Measuring spring weight

[Xringshooter]

I was given a bag full of mainsprings for Rugers (SA's and DA's). Is there an easy way to measure the weights without uninstalling the old, installing the new (over and over again) and using a trigger pull gauge?

[Mk42gunner]

You could make a fixture to hold the spring and use a gauge or weight to measure spring pressure. I would include a strut to support the coil spring.

I'm sure there must be pictures of one on the web somewhere. The trick is finding it...

Robert

[Winger Ed.]

I'd leave the old one in if its working right, and not worry about changing it unless ya needed to.

[Xringshooter]

I'd leave the old one in if its working right, and not worry about changing it unless ya needed to.

It's not that, I was given a bag full of springs and I want to figure out what the trigger pull on them are. Example, Wolff sells kits with 16#, 14#, and 12# trigger pull springs. How do they determine those weights? I know that if you know what metal it is, the diameter of the wire, the number of coils and the diameter of the coils there is probably a formula that tells you. I emailed Wolff but they never responded.

Also, the fact that they are compression springs (the hammer springs in a Security Six, et al) so I don't think you can just hang weights on one end - but I may be wrong.

[Shopdog]

Here's one I made for 1911 springs. Takes all of 5 seconds to check one. May jog an idea for you?

It mounts to the primer arm slot on the old T mag press. Have a few accessories that utilizes this slot(priming is done with hand tools).

[Winger Ed.]

It's not that, I was given a bag full of springs and I want to figure out what the trigger pull on them are. .

Oh. That's a bit of a headscratcher with out some specifications from the maker.

You could get a tube to drop them in, and start stacking weights--- but;
On those coil springs, there is preloaded compression length & tension when they are at rest in the gun,
and then more is loaded up on them as the hammer travels.

[jim147]

I've used spring pressure testers for years but they are two high a pressure for your need and would cost more then buying the spring you want. May be able to build one like above but would still take some work to be sensitive enough at lower pressure.

[uscra112]

Not to put too fine a point on it, but you are measuring spring RATE, not weight.

[imashooter2]

I don’t see an easy conversion to trigger pull weight from the weight required to reach some standard compression length. For instance, the Wolff 14 pound rebound spring for S&W revolvers does not give a 14 pound trigger pull, either with or without a mainspring installed.

[uscra112]

There obviously isn't. And when it comes to calibrating trigger pulls, the operative parameter will be preload, not rate, in any case.

[Winger Ed.]

You might could line up all the ones that look the same as far as length, wire size, number of coils.
Then test the batches with a simple tester to be sure they are the same.

Then you'd only need to put one of each group in the gun and check it with a trigger pull scale.

[Xringshooter]

Not to put too fine a point on it, but you are measuring spring RATE, not weight.

Correct, I just couldn't come up with the word. I am sure that Wolff, with it's resources, knows that x type of wire, of y diameter, coiled to z diameter with w # of coils with a certain complete length equals a cetain trigger pull in certain firearms.

I am 95% certain they are all OEM springs so the would probably test out at 16# trigger pull in the Six series revolvers. These were all taken out of guns over the years that were to be destroyed by a PD. The PD armorers were allowed to keep all the small parts because only the frame had to be destroyed. A guy I know was given these parts by a retired armorer from that PD and he sold me a massive number of Six series parts and these springs (at a very good price I may add - couldn't pass it up as I specialize in repairing/refurbishing these Rugers).

I'll probably, on a rainy day, take samples and test them in one of my Security Sixes and if they all test about the same , consider the bag of them that trigger pull weight. I have a tool that makes it easier to mount them on the mainspring strut so it's just taking the time to do it.

I do appreciate all the comments/hints/etc from all.

[uscra112]

Coil springs can be considered as a torsion bar, wound into a helix, if you can wrap your mind around the topology. The only factors which matter are the length of wire, it's diameter, and the modulus of elasticity of the metal.

Factors governing trigger letoff pressure have to include sear angles, sear depth of engagement, surface finish in the Hertzian (contact) zone, trigger spring resistance and probably half a dozen other things I'm forgetting. The engagement pressure on the sear from the hammer(striker) spring is only one factor.

Set up some sort of vertical rod onto which you can slip the spring to be measured for rate. Holding it a vise might to. Should be a foot long or thereabouts. Find or make a tubular weight that can be lowered onto the spring, heavy enough that it will compress the spring to about 1/4 of its' length, but without any coil bind if it progressively wound. Doesn't matter what the weight is, so long as you know it accurately. Measure the free length of the spring. Lower the weight onto the spring and measure how far the spring was compressed. The rest is simple arithmetic.

So very often I see it said that you can reduce a spring by shortening it. That can reduce the installed preload. Since you've reduced the length of wire in the spring, the rate actually goes up.

[wv109323]

The 1911 recoil spring and I ASSUME others no not follow mechanical engineering guidelines. The 1911 recoil spring is labeled as to the poundage that it takes to compress the spring to the minimal length in the firearm under recoil. This dimension in the 1911 is roughly 1 5/8". So the standard government 1911 spring takes 16 pounds of force to compress it to a length of 1 5/8". There is no preload or spring rate in the way gun springs are labeled.
You could take all like springs and compress them to the same length and sort by heavy and light. You would need a way to measure force to seperate.

[uscra112]

They may not specify by rate, but they can't evade physics.

You can calculate force required to compress to a specific length once you know the spring rate, determined as I described. Not rocket science.

The tubular weight provides a known force. Doesn't have to be more than a couple of pounds, so long as you know its' weight accurately. You don't have to compress to any specific length, so long as you can measure accurately.

[M-Tecs]

The basics of measuring spring rate

http://guntoters.com/blog/2020/01/10...tal-scale-kit/

https://www.shootingtimes.com/editor...weights/383919

https://www.1911forum.com/threads/spring-rates.3155/

https://www.eatondetroitspring.com/s...-vs-load-rate/

https://suspensionsecrets.co.uk/how-...-spring-rates/

https://raceland.com/news/how-are-sp...ates-measured/

[country gent]

The gauges we made for doing this used a scales. A bridge mount was made that fit over the scales and bolted to a plate. the height was about half the uncompressed spring length a hole bored thru it in the center of the cross bar just smaller than the spring od. a heavy weight from round stock was then turned up. the stem was a loose fit inside the spring and 1/2" short of scale pan. In use the spring was slid on the boss and inserted thru hole with the weight holding it to the height of the cross bar, Spring weight was then read on the scales.

[uscra112]

That tester based on an electronic tension scale looks cheap enough and will work. Clever.

https://www.securefirearmproducts.co...lno=11490-SR-D

[Xringshooter]

That tester based on an electronic tension scale looks cheap enough and will work. Clever.

https://www.securefirearmproducts.co...lno=11490-SR-D

Not a bad idea, I can measure a compressed OEM mainspring to use to get the initial distance and then take that spring off the mainspring strut and see what the meter indicates. Then just swap springs and see what they measure.

[contender1]

I have a spring tester. I haven't tried any Ruger Security series springs,, but you are welcome to try it in July,,,!