Magazine spring questions

**Ds J** · 31-03-2023, 01:16

Some questions on magazine springs which have been circling my mind of late:

How are magazine springs designed ie what does an engineer consider when designing a magazine spring?

What are the criteria, and what are the tolerances?

Also: what materials are generally used, and why?

**Marius@Jizni** · 31-03-2023, 11:50

Trial and error.

The first trial being: "What else do we have that will fit?"

People have this romanticised view of how perfectly the OEM engineers design these things. Remember that the spring starts out stiff, but gets weaker with every cycle. So there is no sweet spot to start off with - just a range.

So what I'm seeing is new guns being released using the same springs as older guns, or different length magazines using the same spring. Then after a while, you pick up that the factory has changed one of the springs, so now they use different springs. Or the other way round. Some pistols may have their own, specific parts, and then you hear that they now use the same part as some other gun to save on inventory costs.

**Ds J** · 31-03-2023, 13:54

Originally Posted by Marius@Jizni

Trial and error.

The first trial being: "What else do we have that will fit?"

People have this romanticised view of how perfectly the OEM engineers design these things. Remember that the spring starts out stiff, but gets weaker with every cycle. So there is no sweet spot to start off with - just a range.

So what I'm seeing is new guns being released using the same springs as older guns, or different length magazines using the same spring. Then after a while, you pick up that the factory has changed one of the springs, so now they use different springs. Or the other way round. Some pistols may have their own, specific parts, and then you hear that they now use the same part as some other gun to save on inventory costs.

Technically, I could try a Beretta spring in a CZ magazine and it might just work?

**M43** · 31-03-2023, 17:02

Originally Posted by Ds J

Technically, I could try a Beretta spring in a CZ magazine and it might just work?

I have fixed a Star M30 mag that didnt work by replacing the spring with a Z88 spring.

You may have to fidget a little with the bottom coil to get it to work with the CZ's retainer plate but it should work.

**M43** · 31-03-2023, 17:06

And on the subject of spring interchageability...

That same Star M30 with the fully functional mag using the wrong spring is about to get its recoil spring replaced with a CZ 75 spring. I just have to cut the CZ spring until it has the exact same compressed lenth as the original and then hopefully we're in business again... The actual wire is a little thicker and I suspect stiffer on the CZ but it fits over the recoil rod. So lets hold thumbs.

**Ds J** · 31-03-2023, 18:17

I was wondering whether the springs get design for a certain amount of upward pressure, simply because worn springs cause FTF's in my CZ 75.

**oafpatroll** · 31-03-2023, 18:44

Originally Posted by Ds J

I was wondering whether the springs get design for a certain amount of upward pressure, simply because worn springs cause FTF's in my CZ 75.

They will be designed as such. Theres a range within which they will work and from my observation it seems to be quite wide. Once they fall below whatever that minimum is my ridiculously reliable old 75 starts experiencing FTFs. I've got reasonably good at being able to tell when that point is being approached based on the under thumb feel when reloading. My mags are numbered and I rotate them to spread cycles. Must remember to maintain a record of ho many cycles the next one I replace lasts.

**A-R** · 31-03-2023, 21:23

I know what responses I will get already, but here are my 2c worth of experience on 9mm pistol mag springs:

I remove a new mag spring from the mag and measure it's length. This length gets recorded somewhere, like on the back of the pistol's user manual or similar.

As the spring gets weaker from use or abuse, it gets shorter. So when you compare it to the original length, you know how far it has gone. At some point it is too weak and causes a malfunction. Measure and record again, this is the point where the spring is now shot and needs to be replaced. So far so good.

Here comes the shocker: When a spring reaches that point, I simply stretch it out to the correct length again, and it works just like the new one. Yes, if you do this often enough, it will eventually break from metal fatigue. No big loss to me, as it was due for replacement way back when I stretched it out the first time anyway. Theoretically at least, as I have not managed to actually break one by doing so yet.

Mag springs can often be changed between makes of pistols. Most 15-round 9mm mags have very similar springs. Compare the length, and if you have a vernier, the wire thickness. This will give you an indication of it's suitability. Followers are shaped differently, and some modern followers are much smaller than the old type that had a tab sticking inside the spring and likely bottoming out against the base plate. Make sure the new spring fits the follower and angles it correctly.

**Vaal** · 31-03-2023, 21:59

A lot of shotgun guys failed the magtube spring exercise by cutting the brand new spring just the right length, but low and behold the spring shortens quite a bit as it settles. I normally install a new, too long spring, run it for a while and then only cut it shorter. Then it sort of stay the same length for quite some time.

**ady** · 01-04-2023, 09:22

All springs are not equal.

At one point, i couldn't find a spring for my semi-auto shotgun magazine tube, so i had a spring manufactured locally in PE. It was the correct length (1m), but it lasted 3 full mag tubes and it was 20cm shorter. The spring eventually became unusable.