What evidence supports the claim that a dual recoil spring reduces recoil? - Page 2

What evidence supports the claim that a dual recoil spring reduces recoil?

This is a discussion on What evidence supports the claim that a dual recoil spring reduces recoil? within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; Originally Posted by Crowbait Tangle, In my mechanical/racing experience I think that most of it has to do with the progressive spring rates in each ...

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Thread: What evidence supports the claim that a dual recoil spring reduces recoil?

  1. #16
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    Quote Originally Posted by Crowbait View Post
    Tangle,
    In my mechanical/racing experience I think that most of it has to do with the progressive spring rates in each individual spring; the key term being "progressive". As you said it cannot reduce recoil it can only change felt recoil by altering the time/rate over which the force is applied. With dual springs there is much more leeway in using different rate spings because they can be tuned and "coupled". I personally think that a single spring can be just as effective as dual but that part of this whole thing has to do with the fact that technology sells.
    I apologize if this sounds a little discombobulated I'm under the weather and have a bit of a cloudy head from the drugs.

    -Russell
    Hey Russell,
    Hope you get better soon. I've had something myself.

    I'm not aware that dual recoil springs are progressive. They look to have a linear spring constant rather than progressive, where I'm using progressive to mean a changing spring rate along the length of the spring.
    --------------------------------------
    hmmm, here's something significant that needs to be addressed. When constant rate springs are combined as they are in a dual recoil spring, once they start working together, they act no differently that a single spring would with an equivalent spring constant. For example if one spring has a spring constant of 10 lbs/inch and the other is 5 lbs/inch, they would have a combined, linear spring constant of 15 lbs/inch. They'd be equivalent to a single spring with a spring constant of 15 lbs/inch and behave exactly the same.

    Just to be thorough, if you were to put the same to springs end to end instead of in 'parallel' they would have a combined, linear spring constant of 3.33 lbs/inch.

    Once the two springs start working together, they are no more than an equivalent of a single spring. They have the same characteristics.
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  2. #17
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    Quote Originally Posted by Tangle View Post
    Hey Russell,
    Hope you get better soon. I've had something myself.

    I'm not aware that dual recoil springs are progressive. They look to have a linear spring constant rather than progressive, where I'm using progressive to mean a changing spring rate along the length of the spring.
    --------------------------------------
    hmmm, here's something significant that needs to be addressed. When constant rate springs are combined as they are in a dual recoil spring, once they start working together, they act no differently that a single spring would with an equivalent spring constant. For example if one spring has a spring constant of 10 lbs/inch and the other is 5 lbs/inch, they would have a combined, linear spring constant of 15 lbs/inch. They'd be equivalent to a single spring with a spring constant of 15 lbs/inch and behave exactly the same.

    Just to be thorough, if you were to put the same to springs end to end instead of in 'parallel' they would have a combined, linear spring constant of 3.33 lbs/inch.

    Once the two springs start working together, they are no more than an equivalent of a single spring. They have the same characteristics.
    You make a good point...I just don't know.
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  3. #18
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    Eaglebeak, it doesn't work that way. The only property of a spring be it single or dual that can slow the slide down is the spring constant. To slow down the slide with a spring you'd have to increase the spring constant. But if you increase the spring constant and hence the force, the slide energy will be absorbed quicker and the slide will stop in a shorter distance. But then you can achieve that with either a dual or single spring. If you slow the slide down very much the slide won't travel far enough to fully extract the case or pick up the next round.
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  4. #19
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    I have tried the SPRINCO "recoil reduction" system in a Colt Commander. I bought it (more out of curiousity) on Ebay because it was brand new & the price was right.

    I think I paid $35.00 & shipping for it. It is beautifully well constructed.

    The SPRINCO has an extremely stiff secondary spring that kicks in before the slide fully slams to the rear.
    So it does reduce that felt "slide to frame" impact and the recoil impulse definitely feels different.

    Spent case ejection is "normal" because that action happens before the secondary spring begins to compress.
    I have used one and muzzle rise is somewhat reduced though I have no explanation as to why.

    The SPRINCO is not without it's idiosyncratic problems though. It needs fairly HOT ammo in order to function flawlessly....and it's very difficult to manually lock the slide to the rear.
    I can do it but, others who have tried to manually lock the slide to the rear have not been physically able to accomplish the task.

    All of the above having been said...I own that one for the Commander but, I don't use it. It's sitting in a drawer.

    So....Tangle ~ if you have access to a Commander & want to goof around with it then you're more than welcome to experiment with it. Just let me know.

  5. #20
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    Tangle you might think this article is interesting. Take it for what it's worth.

    June, 96 Recoil
    I am using a vintage (no longer being made) Harrt's installed in my P220 because I can tell that it will get me back on target a bit quicker during rapid fire.

  6. #21
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    I think everyone's got it--you can design the system to alter the profile of the curve (velocity of the system vs time), the area under the curve remains the same. The exception was suggested already--losses (spring system friction was mentioned). Another way to alter both the shape and area under the curve would be thru use of dampening (i.e., shock absorber), and I think there's a product out there.

    That brings us to 'perceived'. All I have to do to improve your perception of a product might be to raise its price. You could publish the curves in your ad, showing how the product is changing something, and say it's 'recoil'. Sold! We're talking perceived here--if you charge enough for the product, folks will swear they feel the difference whether there is one or not. Sort of like how a Magic Polymer frame reduces recoil. If the frame doesn't get hot after firing 10 rounds, it's not 'absorbing' anything. It's just another spring, albeit a very stiff one. If it feels better, then shoot it!

    But, with multiple springs or contoured (e.g., progressive) springs, etc., you already know the impulse profile, if you will, is changed. The evidence I think you want is the actual curves, before and after (stock vs modified) to see how much difference there is. But still, that won't tell you if that difference is perceived by the average person. It will only tell you if there's a measurable difference.

    What I THINK really happens is that Marketing and Advertising people write the ad copy. While the engineers in Engineering will stomp and spit all day long telling their sales friends to say "perceived recoil" or "felt recoil", the distinction is lost when it comes to the folks who pay their mortgages by moving product. They are likely to argue that by definition 'recoil' is 'perceived recoil', so what's the big deal?

    The use of different, multiple springs definitely will change the impulse profile, and some folks may perceive reduced recoil. The reality of it all can only be tested through a blind test, suggested above. That would be fun to do.
    Last edited by Bongo Boy; January 27th, 2012 at 06:09 PM.
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  7. #22
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    I did a blind test with coke one time and I liked the Pepsi better. Some people over think, to try and reduce felt recoil is in the way you hold the gun and transfer the energy. I think making a super spring is a selling point. Recoil management is a better answer; learning to control recoil is a better way to go because a 357 revolver has no double spring in it

  8. #23
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    The Harrt's actually does "eat up" some energy that is expended in the fracturing of the liquid Mercury metal & that happens right at the instant of cartridge detonation so it works on an entirely different principle than an added secondary recoil spring.

    I know that it does allow the muzzle to come back down on target in a bit more of a hurry.
    I believe that it does have some real advantage though it is certainly not any sort of 40% or 50% reduction of anything.
    I would best guess 15~20% max but, with no function related disadvantages AKA there is nothing "mechanical" to ever break.
    The Mercury just stays forever sealed up inside the Stainless recoil spring guide.
    I've had it installed in my SIG firearm for many years now.



    "The Harrt’s Recoil Reducer was simple and well made, showing no outward flaws in workmanship. It relies on a reciprocating mass made up of mercury and ball bearings enclosed in the rod to dampen recoil.
    Essentially, the mercury and ball bearings provide inertia that lower the rearward recoil of the pistol.
    The Harrt’s device weighs about 2 ounces, and the heavy liquid mass encased in the rod tries to remain stationary as the gun begins its recoil cycle and adds forward mass after its inertia is overcome.
    It has no means of being rebuilt, but examining units that have been used by competitive shooters for two years show,
    I’ve seen little wear or peening where it is hit by the slide. To install it, you simply remove the original guide, spring, and recoil spring cap, replace the guide with the Recoil Reducer rod, replace the slide on the frame, and reinstall the recoil spring and proprietary cap supplied by Harrt’s.
    The assembly is then anchored as normal with the barrel bushing. It was easy and straightforward to install the Harrt’s product."

    Here is one cut open so...imagine it also filled with Mecury metal.

  9. #24
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    Sheez, I'm so lost now. Who cares how it works as long as it does.
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  10. #25
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    Quote Originally Posted by Tangle View Post
    I am an engineer. I know what you're saying, but the same amount of energy and momentum has to be absorbed by the hand.
    Agreed.

    I'm a bit uncertain about exactly what you are referring to as a DRS. Here's what I'm thinking. Situation 1) I have a Colt Mustang which initially had two springs, coiled about each other. When one of the two broke it was replaced by a Wolf Spring--single "leaf" if you would; and really there was no felt difference IMO. In this instance the overall length that the spring had to be compresses was constant, and I assume the Wolf Spring allowed the same (or very nearly so) velocity, hence no difference felt.

    Situation 2) I have another gun in which the springs are arranged entirely differently. What I think they have achieved is an approximate doubling of the spring length by the way the springs move counter to each other within one "container."

    This is where I think maybe your analysis is not quite 100%. "But a spring cannot provide additional movement." That depends on how the double spring is arranged.

    I'll guess they do that to allow for compact construction, not so much for reducing recoil. But my point is, anything done in the engineering which effectively increases the length of the spring slows the travel velocity of the slide a tad, and would have a dramatic effect on impact; due to the v ^2 business.

    Now since you and Gasmitty are the engineers, and I'm just playing one on the net, I'd better shut up.
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  11. #26
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    Quote Originally Posted by OldVet View Post
    Sheez, I'm so lost now. Who cares how it works as long as it does.
    That's kind of the point--sometimes you can't really know if something works unless you understand how it works. This is almost always the case when the benefit is so small as to be a matter of opinion, which in turn is almost always the case with 'magic' products. They work far more on Faith than they do on Physics.

    The Hartts device is a hydraulic damper, and if the change in the motion of the gun is measurable using lab equipment, I'd be surprised. Very surprised.
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  12. #27
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    Two concentric springs will act as one unless progressive magic (helical winding or variations in wire diameter) is involved. Due to the law of conservation of momentum, total recoil momentum will always equal MV of the bullet. Some of the recoil momentum will be spread out in time until the slide hits the frame, and that can alter subjectively perceived recoil. Perception is an engineer's nightmare and a marketer's dream. As spring force increases while it slows down the slide, it accelerates the frame with a smooth quadratic curve during the elastic phase of recoil. The inelastic collision as the slide hits the frame, imparting the residual momentum, is what I think most perceive as recoil. The stronger the spring, or combination of springs, and the longer the distance over which the spring acts, the more time it takes to bleed off momentum. Little balls in mercury will continue to bleed off momentum, even after slide stop, but not much.

    That's just the theory. Double springs shouldn't affect perceived recoil enough to be perceived.

    In the lab, theory is just the starting place. We fiddle and screw with stuff until something works, then we do the math to justify it. I'm guessing the gun designers found a production spring that came close, and then they fine tuned it with a smaller production spring until it cycled OK, picked up a new round, and didn't beat up the frame to badly. But I wasn't there.

    In theory, a 3" slide can't bleed off as much momentum as a heavier 5" slide that can travel longer. But the shorter barrel can't generate as much velocity either. So, It's just as much fun shooting my Gold Cup as my Ultra. Can I do the testing for you?
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  13. #28
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    I still don't think the original reason for the DRS was reduced felt recoil. I still believe it was for a fix of reliability uses when using a WML or other attachment. The percieved less felt recoil was a byproduct that someone said they noticed, and now has become an "added " marketing benefit. And that is all.
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  14. #29
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    Quote Originally Posted by glockman10mm View Post
    I still don't think the original reason for the DRS was reduced felt recoil. I still believe it was for a fix of reliability uses when using a WML or other attachment. The percieved less felt recoil was a byproduct that someone said they noticed, and now has become an "added " marketing benefit. And that is all.
    This is what I heard too, I believe it was the G22's that were having the problems when using WML's.

    I have to agree with Tangle, as long as the weights were the same on the RSA's, why would it being a dual or a single make a difference? The only thing I have ever personally experienced when dealing with RSA's is that a stiffer spring helps with muzzle jump. Slide meets more resistance, which means less energy slamming the gun upwards when the slide impacts the frame, the force reaching your hand is the same, just directed differently.
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  15. #30
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    I believe the enlarged diameter of the spring assembly gives better stability to the slide, which inturn fixed the problem of frame flex during recoil malfunctions using the WML. It doesn't have anything to do with rearward tension or stiffness, but overall stability, ie.. larger surface area of tension.

    But hell, Im not very smart, so that's just a guess.
    Ignorance is a long way from stupid, but left unchecked, can get there real fast.

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