Recoil Spring Study

[JohnKSa]

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.

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.

 

[1911Tuner]

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.

 

[JohnKSa]

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.

 

[1SOW]

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?

 

[1911Tuner]

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.

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?

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.

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.

 

[JohnKSa]

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.

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.

(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.

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.

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.

 

[Clark]

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

 

[1911Tuner]

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.

 

[1911Tuner]

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?

 

[1911Tuner]

Clark...

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.

The other morning, it was rainy and cold, and I couldn't get out and
work with the Huskies. I'd cooked up another pot of turbocoffee, and kicked the gas logs on to ramp up the warm fuzzies in here. I was bored, and had been in a persnickety mood for a day or two...so I thought: "What the hell. Let's go rattle a few cages and see who growls."

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."

 

[Clark]

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.

 

[1911Tuner]

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.

 

[TexasRifleman]

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.

 

[1911Tuner]

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?

 

[JohnKSa]

...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.

Six foot pounds more energy. Six.

Hardly even worth mentioning, no?

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.

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.

There are a couple of things that this tells us.

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.

 

[1911Tuner]

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...

 

[Clark]

JohnKSa
Member


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.

 

[Owen]

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.

 

[1911Tuner]

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?

 

[JohnBT]

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

Because the buyer expects it?

 

[CMC]

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 %

 

[1911Tuner]

CMC...You've got it!

 

[JohnKSa]

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.

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."

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).

...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.

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.

 

[1911Tuner]

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.

 

[Tom-C]

1911 Tuner
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?

Thanks