The practical life span of magazine springs are based on cycles,
Springs are easy enough to change out though.
If you have ten or more magazines and rotate through them you’d have to burn up a lot of ammo to weaken all those springs,
Bullet setback in semi autos is a bigger concern.
Since all firearms at my indoor range have to be unloaded before entry, I simply eject the chambered round and add it to my training ammo cache for the launch.
First, I NEVER knew anybody that ever regularly unloaded a defense gun (this is never recommended). I do not know what good an unloaded gun is.
Although there can be issues regarding a round not chambering if a round exceeds maximum overall length if the projectile interferes with the lands and groves in the bore. That is not the danger of an improper crimp.
If a round chambers and goes into battery, you are generally good to go. The danger of an improper crimp is if a crimp is too tight, there can be excessive unsafe dangerous pressures built up prior to the projectile leaving the case from the cartridge after ignition.
As a retired LE Armorer a concern that I am personally aware of, occurred in a neighboring agency, when there was a dud with a good primer strike. It was determined by the ammunition manufacture that REPEATED rechambering of the round caused the primer compound to separate from the primer cup by the anvil area inside the primer cup. This made the firing pin strike ineffective. The ammunition manufacture recommendation as a result of this issue was NOT to REPEATEDLY unload and reload the chambered round.
It is a regular practice for many agencies for budgetary reasons to skip shooting up department carry ammo at qualification(S) (just using range ammo at the qualifications) and to place the old carry ammo back in service after qualifications. After 38 years of service, with the exception of the dud I described and the cause of that dud, I can factually state there are many agencies I have personally known to REGULARLY leave issued carry ammo in service for up to TWO YEARS without ever having any ill effects.
I suspect one problem with getting a clear answer on keeping a magazine spring compressed is that it depends on the design and materials of the spring itself. Some could be kept compressed for years without a problem, others might weaken after a few months of being compressed. Maybe an overgeneralization of cheap magazine, cheap spring would be in order.
If you start with a magazine that has a spring that won’t allow the last round to be placed in the magazine by hand (i.e., you have to use a magazine loader to get the last round in) then it probably can be compressed for quite a long time without weakening to the point of causing a malfunction. I’d extend that to magazines where you can get the last round in by hand, but just barely. You could also track magazines over time and when they go from near impossible to load last round to pretty easy then retire the magazine from the defensive rotation (or change the spring).
One trick IPSC shooters use, because they tend to have soooo many magazines, is to scratch a number onto them so we can keep track of performance and know which magazine might need maintenance or to be removed from circulation. Of course I recall keeping a separate set of magazines for practice and competition too. I don’t generally number my defensive magazines, but I’ve been thinking of starting to. That would make it much easier to track things like changes in compression as I could keep a spreadsheet with notes based on magazine number. Right now on the very very rare occasion I’ve had a feed problem with a defensive magazine I throw it in a box I have of bad magazines. That’s probably overkill (since it might not have been a magazine problem at all), but it has been so rare I haven’t tried to solve for it.
These are always interesting discussions. Many of us do different things, yet the same outcome is usually achieved unless your one of those people who never does maintenance, or go to the range. And if your one of those people, chances are your firearm will operate fine, but the user will be the variable in question.
For the sake of discussion, consider there are both revolvers and semi automatics, each with unique issues.
Semi auto ammo is taper crimped, both at the factory and by hand loaders.
This is a weaker crimp than a revolvers roll crimp, but allows head spacing on the cartridge mouth. Repeated chamber of a round can push the bullet back into the case, causing a dangerous pressure spike.
Revolvers are the opposite. Without a strong crimp, recoil from previous shots will cause a bullet to migrate forward, out of the case. Too far forward and the bullet will travel the gap into the forcing come and tie up the cylinder, which is why we use roll crimps on revolver ammo and taper crimps on semi auto ammo.
There are revolvers chambered for 9mm Parabellum as well as .45 ACP.
There are also semi autos chambered .38 Spl.
It isn’t usually a big deal, but it is something to be aware of
I wanted to report on “a test”. I had a pair of magazines for a Glock 22 that had been sitting fully loaded for a few years. Actually not fully loaded, I had them 1 round short to reduce the chance of weakening the spring. When I say years I mean at least 5 and probably 10. Not my usual style, but that’s what happened with these. The Glock 22 happily digest both magazines with no misfires or other malfunction.
Wow, thank you for sharing!
Ammo really does not have an expiration date. I have shot tons of ammo that was 20, 30+ years old and in probably 100s of thousands of rounds I’ve had exactly ONE factory round that failed to go bang and I know the reason for it, and it was my fault.
Regardless of this, when I get to the range the first string I shoot is with whatever “carry ammo” is in the gun. Then I practice with range ammo and after I clean the gun it gets reloaded with fresh carry ammo. Repeat as necessary!
I guess I’m in the minority here. I shoot a magazine of my carry ammo every time I go to range (weekly before COVID-19, not as often since), then replace it (I carry magazine in gun and spare magazine). I shoot off the one that was in gun, replace with spare, reload now spare with fresh. That way I also have a loaded CCW with full carry load when departing the range.
Why? I want to practice, at least a little bit, with what I might actually have to deploy. The $10 or less I spend doing that (probably closer to $6-$7) each range trip is more than worth it to me. And I absolutely know my CCW is functional.