of the nickel
#"memory alloys" when i said that.  I was just trying to keep it simple, ie
#the spring will tend to remember that it was compressed (a function of
#strain hardening, and plastic deformation).  If we really had a spring

	But a properly designed spring shouldn't plastically
	deform in the first place.  So there is nothing to
	"remember" anyway.

#with memory, we could just heat it and it would restore it self,- gosh
#what wonder full things came out of the space program :-)
#
#<<<<< And
#	creep just doesn't occur at room temperature.  As a
#	rule of thumb, creep processes occur at about 0.5Tm
#	where Tm = melting temp.  I doubt that you'd survive
#	for very long under those conditions, much less shoot
#	very accurately.
#
#	-Julius
##>>>>>>>
#
#Well that sort of depends on what phase your material is in, super cooled
#liquids like glass, some polymers, etc. Will creep just fine at room
#temperature.

	We are talking about steel springs used in pistol mags, not
	supercooled liquids and polymers.  I'm not considering
	viscoelasticity, anelasticity, or viscous flow here.

#Aluminum will also creep at room temperature, that effect has been noted

	No, it fails for two reasons:  1) heating and cooling cycling
	loosens the wiring at its connections (typically outlets and
	junctions) and 2) local heating due to the Al oxide layer
	producing high resistance (which exacerbates problem #1).
	It does not creep at room temperature.  Otherwise, I'd imagine
	that Cannondale bicycles and various bicycle wheels would all
	start sinking to the ground.  Al wiring fails because of
	thermal expansion/contraction combined with oxidation.

	The Metals Handbook Desk Edition, Chapter 32, says that
	creep deformation dominates in Al alloys above 400 F
	and 700 F for low-alloy steels.  Hardly room temp.

#as the cause of several fires, in mobile homes, and older buildings where
#aluminum wiring  has been used.
#
#In general creep will occur as a temperature effect, usually elevated,
#however some materials have been shown to deform plastically when placed
#under constant loads for extended periods, even when such loading was in
#the elastic region - hooks law.

	We are talking about steel springs under normal gun handling
	action.  Or at least I was.  Creep mechanisms like grain
	boundary sliding, vacancy diffusion, thermal softening, and
	dislocation climb all require thermal activation.  I stand
	by my rule of thumb for metals that viscous-like processes
	become important at temperatures above 0.5 Tm.  You'll
	also find this rule in virtually any metallurgy text.  Ok, some
	might claim 1/3 Tm, but hey, it's only a rule of thumb.

	BTW, it is Hooke's law.

	-Julius

From: jchang@whidbey.net (Julius Chang)
Subject: Re: Advice wanted: keeping magazines loaded
Organization: The Whidbey Connection

In article <3fd5md$9bc@news.CCIT.Arizona.EDU>,
keane@bigdog.engr.arizona.edu (James Keane) says:

	[stuff deleted]

#It is also important to note that the tests used to determine the
#elastic limits of metals is usually done for a brief duration.  Metals
#that are stressed for long periods of time can succumb to "creep" that

	Which alloys and at what temperatures?  I find it hard
	to believe that steels normally used in gun manufacture
	suffer from creep at room temperature.

#is not obvious from these short tests.  A number of structural collapses
#have been attributed to this,  even though the rebar used should have

	Please name them.  Exclude failures due to fire (high temp).

	-Julius

From: jchang@whidbey.net (Julius Chang)
Subject: Re: Advice wanted: keeping magazines loaded
Organization: The Whidbey Connection

In article <3fmg75$qc7@xring.cs.umd.edu>, bd474@cleveland.Freenet.Edu
says...

|In a previous article, jchang@whidbey.net (Julius Chang) says:
|
|#In article <3fd5md$9bc@news.CCIT.Arizona.EDU>,
keane@bigdog.engr.arizona.edu (James Keane) says:
|##
|#       [stuff deleted]
|#
|##It is also important to note that the tests used to determine the
|##elastic limits of metals is usually done for a brief duration.  Metals
|##that are stressed for long periods of time can succumb to "creep" that
|#
|#       Which alloys and at what temperatures?  I find it hard
|#       to believe that steels normally used in gun manufacture
|#       suffer from creep at room temperature.
|
|For what it's worth, permit me to add another data point. My father has
|as 1941 Beretta 9mm kurtz that he has kept loaded in a bedside drawer
|since he returned from WWII--never fired for almost 50 years.  The
|magazine holds something like 6 rounds; at any rate he only had it loaded
|with five.  Last time I was home I transfered the old cartridges to the
|spare (empty) magazine that came with the gun and is stored in the
|holster.  I noticed while manually "thumbing" the cartridges out of the
|old magazine that the last round wasn't being pushed up snug with the
|feed lips; I reloaded the old magazine and reinserted it into the pistol
|and manually racked the slide 5 times.  Sure enough, the last round
|wouldn't feed--it didn't stick up high enough to be raked off by the
|slide.


	This example says absolutely nothing about the failure
	mechanism.  Spring failure (normal plastic deformation
	or whatever failure mechanism you feel like picking)
	could have occurred when the mag was first loaded.
	Sitting in the drawer for another 50 years sounds incidental
	to me.

	-Julius

From: jchang@whidbey.net (Julius Chang)
Subject: Re: Advice wanted: keeping magazines loaded
Organization: The Whidbey Connection

In article <3gfi9d$1p3@news.CCIT.Arizona.EDU>,
keane@bigdog.engr.arizona.edu (James Keane) says:

	[stuff deleted]
#
#:       This example says absolutely nothing about the failure
#:       mechanism.  Spring failure (normal plastic deformation
#:       or whatever failure mechanism you feel like picking)
#:       could have occurred when the mag was first loaded.
#:       Sitting in the drawer for another 50 years sounds incidental
#:       to me.
#
#Justify it any way you like;  it sounds like you have already made up
#your mind,  and the evidence be damned.  That's fine with me;  just
#don't blame me if you hear "click" instead of "bang."

	Justify it any way you like; it sounds like you have already made up
	your mind, and the *lack* of evidence be damned.  That's
	fine with me; just don't blame me if you hear "click"
	instead of "bang" when you need that last extra shot.

	Explain to me how the story of the 50 yr. old. gun in the drawer
	story supports the claim that creep caused the mag failure.   Do
	you know what creep is?

	If you can present *sound scientific evidence* that room-temp creep
	causes mag springs to produce gun failures, I am perfectly
	willing to listen.  Ad hoc, anecdotal stories don't cut it with
	me.  Story-telling and then begging off from presenting
	evidence when asked to do so doesn't cut it with me.

	I don't doubt that fully compressed mag springs can cause
	problems.  But probably due to poorly heat-treated steel, grit,
	spring binding in the mag body, deformed mag body, etc.  But
	I believe that the original thread did not concern these failure
	sources; just creep.

	My personal experience is that my S&W and SIG
	mags have NEVER failed.  I keep them fully loaded all
	the time.

	-Julius

From: jchang@whidbey.net (Julius Chang)
Subject: Re: What happens to Steel?
Organization: The Whidbey Connection

In article <3hp9tj$nql@xring.cs.umd.edu>, leebrown@delphi.com says...

#To illustrate:  Take an ordinary wire coat hanger.  Place it on a table with
#one of the "shoulder" ends extending a few inches off the table.  Place a book
#over the portion on the table and hold it down firmly with one hand.
#
#Now, push the free end (the part hanging over the edge) down slightly,
#then let it go.  The coat hanger deflects slightly, but returns to its
#original position when released.  Now push on it harder, hard enough to
#bend it.  The coat hanger is now permanently deformed, and will not return
#to its original shape.  Is the coat hanger now now weaker than it was before?
#You bet it is!  that's why you can break a coat hanger by repeatedly bending
#it back and forth.

	I'm not sure what criterion you use to conclude that the plastically
	deformed coat hanger is weaker than the undeformed version.

	For steels, the material strain hardens and the stress-strain curve
	shows an ultimate tensile strength value that is larger than the
	initial yield point.  In my book, this means that the material is
	stronger.  Of course, it is also more brittle.

	-Julius