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

The claims that a dual recoil spring (DRS) reduces recoil (compared to a single spring) seem to come from gun magazines and subjective impressions. Then these unsupported claims get parroted until they are assumed to be factual. Have there been any blind tests that concludes anything or have there been any tests at all?

From an engineering perspective, this claim is questionable. The simple purpose of the recoil spring is to decelerate the slide to a stop and then return it to the closed position. Since the energy imparted to the slide is fixed, i.e. controlled by the mass and energy of the bullet, AND the distance the slide has to stop in without dead-ending on the frame is also fixed, a DRS has to absorb the very same energy, motion, and velocity in the very same distance as a single spring does.

The only thing a DRS can do is change the velocity profile of the slide. E.g. a DRS can have a weaker spring weight to start with (as in the GLock gen 4 DRS) but then somewhere along the slide travel rearward, the spring rate has to increase to a much higher rate so that the average force of the spring over the distance the slide travels is essentially the same as a single spring.

Now, it's clear to me that this may provide a desirable operational or functional characteristic, like letting the slide open a bit quicker, but in no way does it suggest that a DRS either increases or decreases recoil. For a given load, the recoil energy is constant and dependent on the mass and energy of the bullet. Either the single spring or a DRS has to absorb that energy.

The recoil profile will be modified, but again, the math doesn't support whether the changed profile will feel like more or less recoil.

So why do we keep hearing a dual recoil spring reduces the felt recoil? If it really did, doesn't it seem odd that the majority of manufacturers use single recoil springs?

Tangle, your engineering sense is showing. You're absolutely correct that the spring or springs can't reduce recoil. I think you're on target with the dual springs changing the veloicty profile which could result in a perception of lower recoil.

But to a non-scientific market of buyers, "dual springs reduces recoil" becomes an accepted rationale. Remember STP made millions with a non-scientific marketing mantra that sounded technical enough for the unwashed masses, but didn't hold up to scientific scrutiny.

The Glock subcompacts have had dual recoil springs since inception in 1995. Felt recoil in a Glock 26 is softer than a Glock 19. Doesn't really reduce the recoil, but cushions the recoil...kinda like shock absorbers on your car. Ask anyone that has owned a Glock subcompact and a mid size or full size, and they will tell pretty much the same story.

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Originally Posted by gasmitty

Tangle, your engineering sense is showing. You're absolutely correct that the spring or springs can't reduce recoil. I think you're on target with the dual springs changing the veloicty profile which could result in a perception of lower recoil.

But to a non-scientific market of buyers, "dual springs reduces recoil" becomes an accepted rationale. Remember STP made millions with a non-scientific marketing mantra that sounded technical enough for the unwashed masses, but didn't hold up to scientific scrutiny.

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You're a wise man gasmitty.

I'd love to do some 'blind' tests just to see if a large number of shooters could tell a difference one way or another.

What I'd like to do is set up a test and tell each participant that I have three guns, say three G-22s, and I want them to tell me which has the softer recoil. Of course one gun would have a single recoil spring (SRS), another a DRS, and the other, a different weight SRS. I'd also tell them that it's also possible that they might get the same gun three times instead of three different guns.

I thought the main reason they went to the DRS was because of reliability issues when the full size models were used with a WML? And the percieved lower recoil was touted as a beneficial side effect of said change.

Just a guess, as I'm not a physicist or engineer. "Impact" may be confused here with recoil. The impact of the gun against the hand might be lessened by the dual spring. An inelastic collision (within the gun) gets changed to an elastic collision by the springs.

impact kinetic energy (1/2 mv^2)

A slight slowing of the collision of slide with slide stop will translate to less "impact" at the wrist-- less felt recoil. That is the same reason pliant grips reduce felt recoil. They are elastic and reduce impact. It is a matter of altering the impact, not altering the total momentum of the recoil which is fixed at the velocity of the projectile X its weight as m*v.

Above clearly an uneducated guess and I'm sure we have plenty of engineers and such here to address this.

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Originally Posted by zonker1986

The Glock subcompacts have had dual recoil springs since inception in 1995. Felt recoil in a Glock 26 is softer than a Glock 19. Doesn't really reduce the recoil, but cushions the recoil...kinda like shock absorbers on your car. Ask anyone that has owned a Glock subcompact and a mid size or full size, and they will tell pretty much the same story.

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Yeah, but that's a totally different comparison. The gun proportions have changed, with different length barrels, with different bullet velocities, and hence different kinetic energy transferred to the slide and gun; the mass of the slides are different.

It would be interesting to compare a G26 to a G19 gen 4 since it has a DRS. I doubt it'd be any different than a gen 3 26 and 19 though.

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Originally Posted by glockman10mm

I thought the main reason they went to the DRS was because of reliability issues when the full size models were used with a WML? And the percieved lower recoil was touted as a beneficial side effect of said change.

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I think the DRS is for something totally other than felt recoil. They may claim a reduced felt recoil; if they do, I'd question the claim until I saw the test data to support the claim.

I would figure "felt" recoil would be a combination of force and time. A small force for a very short time would be perceived as a harsh recoil. Whereas a large force over a longer time would be perceived as a soft recoil. Springs spread the force over a longer period of time, hence less perceived recoil. Then again, I could be completely wrong.

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Originally Posted by Hopyard

Just a guess, as I'm not a physicist or engineer. "Impact" may be confused here with recoil. The impact of the gun against the hand might be lessened by the dual spring. An inelastic collision (within the gun) gets changed to an elastic collision by the springs.

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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. A single recoil spring will produce a steadily increasing rearward force, hence impact on the hand. A DRS can modify how the force is applied. If it reduces the force one place over a certain distance, it has to dramatically increase the force for the remaining distance so the same amount of energy and momentum is absorbed.

OTOH, maybe the additional mass of the DRS decreases recoil. But if that's the case a SS guide rod would accomplish the same thing with a SRS. So it's really not the spring, it's the mass in this case.

And there could be something we're not taking into account somehow. In the case of a dual rate, dual recoil spring, maybe the DRS has more friction and absorbs some of the energy. Maybe the DRS allows the slide to unlock faster and who knows if that might help or not.

But what I'm looking for is evidence. I just want to know how we 'know' I guess.

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Originally Posted by Hopyard

...A slight slowing of the collision of slide with slide stop will translate to less "impact" at the wrist-- less felt recoil.

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The slide could be slightly slowed by a slight stronger single spring.

The problem with impact is that it's dependent on the bullet energy and momentum that's imparted to the slide from firing the bullet. Slowing the slide would require a heavier spring. You can accomplish that with either a single or dual spring.

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Originally Posted by Hopyard

...That is the same reason pliant grips reduce felt recoil. They are elastic and reduce impact. It is a matter of altering the impact, not altering the total momentum of the recoil which is fixed at the velocity of the projectile X its weight as m*v.

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Not quite. The compliant grip allows additional movement of the gun - that increases the distance and time the hand has to absorb the recoil. But a spring cannot provide additional movement.

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Originally Posted by RKflorida

I would figure "felt" recoil would be a combination of force and time. A small force for a very short time would be perceived as a harsh recoil. Whereas a large force over a longer time would be perceived as a soft recoil. Springs spread the force over a longer period of time, hence less perceived recoil. Then again, I could be completely wrong.

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Well, I asked for evidence. What we've all submitted is theories with no support behind it.

RK,
You've hit on the idea. I don't know that I can agree with your conclusions. But what you described is exactly what a DRS does. It's a lighter force over a certain distance followed by a heavier force over the remaining distance. I think the average force would be the same as a single recoil spring.

And guys, we may be being 'sucked' in by manufacturers claims about DRS reducing recoil. If it is true that they do even by as little as 0.5% then manufacturers can claim reduced recoil. There's no way on earth a human could sense or feel that small of a difference.

BTW, I'm not saying it doesn't, I'm asking what evidence do we have that it does and I think as a part of that, by how much?

I'd like to see the time it takes for a slide to make a complete cycle in a pistol with first a single spring and then a dual spring. Could be just the smoothing effect of spreading out the entire felt recoil effect over a different length of time.



bosco

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Originally Posted by boscobeans

I'd like to see the time it takes for a slide to make a complete cycle in a pistol with first a single spring and then a dual spring. Could be just the smoothing effect of spreading out the entire felt recoil effect over a different length of time

bosco

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But couldn't we adjust a single spring to give us the same time as a DRS?

I'm just asking guys. I'm curious how we 'know' a DRS reduces recoil and by how much.

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

In the reality of physics, the only things that can actually "reduce" the recoil force of a standard, closed-breech weapon are to either increase the weight of the weapon, decrease the weight of the bullet/projectiles, or decrease the propellant charge.

"Apple-knocker" Newton's law brushes the surface by starting out with "any action will generate an equal and opposite reaction" which simply means that generation of a sudden explosive force that is confined between two objects (propellant ignition between bullet and weapon) will apply an equal force against both objects that tends to push them away from each other in opposite directions with the same degree of force.

Obviously, there are other physics principles involved or your .44 magnum handgun would come smashing back through your body at 750fps while the bullet went in the other direction at 750fps at a total of 1500fps velocity of their departure away from each other. What keeps that from happening is mass/inertia physics which involve only the "inertia of rest" when considering recoil force. The rule there generally states "an object at rest will tend to remain at rest and resist any force to set it in motion with an opposing force that is directly proportional to the mass (weight) of the object". You can quickly test that law by forcefully kicking a soccer ball and see how far it flies away - now, deliver the same forceful kick to a bowling ball and note which one of them resists being moved with such a force that it will break your toes and only move a few inches at best.

Since the broken toes after kicking the bowling ball are an indication of an "equal and opposing force" that are directly proportional to mass/inertia, consider the ratio between the bullet's weight and the weight of the weapon when the same force is applied between them. Obviously, the weapon's much higher weight and inertia of rest will instantly oppose the force trying to move it which, in turn, re-directs that force against the much lighter bullet to send it flying away at 1500fps while the much heavier weapon only moves to the rear at a few thousand times less speed and force.

Making the weapon heavier or making the bullet lighter will reduce the recoil force even more because the ratio of weapon weight/mass to bullet/mass has increased. Using a heavier bullet or decreasing weapon weight will reduce the mass/weight ratio between weapon and bullet which will result in more recoil force. Increasing or decreasing the propellant charge is a no-brainer on recoil changes since there's more or less force being generated.

After considering the physics laws of actual recoil force as being a "constant" with any particular weapon using the same weight bullet and same propellent force, there is nothing that can further reduce the level of that force. However, the effects or "feeling" of that recoil force CAN be reduced by spreading its application out over a longer period of time. Consider laying on the floor with a box on your chest while someone on top of a 6' step ladder drops a 50-pound bag of sand into the box (major owwieeee, broken ribs, etc.). Now consider that same person slowly pouring that bag of sand into the box on your chest; even though you're still taking the same amount of total weight or force against you, it's being applied at a much slower rate which does reduce the "feel" (and even injury) over it being applied all at once.

Dual springs, recoil pads, and all other such "recoil suppression" devices don't actually reduce the amount of recoil force in itself; but they do make that same amount of recoil force considerably more comfortable and manageable by spreading its application over a longer period of time.