How are most mag springs wound? In a vertical spiral. That design means that the spring tension increases with each inch of compression. If the spring is compressed to nearly coil bind to get the maximum number of rounds into the magazine, does it now meet the specification preload pressure the gun requires?
Going back to the M16, it was originally designed for a twenty round mag, and then 30 rounders were fielded to add capacity. Does the stack pressure of a thirty round mag exceed the design load to strip off the first cartridge in the stack?
Nobody is saying what the actual spec figure is, even after 45 years of use. A lot of us find fully loaded large capacity magazines with spirally wound springs have a high stack pressure on the top bullet seated against the feed lips. Metal to metal, there is a high amount of friction. Metal to polymer, it's quite a bit less. Ergo, Pmags are more reliable, even tho they still use the spiral spring.
It's not the engineers who specify the spiral spring, it's accounting. It's cheap. The alternative is a clock wound spring, which unwinds as the magazine is loaded, and which retains a constant rate of preload. Pistol magazines have been designed to use them. The amount of preload is calculated by the need to push up a cartridge before the slide returns to battery.
Now things get complicated - because a gun can have such a high cyclic rate the bolt/slide returns to battery before the inertia of the stack of ammo moves the top one to presentation for chamber. Bolt override is the result, you get nothing in the chamber.
Under load the magazine, you reduce friction of the case under the feed lips, and the column inertia is reduced. So is the spring tension, but in a spiral wound spring, it's additive for every inch of compression and the result is that it's usually a lot higher than needed. What does it need? We're right back where we started, nobody is saying.
That's the difficulty of thinking that "properly designed mags won't fail." We don't know what a properly designed mag is, because we've been getting by with mags designed by the accounting department, and the engineers have to comply. Clock springs are expensive in comparison to spiral wound springs, and the public isn't very accepting of alternative designs in a hobby based on extreme conservatism. New designs aren't well accepted, we are still debating the reliability of the M16 45 years after adoption and fielding.
So, what is a properly designed magazine? We keep pointing to that goal, I don't think we know what it means. What we do know is that the top three things that cause malfunctions are magazines, ammo, and operator error. If we are getting properly designed mags, how then can they be the #1 source of problems across the board?
I conclude we aren't getting properly designed mags. What we are getting is what accounting and engineering compromise on.
Going back to the M16, it was originally designed for a twenty round mag, and then 30 rounders were fielded to add capacity. Does the stack pressure of a thirty round mag exceed the design load to strip off the first cartridge in the stack?
Nobody is saying what the actual spec figure is, even after 45 years of use. A lot of us find fully loaded large capacity magazines with spirally wound springs have a high stack pressure on the top bullet seated against the feed lips. Metal to metal, there is a high amount of friction. Metal to polymer, it's quite a bit less. Ergo, Pmags are more reliable, even tho they still use the spiral spring.
It's not the engineers who specify the spiral spring, it's accounting. It's cheap. The alternative is a clock wound spring, which unwinds as the magazine is loaded, and which retains a constant rate of preload. Pistol magazines have been designed to use them. The amount of preload is calculated by the need to push up a cartridge before the slide returns to battery.
Now things get complicated - because a gun can have such a high cyclic rate the bolt/slide returns to battery before the inertia of the stack of ammo moves the top one to presentation for chamber. Bolt override is the result, you get nothing in the chamber.
Under load the magazine, you reduce friction of the case under the feed lips, and the column inertia is reduced. So is the spring tension, but in a spiral wound spring, it's additive for every inch of compression and the result is that it's usually a lot higher than needed. What does it need? We're right back where we started, nobody is saying.
That's the difficulty of thinking that "properly designed mags won't fail." We don't know what a properly designed mag is, because we've been getting by with mags designed by the accounting department, and the engineers have to comply. Clock springs are expensive in comparison to spiral wound springs, and the public isn't very accepting of alternative designs in a hobby based on extreme conservatism. New designs aren't well accepted, we are still debating the reliability of the M16 45 years after adoption and fielding.
So, what is a properly designed magazine? We keep pointing to that goal, I don't think we know what it means. What we do know is that the top three things that cause malfunctions are magazines, ammo, and operator error. If we are getting properly designed mags, how then can they be the #1 source of problems across the board?
I conclude we aren't getting properly designed mags. What we are getting is what accounting and engineering compromise on.
