Questions about Springs - recoil

[gsdelong]

I have two probably basic questions about recoil springs, I hope someone would answer for me.

1st Question is when a "17lb" recoil spring is designated what exactly does that mean? Does it mean it will not move at all until 17lbs or is 17lbs the minimum amount to compress it fully or something totally different.

2nd Question I am assuming the answer to question #1 is going to give me some insight here, what is the best way to tell multiple recoil spring weights apart?

Thank you

Greg

[AggieEE]

IIRC a 17lb spring will compress 1" with 17 lbs applied. It should be fairly linear needing another 17lb for the next inch etc. In answer to number question 2 is don't mix them up to begin with, smart a** answer, look at the diameter of the wire. thicker is stronger. Number of turns per inch figure in but I don't remember off the top of my head which way it goes. Somebody sells a spring checker, Brownell's?, that has a guide rod and weights that you can measure the spring rate. Hope this helps.

[gsdelong]

IIRC a 17lb spring will compress 1" with 17 lbs applied. It should be fairly linear needing another 17lb for the next inch etc. In answer to number question 2 is don't mix them up to begin with, smart a** answer, look at the diameter of the wire. thicker is stronger. Number of turns per inch figure in but I don't remember off the top of my head which way it goes. Somebody sells a spring checker, Brownell's?, that has a guide rod and weights that you can measure the spring rate. Hope this helps.

Thank you for the reply

[ulav8r]

More turns per inch makes a softer spring, if the wire size is the same.

[Harry Tobin]

This is what I have found to be true
Wire Thickness
16lb .044
17lb .045
18lb .046

Springs start out around 6 5/8 to 6 1/2 inch and get smaller and when then get below the 6 inch mark they are at the end. It is said that a recoil spring has a 2000 round life. I ended up wearing one out in 3 weeks and wanted a way to check the so I built a spring tester or you can buy them. Hope this helps you out, when I wore out my spring this is how it went. Started with 18 1/2 lb spring and not keeping track of how many rounds started to give me trouble and checked it and was down 15lbs 10oz. So now I keep track of how many rounds and test the spring when I get back form the range. Gonna do a video on that soon

https://www.youtube.com/watch?v=G1I7nf6y19U

[Ballistics in Scotland]

Imagine a long piece of wire sticking horizontally out of a wall. The weight required to produce a given deflection depends on the thickness of wire, and on its length. The longer the wire, the easier it is to bend.

Just as a screw is just a long inclined plane wound into a cylinder, like the old prints of the Tower of Babel, a coilspring is that wire wound into a helical shape. The more the coils and the wider the diameter, the longer the wire that is being deformed. So the more the coils and the wider the diameter, the less the weight required.

Then there is the issue of preload. In the example given, install it without preload, and it takes 17lb. to move the breechblock an inch. Install it so that it is already compressed an inch, and it takes 34lb. to move that breechblock an inch. Firing-pin and recoil springs for unlocked actions require some preload for safety, to prevent ruptured primers and premature opening respectively.

With specific firearms, and air-rifle mainsprings, it would make a lot of sense to specify the weight required to compress the spring from its at-rest position to the position in which it either cocks the action or ejects and reloads from the magazine. I don't know if this is ever done, though.

[gsdelong]

The issue here is that as usual what makes sense is probably not the common practice.

What I am trying to figure out is if a 17lb recoil spring is specified and I have a group of springs how do I know if the one I choose is 17lb

I suppose I need to stipulate let us assume we don't have an known 17lb spring to compare it to

In my day to day practical life I would just order a new 17lb spring and be done with it, but inquiring minds want to know

[williamwaco]

Let's turn it around.

If I don't have a jig or fixture to measure the compression with the 17 pound weight, could I suspend the spring from above and hang the weight and measure the stretch?

[gsdelong]

Interesting do you think the are corelated? Or is that your question?

Let's turn it around.

If I don't have a jig or fixture to measure the compression with the 17 pound weight, could I suspend the spring from above and hang the weight and measure the stretch?

[AggieEE]

Within reason should be linear. compression or tension. But then again, piece of 2x4, 1/4" dowel and a fender washer with a 1/4" hole and you have a compression spring tester.

[country gent]

The spring testers we made at work were a simpe affair. A c frame over a scales with a hole drilled thru it for the spring some were tubes to hold the spring straight or the rod was a slip fit in the coils above the spring some both. this had a flat head on it and a heavy weight 20-25lbs sat on it to compress it the scales read what the spring produced from the compression. The rod tube or frame cant touch or bear on the scales only the spring for accurate readings. You can get a good idea of spring force from wire dia if you have known ones also.

[fourarmed]

In the case of 1911 pistols, the pound rating of the recoil spring is the force needed to compress the spring to the length it is with the slide retracted all the way. It is NOT the spring constant in pounds per inch. Another way to think of it is: It's the force needed to hold the slide all the way open.

[Harry Tobin]

I'll do this as you asked by 1 and 2


1st Question is when a "17lb" recoil spring is designated what exactly does that mean? Does it mean it will not move at all until 17lbs or is 17lbs the minimum amount to compress it fully or something totally different.

A recoil spring is rated at full compression of gun, slide full back. So the slide back for a 17 lb spring you will get 17 lbs of force. With use of the gun the spring will weaken to the point of the gun not working correctly. For myself I run a 18 1/2 spring and after so many rounds have seen it go below 16 lbs. It makes the recoil harder throws the brass a long way and is hard on the gun. And the full compression length for a 5" full size 1911 is 1.625 inches, much more than that the coils will bind on the spring


2nd Question I am assuming the answer to question #1 is going to give me some insight here, what is the best way to tell multiple recoil spring weights apart?


This may be more difficult not knowing how much use the springs have had. If you have a set of Calipers you can measure the wire thickness to get in the ball park. Also if the spring had use it's poundage will be down. I'd say go with measuring the wire would be a good way to go, without a spring tester like the one I built it's a **** shoot. Also not all manufacturer use the same number of coils. What I would do if using different weight springs is clean the spring real good and paint the last inch of the spring a different color for each weight. For the diameter this is what I found on my springs
16 lbs .044
17 lbs .045
18lbs .046
Still not a absolute way of telling but should help.
Now there is one more part of this and this is what I call free compression that is the distance of the spring in the gun when slide is full forward. The distance in my 1911 is 3.783 and that will be a reduced poundage of the spring, for instance my brand new 18 1/2 spring at free compression gave me 10lbs 6ozs.

I'm keeping track of this spring and how many rounds go thru it and every time I come home and clean it I measure the spring rate. When I run the spring to it's end I'll do a video of it with all my data on it. Sometimes there is not a simple answer

[Geezer in NH]

Lets say I have a 15 pound spring it functions but the recoil is bad feeling steel on steel.

I get a 17# it functions and I do not feel sharp recoil.

I then get a 20 pound rated it only works with real hot loads that hurt anyway!

Who knows? I use factory rated springs from usually the maker of the gun.

Hot loading I will pass as no need IMHO

[wv109323]

Let me take a stab at this.
Mechanical Engineers and gunsmiths do not use a common language when talking about springs.
Gunsmiths or a least for the 5" 1911 use a poundage rating for a spring. This means a 17 lb. spring requires 17 pounds of force to compress the spring to the maximum compression when the slide is at full travel. The length of the spring at that point is close to 1 5/8".
Many factors enter into the poundage of a spring. Those being wire diameter, type of metal used, wrap or coils per inch or coils per specified length and free length of the spring. Proper spring design does not stress the metal beyond its elastic limit so theoretically it should not wear out. But with the minimal cost of springs it is quite common to change them at some interval.
Just as there are countless manufacturers of 1911's, there are just about the same amount of people making springs. So quality and design are all over the place.
There is usually 20-30% variance of the same poundage from the same manufacturer. There is 30 to 40% difference for one mfg. to another.
So without a way to measure poundage the best way to find a proper spring for your 1911 with your load is to shoot one round at a time. Increase spring poundage until the slide will not lock back on a consistent basis. Go with that spring or one one pound lighter.
Also spring poundage affects the velocity and momentum of the slide returning to battery. So a heavy spring increases wear on the bottom barrel lugs and slide stop pin when the slide slams home. The bottom barrel lugs push the barrel up in the slide and stops forward travel. Most people think of the damage of recoil but never think of the damage to the pistol when the slide returns home.
So the moral of the story is 16 pound springs are a good place to start. Don't reinvent the wheel, unless you shoot light loads or have optics mounted to the slide.
Now comes the witch doctors with flat wire springs and double springs and spring guides and so forth. There is no need for that in a 5" gun. Of course things change when you have a 4" or Commander length barrel. And caliber upsets the apple cart for required poundage. Round coils springs are still perfectly fine in the 4" application. But the world changes when you go to 3" barrels. You need the required poundage over a short distance with a much lighter slide. Flat wire may be the way to go there.
Mechanical Engineers usually refer to a spring by its rate. That is usually pounds per inch of compression. So a spring rate of 16 requires 16 pounds for the first inch ,32 for the second inch and so forth. You can also preload a spring and that preload must be met before the spring starts to compress. There are other parameters tha ME consider when designing springs but I just want to make the difference between poundage and spring rate.

[Ballistics in Scotland]

1st Question is when a "17lb" recoil spring is designated what exactly does that mean? Does it mean it will not move at all until 17lbs

The former of these, at least, can't be true. Unlike overcoming a constant force, such as lifting a weight, no force can be too slight to make a perhaps invisible deflection of the spring.

You can make a good comparison of two springs by applying a force to the two of them, arranged end to end, with a rod or tube to keep them in line. The deflection is for practical purposes linear, which is why spring balances have a linear scale, with the same size of graduations from top to bottom.

[gsdelong]

A lot of good information I appreciate it.

Although I would like to point out a 1911 was never mentioned on my part

I simply wanted to understand recoil springs more, the questions have come from problems with a lone wolf long slide in 45 acp with a red dot mounted on the slide.

Question #3 may be how that setup could take the same recoil spring as the standard length stock Glock slide and barrel which weighs considerably more

[Clark]

Here is 1911 commander on my mill so I can measure position and pulling on a Wagner force gauge so I can measure force [in earth pounds].
Notice the friction hysteresis.
Notice the cocking the hammer hysteresis.

I have a lot of springs in there, I have been shooting 45 Super level loads with Starline +P brass [thick walls above the web].