Will springs compress?

[Rastoff]

I am posting this here because a lot of people ask questions about M&P magazine and recoil springs. This was started on another site, but I'm including it here because it should interest many. I left the narrative alone even though the first part was written about a year ago.


Yes, I'm a geek.

Springs are commonly (and sometimes hotly) debated and discussed. "Is it OK to leave the striker cocked?" "Is it OK to leave magazines loaded?" are questions that get asked many times a year. There are those that respond, "You should always release the striker to increase spring life." Then there's, "Springs only lose power through use. A spring can be left compressed for years and it will still be just as good as new because it wasn't used."

Well, I'm putting it to the test. I got two springs:

These are 19lb Main Springs for a 1911. They represent the springs we see in many guns from shotguns to revolvers. As you can see they are the same length today.

Then, I compressed one:

I will leave it like this for a year. I know it will be left alone and untouched because I'm leaving for Afghanistan next Monday. I won't be back for a year.

After the year is up, I will put them side by side and see if there is any change. I hope I don't forget that I'm doing the test.

As with all things about guns, this will not settle the question. It will be an interesting test though.

---------------------------------------------------------------

OK, here we are 1 year and 10 days later. I broke my leg in training and never made it over to Afghanistan, but that is another story. The thing at issue here is the spring. It has sat for all this time and was not touched by me or anyone else until today.

Here is where it sat:

Here are both springs just before taking it out of the clamp:

Here they are side by side after removal from clamp:

The original question:

• Will a spring compress (lose power) by simply sitting in a static compressed state?

My hypothesis was:

• The spring will compress by remaining compressed over a long time. However, the amount of loss will not be significant to a firearm.

The result:
Yes, a spring will compress or lose power if left in a compressed state for an extended period. The spring under test did indeed lose length over the test period. After being removed from the clamp, it was shorter than the control spring by about 1mm. It is still my contention that amount of loss is insignificant to the operation of a gun.

Like most things with guns, I'm sure there will be many who will find fault with this test. Even so, it cannot be denied that the spring is indeed shorter. This happened simply from compression in a static state and not through many cycles of use.

 

[PastureOfMuppets]

I bow to your commitment and level of geekness.

Now you need to do it with a selection of differently forged material and made springs

 

[Tinn-Can]

Here I was thinking I would have to wait a year to find out the answer... The whole "springs don't weaken under compression" thing never made sense to me...

 

[leejack]

Now, let them sit side by side for a year and see if the compressed spring grows 1mm. LOL! Just kidding.

I applaud your test sir!

Bottom line to me is; load them, shoot them, rock & roll. They will last a long time loaded or unloaded.

 

[rdtompki]

Is the amount of compression representative of a normal cycle? It appears that the spring is almost bottomed out. I'm not a mechanical engineer, but I'm under the impression that a high quality spring in a partially compressed state (striker springs, I believe) will return to it's original length.

 

[SpringGunTunes]

Compressing a new spring is called "setting". Reduction in length is normal in any spiral compression spring. Once you set a spring it stays set. This does not fatigue a spring.
What should be measured is the spring "rate". As a spring is compressed the force required to compress it further increases. This is tested with a force gauge.
The continuois flexing of the metal is what reduces its rate.
This is a known fact of metalurgy and can be found with the click of a mouse. But don't search gun forums because only a few in there understand this fact.
Loading a spring does not wear it out or reduce the spring rate.
Leave your mags loaded and your strikers cocked.

 

[Kovariles]

Is the amount of compression representative of a normal cycle? It appears that the spring is almost bottomed out. I'm not a mechanical engineer, but I'm under the impression that a high quality spring in a partially compressed state (striker springs, I believe) will return to it's original length.

You are quite correct, a high quality, well designed spring such as a S&W product should never take up a permanent set (shorten) as a result of long term compression. Time spent in compression is not the critical factor. On the other hand, a high number of work cycles will affect the tensile properties, it is called fatigue. However, again, a well designed spring will have a very high level of fatigue life, probably in the order of several million cycles. Your gun and the springs in it will probably out last you. By the way, I don't work for S&W, I am just a customer like you guys.

 

[Rastoff]

See? I told you the debate would continue. Even with the proof right there in front of them, people continue to claim it can't happen.

Is the amount of compression representative of a normal cycle?

It might be. I can't see the inside of the mainspring housing with the spring installed. I know the hammer spring on my Ljutic is fully compressed when the hammer is cocked.

I suspect, but have run out of patience to test, that if the spring in the test were compressed less, the difference would be reduced proportionally to the amount less compressed.

As I have always said, a spring will compress (or set if you prefer that terminology) if left compressed for a long time. I have measured this effect in click type torque wrenches and now with this test. The amount of this compression is not significant to a gun, but is significant to a torque wrench. In other words, don't worry about your gun, but always remember to leave your torque wrenches a the lowest setting.

 

[PastureOfMuppets]

See? I told you the debate would continue. Even with the proof right there in front of them, people continue to claim it can't happen.

Your going to need to test the spring rate of both... but they should have been done beforehand.

Your going to have to do the whole thing over...