Recoil Spring Study

There's been a rash of discussions on recoil springs lately. The prevailing question seems to be: "What is the best/correct spring rate for ammunition X in 1911-pattern gun Y" and the concerns are with frame damage. It rarely comes up in a discussion on any other platform.

The generally accepted line of thought is that The Commanders and Officer's Models require heavier springs because the faster slides hit the frame harder... and that without the added deceleration afforded by the heavier springs, the frames will be quickly beaten into junk.

*cough*

Somewhere along the line, we were told these things, and because it made sense... we readily accepted it. The problem is that it's not based in fact. It's based either in opinion... or it's based on the "Dog in the Fight" theory from people who make money selling springs and such amenities the familiar shock buffer.

If... and this is a big "IF" for many people who can't let go of the energy mindset... if we accept that momentum is the factor that does damage in any impact event, we can take the argument apart and discover the truth. The key lies in Newtonian physics. Good ol' Isaac to the rescue again.

In Newton's 3rd Law of action and reaction, we know that there must also be equal momentums on both sides of the system. Simply put, the slide's momentum can't be greater than the bullet's... but equal momentum only exists in the absence of outside force, or in the presence of equal outside force.

The Commander slide is faster with a given ammunition than the 5-inch gun's slide... but it hits the frame no harder... because the momentums must be the same. Lower mass requires greater speed to achieve equal momentum... all else assumed to be equal.

The slide's momentum can't be greater than the bullet's. Straight up can't happen. Let that simmer a while.

The shorter barrel of the Commander produces less bullet velocity, and because momentum is a function of Mass X Velocity... less bullet momentum. Less bullet momentum means less slide momentum... because the two are equal with equal springs and equal ammunition.

And another aspect is that, the lower the mass of the moving object, the faster its deceleration rate whenever it encounters a given outside (resistive) force. So, even with equal springs and ammunition...the Commander slide doesn't hit the frame quite as hard as the 5-inch slide.

I'm fairly certain that Colt's engineers are aware of these things... yet they use heavier springs in the short pistols. It seems that's backward thinking. If the momentum is lower, and the impact stresses are less... why not use a lighter spring? The slide needs a certain level of momentum to complete the trip backward. Installing a heavier spring would seem to compromise that... yet they do it.

Why?

Because the "Recoil" spring's function is in accelerating the slide forward... not decelerating it. The less massive slide requires extra speed to achieve the momentum needed for a reliable return to battery. After all... the resistive forces on the slide when it's moving forward are pretty much identical in both guns, and those resistive forces have to be overcome.

Before the energy question comes up, take a look at energy vs momentum as the destructive force.

Compare the 5.56/M193 cartridge to the original .45-70 "Cavalry" load.

55 grains at 3250 fps vs 405 grains at 1300 fps. There is little difference in the respective muzzle energies. Yet, the .45-70 slug will drive through a bull Elk lengthwise, while the .22-caliber pill probably won't get past the heavy chest muscles. Momentum.

Consider the loaded semi at 60 mph that nearly takes an abutment out from under a bridge while the Ferarri at 150 splatters like a bug on a windshield. Momentum.

Holding on by the fingernails

I think I have a glimmer of understanding what you have said. Can't quite get my head wraped around it 'tho.

My Colt OM from Hades was oversprung, and some gent clipped a few coils off each spring. Other things were addressed also. That was a few years ago. Me and the OM continue to play nice with one another. Whoever that masked man was, I remain grateful. That was a clipped spring short slide and it hasn't self-destructed yet.

Back to the need (real or imagined) of a spiffier spring. If what you suggest is the unvarnished gospel, why the stouter spring in the 10mms?

Tuner, are the stock commander and Gov't recoil springs the same length?

Quote:If what you suggest is the unvarnished gospel, why the stouter spring in the 10mms?

A few reasons for that, Salty... and the gent only clipped the inner spring on that OMFH, as I recall.

The 1911 was designed around the .45 ACP cartridge and the stresses that it imposes. When somebody had the bright idea to chamber it for the Big10...they had to take that into account... because everything means something. While the frame isn't a huge concern with the velocity/pressure/impact momentum with the original cartridge... when we push the envelope with nearly double the stresses of the original... we have to take steps to try to hold the effects as close to what the pistol was intended to withstand.

Ned Christiansen solved the problem by using shock buffers in back-to-back tests firing 500 rounds with the DE in stock form, and then with his system consisting of a 25-pound mainspring... 18-pound recoil spring... and a very small radius on the bottom of the firing pin stop... and observing the damage done to the buffer. His system matched the original setup, and... if memory serves me... he even stated that it damaged it a little less with his way.

I'll expound a little on what you're havin' trouble with.

Momentum is the product of Mass X Velocity. I'll call mass "weight" to keep it simple.

When the weight of slide A is lower than the weight of slide B, firing the same ammunition, slide A will accelerate to a higher speed than slide B...even with the same bullet velocity. But... even though slide A's speed is higher, its momentum is the same. for both slides... hence the impact is the same for both, in spite of the lighter one impacting at a higher speed.

And... The slide's momentum is the same as the bullet's momentum, regardless of how fast the slide is moving. It can't be greater. So, the fast, light slide hits the frame no harder than the slow, heavy slide even with equal spring rates.

1K... No. Colt GM springs are 32 coils of .043 diameter wire. Commander springs are 22.5 coils of .043 diameter wire, with slightly wider spacing between coils for a higher rate which makes for a slightly stiffer spring. It's not 18 pounds at full compression as installed though, unless Colt has changed things since I last tested one. The GM springs generally run to about 14.5 pounds installed/compressed and the Commanders around 16.5 or so.

But you have not told me how to spring the 1911 so that frame impact is negligible and the return to battery is fast and does not disturb sight picture.

That'll take a little time and playin' with springs, RC. Not somethin' that I have time nor the inclination to mess with. Check Brian Enos' forum if it's still up. Those boys have it nailed down.

I think I remember Larry Brown sayin' somethin' about a 10-pound spring and double shock buffs in his .40 caliber game gun... but don't hold me to it. It's been a couple years.

One thought. Part of the return momentum in a 1911 is the residue of the backward momentum returned to the slide when it bounces off the frame (actually off the recoil spring guide). It is that "bounce", not just the recoil spring, that helps feed the next round and return the slide to battery, and it is due to the elasticity of steel. But alloy frames have much less elasticity, and absorb more of the backward momentum rather than returning it for the forward movement.

Shock buffers absorb even more energy, which is why feeding is sometimes impaired when a buffer is installed. The idea that all the rearward momentum somehow goes away when the slide stops its rearward travel just isn't true; remember those little racks with hanging ball bearings? Yes, folks, steel is elastic and the "bounce" off the frame is a big factor in the functioning of the 1911. So, without the "bounce", a stronger spring is required to ensure positive feed and return to battery.

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The idea that all the rearward momentum somehow goes away when the slide stops its rearward travel just isn't true;

Have you ever fired a 1911 without a recoil spring installed? I tried it after a Tuner thread a while back... I saw no bounce back forward. Not saying that you are wrong, but I had to try it after this conversation came up before. If there is any it appears to me to be negligible.

I believe, from what I saw in the few rounds I fired that way, that my arm is absorbing any of the energy that would have been used for a "bounce".

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The Commander slide is faster with a given ammunition than the 5-inch gun's slide... but it hits the frame no harder... because the momentums must be the same.

The momentums are the same, but (although I haven't done the math) I strongly suspect that the Commander slide will have more energy since it's moving faster and it isn't that much lighter.

Since slide impact force can be determined by dividing the slide energy by the distance that is required to decelerate the slide to zero, the impact force is greater for the commander slide than for the standard slide assuming that the commander slide has more energy and is decelerated to zero over the same distance.

The latter assumption is reasonable since both slides are pretty much stopped nearly instantaneously upon impacting the frame.

With the slide velocities and weights for both guns you can calculate more or less what the difference in the force applied to the frame by each will be.

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I strongly suspect that the Commander slide will have more energy since it's moving faster and it isn't that much lighter.

Sure it will, but energy isn't the damaging force. Momentum is. The concern with slide to frame impact is rearward peening and deformation of the impact abutment. Go back to the M193/.45-70 comparison and think about it.

If you're inclined to do the math, it'll be tricky because you'll need to know the slide velocities without the springs installed... but you can make a comparison by using estimated velocities. I suspect that you won't find a lot of difference, though. If you look at the estimated average velocities of a 230-grain bullet from both... 830 and 790 respectively... or about what you can expect between a 5-inch barrel and a 4.25-inch barrel... the energy figures come up to 351 and 318 ft lbs respectively. It can vary that much from one round to the next in the same gun.

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The idea that all the rearward momentum somehow goes away when the slide stops its rearward travel just isn't true.

No, it doesn't go away. It transfers to the frame, which then transfers it to the hand and arm, and so on. There is some rebound effect. Everything means something... but is it enough to make the difference in a successful return to battery? I gots me doubts. Now, if you were to mount the pistol in a heavy vise...

Rifleman... When you fired it sans recoil spring... the "recoil" was surprisingly soft. No?

Kinda shoots a hole in the theory that going to a heavier spring reduces felt recoil.

Just a few casual thoughts on the 1911 spring thing.

When somebody buys a Browning High Power or a Glock or a Sig, etc. they don't give it much thought. They figure that the engineers know their business and leave it alone for the most part.

Let'em buy a 1911, and right away... they feel like the engineers don't know squat, and they immediately start dinkin' with it.

Amusing.

Reminds me of my reckless, misspent youth..."improving" my car of the month, makin' it "better" and my father askin' me what made me think that I knew more about that car than the people who engineered it.

And he was right. Seems that whenever I made a little gain, I also lost something in the process... and it wasn't in direct proportion to the "improvement."

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Rifleman...When you fired it sans recoil spring...the "recoil" was surprisingly soft. No?

Yes. That's what caused me to try it. I read a post from you claiming that and I absolutely thought it was nuts. I figured it would kick like a mule. Nope.

I've had to completely abandon everything I thought I knew about 1911's and start over. I just rebuilt my Delta using this information and it shoots better than ever; with a 16.5 pound recoil spring, sharper radius FP stop, and heavy mainspring.

Congratulations, TR. You've discovered the secret to taming the Big Ten.

I believe I'd go with an 18 pound spring if you plan to shoot full-power ammo exclusively, as per Christiansen's system.

He's experimented with the 10 extensively and that's what he finally settled on. Although slide to frame impact isn't nearly the concern that it's made out to be... it's still a consideration.

I pretty much only shoot my reloads, which just barely make IPSC Major, in this Delta. So I think 16.5 is OK? I have heavier if you think I need to.

I did shoot 10mm Blazer in my testing, it's not full power 10mm either but stronger than my reloads. In fact I don't know anyone who makes full power 10mm these days.

I have a Dan Wesson Razorback I'll probably do the same treatment to and go heavier with the recoil spring on that one, I shoot heavier loads and sometimes carry Silvertips in it. Silvertips are not full power either.

So here's a question, since we're talking about it sort of. I assume that a 10mm just barely Major load still hits the gun "harder" than a .45 ACP just barely Major load since the bullet is lighter and the recoil snappier?

Then 16.5 should be fine.

Power factor is based on momentum, so it shouldn't hit the frame any harder than a .45 that makes the same power factor.

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"Let'em buy a 1911, and right away... they feel like the engineers don't know squat, and they immediately start dinkin' with it. Amusing."

+1 on that, Tuner. But then the 1911 is not a pistol, it is a cottage industry, like the Ar-15 and the Ruger 10/22.

Actually, Newton's Third Law of Motion isn't about momentum.

It states that FORCE is equal, opposite, and collinear.

And please don't say that force and momentum are the same thing. They aren't.

This doesn't poison Tuner's argument, it's just correcting a misstated assumption.

Tuner can continue with his discussion, he should simply clean up the way it's stated.

For the sake of accuracy, of course, and to avoid rebuttal.

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Sure it will, but energy isn't the damaging force. Momentum is.

Energy is the potential to do work/cause damage and is proportional to the force applied by the impact. The amount of impact force would seem to have a significant bearing on damage.

It's not possible to say that momentum doesn't play a part, (I'm certainly not trying to make a case to support an assertion like that), but, on the other hand, completely discounting energy as "the damaging force" isn't really consistent with the definition of energy and force.

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...energy figures come up to 351 and 318 ft lbs respectively.

You'd need to know the kinetic energy of the slide. For that you'd need to know the slide weight and slide velocity.

If you can give me the combined slide/barrel weights for each gun, and the muzzle velocity and weight of the bullets for the load in question, I can calculate the slide velocities (neglecting the recoil spring) and from that I can calculate the two slide energies for comparison.

ants... I know, and I'd never say that. I'm using Newton 3 and equal momentums for illustrations. We can muddy this thing up with in-depth discussions of the finer points of Newtonian physics... but I'd like to avoid that if I can.

John... You just can't let go of the energy thing.

Slide to frame impact is essentially a straight-line crash. The damage... if there is any... comes from the frame abutment being peened back. Like the semi/bridge abutment point... mass and momentum are the factors that try to drive the rig through the abutment. The Ferrari hits with high energy, and while it'll knock a few chunks of the concrete off, it won't do a lot of structural damage to the abutment. The semi will.

It's the same reason that Karate students are taught to punch at the spine instead of the sternum... to think of driving their fist through the chest rather than at the surface.

A boxer's sharp, quick (high velocity) left jab may strike with stinging energy... but it's the right cross... with the weight of the upper body behind it... that does the real damage.

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I don't know what this means. It's sort of like starting a discussion about what 6 times 9 is and then accusing one of the participants of not being able to let go of the multiplication thing.

You started a discussion about impact damage potential. Assuming roughly similar material properties of the two colliding objects, then the impact force would be proportional to the energy of the moving object divided by the distance it takes to stop the moving object. Since, in the absence of a recoil spring, the distance required to decelerate the two slides to zero is essentially identical, you can get a good feel for the difference between the two impact forces by calculating the two slide energies.

Since you mentioned that you were concerned with whether or not the Commander slide "hit the frame harder..." which sounds a lot like impact force, I'm pretty sure that you do believe that impact force is a factor in potential damage to the frame or slide.

Which makes me think that you're saying that you don't believe it's possible to calculate impact force in the manner I describe. Is that right?

John, instead of continuing to argue small physics details, I guess it's time to get to the bottom line... which is just this:

The notion that the Commander and Officer's Model require a heavier spring than the GM to prevent frame damage is unfounded and a bit absurd. The two are so close in impact energy and momentum that any difference wouldn't amount to a stack of corn bread... even with an equal spring rate. Its not there. The 1911's frame just isn't that fragile. If it were, they'd never stand up to the tens of thousands of rounds that some shooters subject them to...with any reasonable spring rate. The slide and barrel take the real pounding anyway... not the frame.

When I first heard those warnings of frame destruction, I was a little puzzled, and then I started to look at it as another "Sky is Falling" rumor.

When the US Army adopted the 1911, and again with the A1 contracts... probably a dozen slides and barrels were ordered for each complete pistol... along with many dozens of various small parts. The frames in those days weren't hardened. The clues are evident. They knew that the frames would endure.

As with the action spring in any other self-loading arm, the "recoil" spring's only function is returning the slide/bolt. Whatever else it does is incidental and essentially irrelevant.

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If it were, they'd never stand up to the tens of thousands of rounds that some shooters subject them to... with any reasonable spring rate.

That doesn't necessarily follow.

Good quality steel has an endurance fatigue limit and unless that fatigue limit is exceeded (or the object is defective in some way), it doesn't matter how many impacts the steel object suffers, it won't fail. In other words, the fact that a steel object lasts for 50K impacts at a particular impact level doesn't imply that it will last for even 500 impacts at a greater impact level if the greater impact is sufficient to exceed the steel fatigue limit.

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The two are so close in impact energy...

From what I can tell, a standard 1911 barrel & slide have a combined weight of about 18oz and a Commander slide & barrel weigh about 3 oz less.

To find the slide velocity, I'll use these figures from an earlier post on this thread:

"230-grain bullet from both... 830 and 790 respectively... or about what you can expect between a 5-inch barrel and a 4.25-inch barrel..."

I neglected the momentum of the gases as it should be identical for all practical purposes.

Using conservation of momentum, that provides slide velocities of 24.2fps and 27.7fps.

Using 12.6oz for the weight of the standard slide and 10.5oz for the lighter slide, the impact energy can be calculated (neglecting the spring). The lighter slide hits the frame with about 9% higher impact energy and therefore about 9% more impact force if we assume both slides are stopped in the same amount of distance.

9% is not a huge difference, but it's not what I would call negligible.

If someone can provide more accurate weights for standard and commander slides and barrels I'll redo the calculations with the correct figures.

John... Ask yourself a logical question.

If frame impact is such a concern...

Why doesn't Colt install an even heavier spring in the LW Commander than in the Combat Commander? Aside from the frame material, the guns are twins.

Why?

Because decelerating the slide isn't the spring's function. Never has been.

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Why doesn't Colt install an even heavier spring in the LW Commander than in the Combat Commander? Aside from the frame material, the guns are twins.

If the uppers are identical then the slide velocities would be identical as well. If the stronger spring is to ameliorate the effects of higher slide velocity then logically two guns with identical slide velocities would get the same weight springs.

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Because decelerating the slide isn't the spring's function.

Actually, even if the deceleration effect is relatively weak, it could still be pretty important. An unimpeded impact between two mostly unyielding objects results in a pretty impressive amount of force applied because the distance involved in stopping the motion is very short. Since force is proportional to energy divided by deceleration distance, with a very small deceleration distance, the force becomes very large.

If one can spread out that deceleration distance, even a tiny bit, it can dramatically reduce the amount of impact force generated by the collision. So, for example, if one could increase the distance required to decelerate the slide to zero from 0.01" to 0.02", that would halve the amount of energy applied by the impact. In other words, even if the heavier spring really only does a tiny bit of effective deceleration near the very end of the slide's travel, it could still result in a very large decrease in the amount of force applied by the slide impact.

Just for absolute clarity, I'm not necessarily arguing that springs ARE intended to decelerate the slides although it seems reasonable to me that it could be at least part of the reason for a recoil spring. I just don't believe the arguments and reasoning provided so far are good support for the assertion that they aren't.

Promise me that you'll read this last post, John. It's a little involved, but it's factual.

Frame damage from slide impact is a myth thrust on us by people who have a dog in the fight... those who make money selling springs and shock buffers.

In the early to late 60s, my father and uncle hit the shows and bought up old USGI pistols for a song... then bought the parts... and rebuilt the guns for beater duty, and we beat'em hard. Surplus GI hardball was embarassingly cheap, and they bought it in scary quantities. A few of the nicer ones were resold to finance their operation. I learned the trade at their knees.

I've had my hands in literally hundreds of GI pistols over the last 46+ years. Many of them were badly worn and had seen a lot of use. In those days, there were no shock buffers and there was only one spring available, and it wasn't 16 pounds, either. I've never seen impact damage to the slide or frame abutments in any of them. In spite of much evidence to the contrary and detailed explanations from knowledgeable, experienced people... all it took was a banner ad in a gunzine to send Chicken Little on a mission. "ZOMG! If you don't have a heavy-duty spring and a shock buff in your gun, you're destroying your gun! Better run git some quick or your gun is dooooomed!"

*cough*

I first heard of this terrible frame damage about the same time that I saw the first shock buffers for sale in gun shops... and coincidentally... about the same time that parts catalogs started advertising heavy-duty recoil springs. (Better git some!)

Still being in possession of several very old, very used GI pistols... I broke'em down and looked closely. I didn't see any damage.

Keep in mind that in those days, the frames and slides were dead soft, and didn't average more than 26-28 Rc. Slides were spot-hardened starting in 1941, and not in the impact abutment. In 1936, Colt started using a hardened steel insert in the breechface to eliminate deformation from recoil pounding. These can be seen and are often mistaken for marks left by the end mill used to cut the breechface.

So... on occasion... I'll bring it up whenever I hear about this destructive peening. First, I explain it with mechanics and physics. The cry goes up. "ZOMG! Frame battering!"

Sometimes, I take'em to the range with a high-mileage pistol and a few hundred rounds, and use a very light spring. I've gone as low as 10 pounds. Still it comes. "ZOMG! Frame damage!"

Then, I remove the spring completely, and continue firing the gun, and still I hear the same tired warning "ZOMG! Total frame destruction!" in spite of the fact that there is none. They don't even believe their own eyes. Once, I was even accused of having a specially tricked-out pistol that stopped the slide before it hit the frame. (As if.)

They've bought the snake oil... so I rarely bring it up any more. This time, I was bored. I should have just gone out and played with the dogs.

I've read all the posts so far and I generally take the time to read the posts you make because I value the experiential information you provide.

Ok, here is what seems to me to be a reasonable analysis assuming that the information you have collected and provided here tells the complete story as far as 1911 steel framed pistols are concerned.

1. A standard 1911 is set up (either intentionally or through happy coincidence) so that the slide velocity creates impact force that is generally below the endurance fatigue limit of the slide and frame, even without any deceleration benefit that the spring provides.

2. Given that the impact energy from a Commander slide is only about 10% greater than a standard 1911, it's probably reasonable to begin with the starting assumption that (at least with steel frame guns) it will also not impart an impact force that is above the endurance fatigue limit of the slide/frame. With aluminum frames, it would be an entirely different story given the completely different endurance fatigue properties of aluminum and steel.

The first point seems pretty solid based on your experience, although frame failures aren't totally unheard of. The second point is based on an assumption and isn't quite as solid.

It should be noted that both points apply pretty much exclusively to steel- framed 1911 pistols and variants that follow the original design fairly closely.

Do a 'Bill Drill' as fast as you can.
'If it strings down', lighten the recoil spring.
'If it strings up', increase the recoil spring weight.

What changed other than slide acceleration?

It's not energy that does the damage. It's momentum. Momentum is the quality of a moving object that causes it to keep moving when it meets resistance... drives it forward and through... deforms the object that it hits. Momentum is what makes the bullet penetrate... not energy.

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Do a 'Bill Drill' as fast as you can.

This is a neat trick that works, but it's not the function of the spring.

I'm trying to make three points.

One is that the spring's function is to return the slide. It has no other. It's an action spring. A bolt return spring.

The second is that frame impact damage isn't nearly the concern that we've been led to believe. Dog in the fight. The slide doesn't hit the frame that hard anyway. Go shoot one a few times without a spring and see.

The third one is that the faster lower mass slides don't carry the potential for damage that the slower, higher mass slides do. The low-mass slides require a stronger spring for a reliable return to battery... not keep the frame from destruction. The frames are a bit tougher than that. If +/- 2-4 pounds of spring determined whether a 1911 frame lived or died, the gunsmith junk parts barrels would be stacked high with frames.

Consider 1SOW's post. Some competition shooters are using springs as light as 8 or 9 pounds with major power factor ammo. Some of those frames endure a half-million rounds. Quote:
Frames do fail.

Never said they didn't. Anything will fail eventually, given enough use. I've seen frames crack at the junction of the spring tunnel and the front of the rails... but that's the nature of thin cross-sections and sharp corners. Those cracks are self-limiting, and don't compromise the function of the gun. My "Brace of Beaters" frames cracked several years and many tens of thousands of rounds ago. The cracks haven't traveled and the guns work fine.

Basically just tryin' to shoot holes in a few popular myths.

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It's not energy that does the damage.

This is a logically and scientifically bankrupt statement. Energy and momentum are both real, actual, measurable, calculable, well-defined, well- characterized, totally accepted by the scientific community, physical properties of moving objects. Both relate, in one way or another to any damage done by a moving object because it is not possible for a real world moving object to have momentum without energy or energy without momentum.

Depending on the variables available in the particular situation, it may be easier to determine the amount of damage using momentum or using energy in the calculation, but the idea that it's possible to separate one from the other and say that one causes damage while the other doesn't is simply unsupportable from any logical or scientific standpoint.

Momentum and energy are two different sides of the same coin, it's just sometimes easier to approach a particular problem from one side vs. the other. If you try to discount or downplay or ignore one or overemphasize or exaggerate the other, it will not be possible to achieve an accurate understanding of the basics of the science of moving objects.

When talking about damage, it's often easier to look at the problem from the energy side since energy is more simply related to the potential of a moving object to cause damage than momentum. In this particular case, the key factor in understanding the scenario was the impact force which could be quite easily compared using energy and with the assumption that both slides were decelerated to zero over the same distance.

It could have been done with momentum but then one would have to know the amount of time it took to decelerate both slides to zero and that's trickier to determine.

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Momentum is the quality of a moving object that causes it to keep moving when it meets resistance...

Momentum is the quality of a moving object that causes it to "try" to keep moving when it meets resistance. Whether it actually does keep moving or not depends on how much resistance it meets, it's not simply a matter of looking at the momentum.

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(momentum) drives it forward and through... deforms the object that it hits.

This is not true. Whether there is deformation or not has to do not just with the properties of the moving object (mass, velocity, momentum and energy) but also involves the properties of the materials involved.

Assuming one knows everything about the impact, one could calculate the force applied by the impact using either momentum OR energy, because momentum and energy are calculated from the same two variables. With the force, one could look at the material properties involved and make a determination of what sort of deformation might be expected.

If you look at peening or deformation comparisons for metals, they typically use the force applied as the independent variable, they don't use momentum OR energy. Looking at this from an energy standpoint just made it simpler to get a quick feel for the different levels of force applied.

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Momentum is what makes the bullet penetrate... not energy.

It's true that momentum is more closely related to penetration than energy is, but it doesn't "make the bullet penetrate" unless the integrity of the projectile is sufficient and the material properties of the target medium are overcome by the momentum. In other words, it's just one piece of the picture. The simplest part, truth be told.

Again, there is absolutely no way for a moving object to have momentum and not also have energy. The two things can not be separated, they're just two ways to look at the same problem. The fact that momentum can generally be more closely related to bullet penetration than energy does not exclude energy as a quantity that is related to the damage or the penetration caused by the projectile.

Both properties are useful in understanding the resulting damage. The reason I focused on energy was because it made the calculations/visualization easier in the problem that you set up for analysis.

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The third one is that the faster lower mass slides don't carry the potential for damage that the slower, higher mass slides do.

Even by your own analysis, this doesn't follow. If they have the same momentum (as you claim) and momentum is what causes damage (as you claim) then clearly the "the faster lower mass slides carry the same potential for damage that the slower, higher mass slides do". In other words, your statement directly contradicts your analysis from the first post of this thread.

I guess that's neither here nor there. Based on the rough calculations I did, for this particular comparison, the faster, lower mass slides DO carry more (not a lot more, only about 10% more) POTENTIAL for damage than the slower, higher mass slides do. Whether or not that potential is realized and damage is actually increased has to primarily to do with the material properties of the steel used in the frames (particularly the endurance fatigue limit) and the efficacy of any measures the designer takes to reduce the increased force applied by the higher energy impact.

http://www.thehighroad.org/showthread.php?t=57241

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This is a logically and scientifically bankrupt statement. Momentum and energy are two sides of the same coin

John... I never said that energy meant nothing. Everything means something. Certainly energy is involved, but... like the 5.56/.45-70 analogy... it's momentum that causes the bulk of the damage because momentum is what keeps the slide driving on...compressing the abutment and pushing it backward. Rearward deformation... peening... is the cry.

Everybody seems to feel like it's energy alone... that energy is the main concern... because that's all that's referenced when the talk turns to light, fast slides and the springs that are needed to dissipate the energy. The main point that I try to get across whenever this comes up is that the Commander/Officer's Model slide doesn't carry any more hurt than the 5-inch slide... and probably less.

I think that if somebody calculates the velocities in both sans springs, and does the math... this will be borne out. There's not enough difference to make it an issue.

Go calculate the energy difference between a 200-grain bullet at 900 fps, and a 230 at 830. I did. There's only about 7-8 foot pounds between the two with approximately 9% less bullet mass and approximately 9% more velocity. That energy spread can easily be seen with the same ammunition from one shot to the next.

And... as I've pointed to in this thread... whatever increase in energy there is is not only small, it's offset by the decreased momentum... and vice-versa.

The concern over frame battering is largely unfounded. I'm satisfied with that statement. The added concern over Commanders and Officer's Models due to their higher velocities and higher energies is... well... a Chicken Little response. It's just not there. I've long realized that, even before I thought it through carefully and tried to put it into words. At first, I thought... Yeah. That makes sense...but then after some consideration... I thought... No. That doesn't make sense. There's not enough difference to mean anything.

Anyway...

Technical arguments over spring function and other sideways topics, I guess I should simplify my message with this thread... the point of which seems to have escaped a few.

The concerns over frame destruction are unfounded. You don't need heavy springs and shock buffers. Unless you plan to burn through 50,000 rounds a year every year, you don't need to worry... not even with +P ammunition... not even in a Commander or Officer's model... not even with identical spring rates. If you do plan to shoot one that much, eventual destruction is an understood and accepted part of it. Everything will fail, given enough use.

Simple enough?

Back when I wrote that old thread up, I'd been raising the cry for a while over the frame battering concerns... and in the process, I drew more flak than a B-17 over Berlin in 1944. So, I decided to give'em a formula that supported their beliefs...and still I took incoming from several emplacements. Some days, an old mechanic just can't win.

So, I started working them toward using a smaller radius on the firing pin stop and a full power mainspring to control slide acceleration and impact... and the aerial bursts just kept comin'. It struck a chord in a few... it struck a nerve in a few... and still others wouldn't have believed it if John Browning himself had appeared and explained it.

Tryin'... tryin'... tryin'... to get it across that the concerns over frame destruction are imaginary. My message is "Go shoot it. Don't worry. It won't fall apart with the stock spring and 200 rounds of +P. The old girl is way yonder tougher than that."

I think the recoil discussions are interesting.

My father sold the hydraulic recoil math to Rock Island Arsenal and the hardware built with it to Detroit Arsenal.

Now, 50 years later, he is suggesting I build a handgun recoil assembly with it.

Interesting. Wonder how much complexity and cost it would add to the gun. Some things work very well, but it can reach a point of diminishing returns... especially when the spring system works so well. Cheap. Easy to maintain. Dead simple.

Didn't someone sell some sort of hydraulic full length guide rod setup for 1911's back in the 80's? Seems I remember vague talk of such a thing.

Almost forgot.

If we assign a 5-inch slide a weight of 14 ounces, and the Commander at 10% less... 12.6 ounces... and a slide speed at impact of 20 fps for the former and 22 fps for the latter... a straight 10% increase in velocity, which is gonna be pretty close with standard hardball according to the Venezuelan Rocket Scientist, Tiro Filo on the 1911 forum...

The Commander slide strikes with an additional 7 fpe, assuming no recoil spring and equal ammunition.

Seven.

If we then assign an equal spring rate for both, and owing to more rapid deceleration with less mass... it might make... I dunno... six.

Six foot pounds more energy. Six.

Hardly even worth mentioning, no?

Quote:
...it's momentum that causes the bulk of the damage because momentum is what keeps the slide driving on... compressing the abutment and pushing it backward.

Yeah, it's just not possible to separate things that cleanly. If you really want to look at it from the way most materials are actually tested for deformation then the way to do it is to look at the force applied. I used energy to calculate that force because it was simple to do so. If you can get high-speed footage for both slides and measure the time differences then you can do it with momentum instead, if you prefer.

Force = kinetic energy / distance
Force = momentum / time

Same Force either way. Quote:
Six foot pounds more energy. Six.

It doesn't look like much if you look at the energy, that's why you have to look at the force applied. Force applied (in the case without a spring) is related to the energy of the moving object divided by the distance it takes to stop the moving object. Since the slide basically hits the frame and is stopped in a tiny fraction of an inch, the relatively small energy figure is divided by a really tiny distance which results in a fairly large force.

It's true that the increase in the force would only be about 10% based on the figures I've managed to scrounge up, but given a fairly large force to begin with, an increase of 10% could conceivably be significant.

I'm not going to bump the old thread, but I'll respond to one aspect of it here.

 
Quote:
 The momentum of the bullet equals the momentum of the slide and barrel.
 [1100][.026]=V[.5+.1}
 V=47.7 feet per sec
 Velocity of slide and barrel = velocity of slide
 Energy of slide = .5mVV= one half mass velocity squared
 Es=.5[mass of .5 pounds][47.7][47.7]
 Mass = [wieght]/gravity= .5/32.2=.0155
 Es=.5[.0155][47.7][47.7]=17.64 foot pounds of energy
 
 The energy required to pull back the slide = [force][ distance]
 Force = average force = [15+42]/2 = 28.5 pounds force
 distance = 1.656"=1.656/12=.138 feet of slide stroke
 Eslide = [28.5][.138]=3.93 foot pounds
 
 BUT WAIT A MINUTE! 17.64 DOES NOT EQUAL 3.93!
 
 Not all of the bullet momentum went into the slide and barrel.
 Some of it accelerated the hand.
 Only 3.933/17.64= 22% went into the slide and barrel. 

First of all, pulling the slide back doesn't necessarily reflect the amount of force required to reliably extract and eject a fired cartridge case.

Second, it tells us that even if we neglect that fact, the slide probably hits the frame with more energy than it really needs to.

Finally, it's not really accurate to say that "not all of the bullet momentum went into the slide and barrel". It would be accurate to say that the force required to retract the slide is less than the force applied to the slide by the recoil momentum.

The fact is that all of the recoil momentum DID go into the slide and barrel.

Some of it was transferred to the frame via impact and then to the shooter when the barrel was unlocked and stopped by the frame. Then some of the slide momentum was expended extracting and ejecting the fired case and compressing the recoil spring. Whatever slide momentum was left over after the fired case was extracted and ejected, the recoil spring was compressed and the slide was fully retracted was then transferred to the frame via impact and finally to the shooter.

It's all academic, John. This wasn't about equations showing exact energy and momentum to prove which one *actually* hits harder. The whole point was... and is... that there's not enough difference between the two pistols for the short one to "need" a heavier recoil spring to control impact. One has more energy. One has more momentum. Flip a coin to decide the winner.

It's a lot like an argument on which bullet is more lethal when the contestants are 150 grains at 1250 fps and 145 at 1300... of course assuming that all else is equal. Whatever the difference is... is of no consequence.

The frame isn't teetering on the knife edge of destruction. Another 2 pounds of spring behind a lighter, faster slide won't mean the difference between a long, trouble-free service life and a short trip to the scrap barrel. I've been proving that for years.

So, the root question still looms. The one that I asked in the first post. The whole theme of the thread.

If it's not about impact... and it's not... why are there heavier springs in the short variants?

By the way, the direction this thread has taken was predictable. Any time that I bring these points up in a discussion on springs, the responses are almost invariably: "ZOMG! Frame destruction!"

Lotta kool-aid out there, and with so many who like kool-aid...

Quote:
Finally, it's not really accurate to say that "not all of the bullet momentum went into the slide and barrel". It would be accurate to say that the force required to retract the slide is less than the force applied to the slide by the recoil momentum.

I wrote that 10 years ago... but I still think I figured it out and explained it ok.

The idea was that 80% of the energy went missing and to explain where it went... into hand movement, and not into the recoil spring.

In the book "How the Mind Works" they measure that people can understand more complicated problems when they suspect they are being cheated. That is why I often put math problems in those terms.

I don't have a variety of springs or 1911s to do this with, so if someone wants to help me out, it would be appreciated.

Measure the force it takes to hold the slide back slightly when the slide is nearly closed (f1), and when it is nearly open (f2).

Average them, and multiply by the distance the slide moves (2.5"?)to get the energy the spring is absorbing from the system.

E=distance*(f1+f2)/2

I think you'll find its pretty neglible.

It is, owen. The difference in impact energy or momentum or purple pixie dust between the 5-inch gun and the 4.25-inch gun is so small that it doesn't even rate consideration... even without a recoil spring. By the time all the other delaying/retarding forces get done with the system, the slide just isn't moving very fast at the instant of impact.

Which brings us back to the original question:

The recoil/action/return spring. What is it for? What it its function?

"why are there heavier springs in the short variants?"

Because the buyer expects it?

IMHO The recoil spring function is to return the slide to battery.

The standard spring is about 2.5 pounds per inch, the 16 pound rating is measured when the spring is fully compressed.

If we assume a 2 inch stroke for a fullsize, 5 inch 1911 the force will only be 5 pounds available to return the slide to battery.

On a shorter slide the stroke if I assume a one inch stroke the same spring rate will only provide 2.5 pounds.

The 20 pound spring may have a 5 pounds per inch rate, which for the one inch assumed stroke will provide the same amount of force to retun to battery as the fullsize gun.

The higher spring rate will provide the same amount of force on a shorter stroke, that is why the spring rate is higher.

This is a very simplistic approach as there are other issues such as the weight of the slide and friction.

Tuner I agree with you 100 %

CMC... You've got it!

Quote:
The frame isn't teetering on the knife edge of destruction. Another 2 pounds of spring behind a lighter, faster slide won't mean the difference between a long, trouble-free service life and a short trip to the scrap barrel. I've been proving that for years.

Even if we take this as absolute truth in the context of your testing and experience, if we want to eliminate the possibility of over-generalization, I think we would have to limit the scope of the assertion to 1911s & variants-- maybe even to only steel-framed 1911s & variants.

Quote:
By the way, the direction this thread has taken was predictable. Any time that I bring these points up in a discussion on springs, the responses are almost invariably: "ZOMG! Frame destruction!"

I don't believe any of my responses would qualify as "ZOMG! Frame destruction!". In fact, I tried to explain the gist of my responses earlier to avoid misinterpretation.

Here it is again:

"Just for absolute clarity, I'm not necessarily arguing that springs ARE intended to decelerate the slides although it seems reasonable to me that it could be at least part of the reason for a recoil spring. I just don't believe the arguments and reasoning provided so far are good support for the assertion that they aren't."

Quote:
The idea was that 80% of the energy went missing and to explain where it went... into hand movement, and not into the recoil spring.

Ok, it's true that there's more energy applied to the slide than is required to compress the recoil spring. Which is good, because that's not all it needs to do. It also has to extract the fired case and eject it with sufficient force to insure that it clears the ejection port cleanly.

And even after it does that, there's still momentum left over that drives the slide to impact the frame and thus transfer its remaining momentum to the frame and then to the shooter (hand movement).

Quote:
...people can understand more complicated problems when they suspect they are being cheated.

Interesting and probably true. However, I think that after you draw people in and get their interest, at some point you have to follow up with a complete explanation so that people aren't left with an inaccurate view of the problem.

Saying that not all of the momentum goes into the slide and barrel is certainly intriguing but it's also inaccurate. Saying that not all the momentum that goes into the slide and barrel is used to compress the recoil spring or saying that the momentum required to compress the recoil spring is less than what is transferred to the slide and barrel gets the point across with a lot less potential for leaving people without the full picture.

Quote:
IMHO The recoil spring function is to return the slide to battery.

Your analysis is good, I like it. But again, I think that the conclusion is overarching. While you've provided an excellent explanation of one purpose of the recoil spring, that explanation doesn't eliminate the possibility that the recoil spring performs other useful functions as well.

John, I never said that we can't do other useful things with recoil springs... assuming that you're talking about selecting one that brings the gun back on target for faster split times and the like. I've even alluded to that, but it's not what the spring is there for. It's what we've decided to use it for, and it's a fairly recent practice.

You can go buy a new Mustang on Saturday and take it to the dragstrip on Sunday, and maybe even with a trophy with it... but that isn't proof that Mustangs are designed for drag racing.

In M14 rifles, the action spring's purpose is clearly understood. It returns the bolt.

The slide on an autopistol is no more than a bolt. It performs exactly the same function as the bolt in a self-loading rifle. The spring that powers it does exactly the same thing that it does to the rifle bolt and in exactly the same way. It gets compressed by the bolt... and when it stops... it pushes the bolt forward. In both weapons, that's what the spring is put there to do, and that's pretty much all.

To what extent does the recoil spring determine the ejection pattern? I have been told by both Jerry Keefer and Bob Marvel (during 1911 class at MCC) that you can change and adjust where the empty cases end up by using different recoil springs.

I shoot Bullseye with a slide mounted Ultra Dot. The pistol has a firing pin stop with just a slight radius at the bottom. In an earlier post you said that the recoil is very soft if the pistol has no spring at all. So to absolutely minimize recoil, I should go to the lightest recoil spring that feeds reliably?

Yep, Tom. You can juggle springs and change the ejection pattern. That's not a new thing. The change comes from the speed of the case when it hits the ejector.

That's not the spring's function, though. It's just one thing that can be manipulated by different spring rates. It's important to some... not so much to others. Personally, as long as the case clears the port and doesn't hit me on the noggin, I don't care where it lands.

I took my Dan Wesson Razorback to the range today, after having done the squared firing pin stop and heavy mainspring mod to it, same as my Delta Elite.

I find that I need to change recoil springs depending on what I shoot. I had an 18 pound spring in and was shooting Georgia Arms Canned Heat ammo, worked beautifully, put all the brass literally right together in a nice pile about 4 feet away.

Switched to my SWC barely Major reloads and was crushing some brass, had to drop to 16 pound recoil spring. I was surprised that small amount of spring change would make such a difference. I'm still learning from all this.

Quote:
The slide on an autopistol is no more than a bolt. It performs exactly the same function as the bolt in a self-loading rifle. The spring that powers it does exactly the same thing that it does to the rifle bolt and in exactly the same way. It gets compressed by the bolt... and when it stops... it pushes the bolt forward. In both weapons, that's what the spring is put there to do, and that's pretty much all.

Just to make sure we're on the same page...

You're asserting that when a manufacturer recommends that the recoil spring on a particular pistol needs to be changed very frequently (for example, some of the new crop of tiny pistols in service pistol calibers apparently need springs every 1K rounds or so if you believe the manufacturers), they're saying that if you don't change the springs that frequently, your gun will begin to have feeding problems as the spring gradually gets too weak to properly return the slide to battery.

You're further asserting that they are not saying that using the recoil springs too long will be deleterious to the major components of the pistols as the increased impact forces due to the decreased deceleration effects of the weakened spring batter the slide and frame.

No, What they are saying is that they didn't have a large enough envelope for an adequately deisgned spring, so they sacrificed part life, by overstressing the spring they could actually get to fit.

I said that the spring's function is to return the slide, and that whatever else it does is incidental... and that if the user decides to juggle spring rates to achieve a desired effect on the gun's handling characteristics, he is using the spring for something besides what its purpose is. It can be done. It doesn't prove that's what it was designed to do.

I said that the notion that a heavier spring is needed in shorter/lighter/faster slides to prevent frame destruction is unfounded because:

The slide doesn't hit the frame all that hard to start with... even without a spring, and:

There isn't enough difference in the guns' frame impact to make it necessary, and:

I said that the heavier springs are put there to give the less massive slides enough velocity to create the momentum that is required for a reliable return to battery.

As an aside, I've let the springs in mine go far beyond the recommended change schedule in order to prove that the frame won't be damaged. Far beyond. I've run very light springs for thousands of rounds. My frames' abutments are just fine. Other than having no bluing on them, they look like new.

I believe that Jim K ran a Norinco for about 8,000 rounds with the OEM spring without issues. Ask him.

This "Frame Destruction" business is fostered by people who have a dog in the fight. They sell springs. They really want you to buy a dozen.

Now, if you want to believe that you're saving your frames with heavy-duty springs and shock buffs, or by changing springs every 2,000 rounds... or every 200 rounds if you want to... it ain't a thing to me. Believe it if you want. The evidence just doesn't support it.

...or, maybe I'll just fit a small radius FPS to my new Bear UTC since it's the only one of my 1911's that doesn't have one (except the Detonics) and just keep on loving 1911s and shooting them.

As for the conventional wisdom, I've gone in the opposite direction for years. Instead of the heaviest spring that allows the slide to lock, or judging it by how far from the gun the brass lands... I use the lightest spring that still puts the slide in battery up to 500 rounds with a dirty gun... and my ammo is pretty funky. Home case bullets with soft lube and Unique. For my beaters, that means 16 pounds. On my spankin' clean carry guns... 14 pounds is just fine and 16 for the Commanders.

So, it boils down to feed/return to battery reliability, especially as the gun starts to get dirty. That's when too little spring will tell the tale.

Feeding is more a matter of feed and barrel ramp geometry and extractor tension and deflection.

If you're concerned with slide speed/impact, there are better ways to accomplish that without the problems associated with over springing the slide, starting with the mainspring.

I thought I was reading it from what you were saying. You seemed to be saying that recoil springs were only bolt/slide return springs and that would mean that their primary function is providing enough return force to insure proper feeding. Quote:
Shorter, less massive slides do require stronger springs to accelerate them to velocities that are high enough to provide the necessary momentum for feeding...

It appears, in fact, that IS what you're saying.

Quote:
So, it boils down to feed/return to battery reliability, especially as the gun starts to get dirty. That's when too little spring will tell the tale.

It further appears that you're saying the symptom of too weak a spring is feeding problems, particularly with a dirty gun.

So, if we accept all this as fact, then when a manufacturer recommends frequent spring replacement, it follows that what they're concerned with a weakened/worn spring no longer providing enough return force to insure proper feeding. i.e. They want you to change it frequently so it keeps performing its bolt/slide return function properly.

Isn't that pretty much exactly what I said in my last post?

Which gets me to my next question. I'm thinking of one particular manufacturer, that after having a particular product on the market for many years, suddenly started informally (or at least quietly) recommending much more frequent spring replacement. However, and here's the problem. They were not addressing complaints about feed reliability with this recommendation, they were addressing component failures and durability issues. It seems to have been an effective tactic, effective enough that the company recently released a new crop of pistols using an entirely different spring design to address the issue.

The question is this. Are we really sure enough about this general theory that we can come straight out and say that this manufacturer simply doesn't understand how their own guns work?

That's exactly what I'm saying. If there is any consideration given to frame impact and damage by the engineers... which I strongly doubt... it's a very minor consideration.

Quote:
Isn't that pretty much exactly what I said in my last post?

Maybe it's me... and maybe I didn't take enough time to read it due to haste and time constraints... but it seems like all I've gleaned from the arguments is that spring change and/or heavy springs and shock buffs are necessary to prevent frame damage... which just doesn't happen in normal use. It doesn't happen with pretty heavy use, either. If so, I apologize.

Or maybe it's because I expect it to the extent that I half read these claims and skip to the evidence. If so... I apologize again.

It's gotten so ridiculous that I've even seen the insistance to switch springs according to the ammunition. Understandable to go light if the ammo is of the powderpuff variety... but dire warnings of frame damage and to switch to heavier springs for +P...in a carry gun... is just a bit absurd. If the gun won't stand 7-8 rounds of +P with the stock spring, it's subject to come unwrapped with any reasonable spring.

Or, maybe I've been trying to get these points across for so long that I've gotten a little impatient and hair-triggered in my old age.

At any rate, it falls into the same category as:

"OMG! They're letting them carry concealed weapons! There's gonna be blood in the streets like Dodge City and Tombstone!"

And it just hasn't happened. They still keep screamin' about it, though.

They are built on very similar 1911 specs and were the first of the imported, compact and light weight (alloy framed) .45's.

Now I'm wondering what can be done to tame them? Hmmmmm.