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Originally Posted by Kevin D77
You are correct, there are other ways to ruin springs. But a magazine that is designed properly should have excess compressive capacity built into the spring, a safety factor if you will, that should exceed normal compressive loading expectations.
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I added the underlining, above. That's a good point, and that's why most mag springs won't fail.
The problems arise when they try to stuff 17 rounds into the same space they once stuffed 10 or 15, or when the gun makers try to 8 rounds into a compact mag that probably would do better with 6. Then "normal compressive loading expectations" go out the window.
Over the past couple of years, gun designers have been making smaller guns do more, and bigger guns do more too. In doing that, they've pushed smaller barrels into smaller frames, and asked those guns to handle the same recoil. They've also made small gun have almost the same capacity as full-size guns. Springs are what gives. They have become, for those guns, at least, a renewable resource.
If you compare recommended cycle lives (shot counts) on recoil springs for the sub-compacts, they're much shorter than the guide lines for full-size guns. If it was primarily "cycling" the springs that led to a shorter life, that should NOT be necessary (i.e., shorter life for recoil springs in compact guns). But since smaller springs are being asked to do as much work as larger ones, something has to give. Spring life, it appears.
Your point is that a properly designed spring properly used should live a long life. Good point.... and why we keep hearing about WWII 1911s, found fully loaded, but stored for 40-50 years, working like new. There was reserve built into those 7-round springs.
I have been a CZ enthusiast for years. The standard 75B first came with a 15 round mag, and they later (during the ban) sold a bunch with 10-rounders. CZ Mags now can be had in 10, 15 and with a different base and follower, 16, 17 18+ round capacities. They all seem to use the same spring.
The 10-rounders will arguably last forever -- I've never had to replace one. Most the the 15 rounders will do pretty well, but the rest of them may not live as long,
because the same spring is doing more work for the same number of rounds fired. Fully loaded, that 17-round mag is holding and trying to lift 7 more rounds than a 10-round mags -- {B]it's working even when it's not moving[/B]. If that work occurs when the spring at it's elastic limit (what you might call normal compressive loading expectations), all bets are off.
The engineer that posted the links in my response -- you can probably find the whole chain of messages if you patiently search -- noted that degradation occurs NOT just at high temperatures. And members here who know about air guns affirm that leaving a spring-powered air gun cocked is a sure way to kill the springs. There's a lot of folks who shoot air guns. Talk with them if you can. Some gun springs are now intended/designed to be disposable and NOT last the life of the gun.
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