Strength of slide return spring in a 1911

mikemyers · Sep 9, 2015

1911Tuner said:
......Equal momentum is only possible in the absence of outside force, or in the presence of equal outside force. Thus, it's theoretical in a real gun firing real ammunition.......

There's another way to look at this. Suppose, somehow, by magic, you could transform yourself into the slide on the gun, as it was being fired. From your point of view, you'd see the force of the bullet pushing it one way, and you'd also see the force of the gun's frame pushing it the other way. You'd also see other, smaller, forces pushing it the same way as the frame.

You would only notice the force from the bullet as the bullet and the explosion within the gun during the time the bullet hadn't exited the gun, and you'd only notice the forces from the frame friction, air pressure, etc., while trying to move away from the bullet.

..........or, put another way, if you had a 300 pound football player try to push you backwards, at the same time as another 300 pound football player pushed you forward just as strongly, you might be squished, but you wouldn't find yourself accelerating towards or away from either of them.

mikemyers · Sep 9, 2015

MEHavey said:
.......The gun was tested over several magazine's worth of each of the loads shown, and the springs replaced (going sequentially lower) until the slide would fully function/pick up the next round, and correctly lock back on the empty magazine each and every time.......

I'm not sure if I fully understand your chart. I assume you mean the spring value is the maximum strength of spring that could be used in that gun, with that ammunition, that would still allow THAT gun to perform properly.

I don't disagree that the gun you tested behaved the way you recorded it, but my first thought is that you would need to try this test on a lot more guns. Les Baer says to leave the 18# spring in his Premiere II until/unless one is firing extremely light loads - when the gun stops functioning, then you need to get a softer spring.

When I did all my shooting, there were no problems whatever. Les wants me to keep the 18# spring in the gun even when I go to the 185gr bullets (unless I find the gun doesn't cycle correctly, of course).

Based on everything I've read in this thread so far, much of which now makes sense to me, I think you need to re-do your test, trying many more guns, and even then, you need several guns for each model you test. The guns may have the same name stamped on the side, but as 1911tuner described earlier, each gun is unique...... as in how far the ejected shells get thrown.

45_auto · Sep 9, 2015

From 1911tuner post #99, all within a couple of sentences:

1911tuner said:
Recoil isn't momentum at all, but I've said that all along.

I know, which is why it's a waste of time trying to communicate with you (I applaud JohnKSa for even trying!). You refuse to learn. Your understanding of the physics of 1911 operation is the equivalent of someone noticing that there are more umbrellas present when it rains and concluding that umbrellas cause rain.

Perhaps you could correct the Wikipedia article on "Recoil". It would appear that they (and Isaac Newton) have a fundamental disagreement with your views:

https://en.wikipedia.org/wiki/Recoil

Recoil (often called knockback, kickback or simply kick) is the backward momentum of a gun when it is discharged.

Another simple explanation on gun recoil if anyone cares to research it further here on the "Physics of Everyday Stuff":

http://www.bsharp.org/physics/recoil

Gun recoil is a result of momentum conservation, which is an extremely important fundamental principle. Newton was talking about momentum conservation when he wrote "every action has an equal and opposite reaction".

...the backward recoil gun momentum balances the forward bullet momentum to maintain zero total momentum.

1911tuner said:
Recoil is acceleration....What we recognize as recoil is momentum

Not much use even trying to reconcile those two statements. You don't understand the fundamental differences between force, acceleration, momentum, and impulse.

1911tuner said:
Equal momentum is only possible in the absence of outside force, or in the presence of equal outside force. Thus, it's theoretical in a real gun firing real ammunition.

Sorry, it's real. Been commonly known for hundreds of years and it's used by engineers designing recoil systems every day.

You should be ashamed of the false information you spread to the readers of this thread

1911Tuner · Sep 9, 2015

The gun was tested over several magazine's worth of each of the loads shown, and the springs replaced (going sequentially lower) until the slide would fully function/pick up the next round, and correctly lock back on the empty magazine each and every time.

There are a few problems with that approach...not the least of which is variations in ammunition from lot to lot or even within the same lot. This still comes back to attempting to minimize slide to frame impact, and...as I've shown...the slide just doesn't hit the frame hard enough to be a concern.

The main problem is that the slide doesn't have any dwell time at the rear to give the magazine time to get the upcoming round into feeding position and stabilized.

And then, there's the felt recoil to be considered. The stiffer the spring, the sharper the recoil because the spring becomes a force vector between the slide and the frame in an action-reaction system separate from the one that comes from firing the cartridge. Because force forward is force backward, the stronger the spring, the harder and faster it pushes backward on the frame.

And we're back to the first point that the chart is way too complicated. There's little or nothing to gain in trying to use spring rates to "tune" the gun to 50 fps increments. It's not necessary.

Because the spring's function...its reason for being there...is to return the slide to battery, and whatever else it does is incidental.

mikemyers · Sep 9, 2015

JohnKSa said:
......When you hold the slide closed, the slide doesn't reciprocate with respect to the frame, but it does move in recoil with the gun and the shooter's hand. The momentum initially goes into the slide and barrel since they are locked together. They will, as a result, initially have the same velocity until something impedes one or the other.This is a statement that demonstrates a fundamental lack of understanding of the science behind this topic.......

In the video I linked to, it shows that the slide doesn't move when you hold it back with a finger. Technically, I should have written that the slide doesn't move, relative to the frame. You're right, I could have added that the slide and frame are moving backwards, and for that matter they're moving through space along with the rest of the planet.

........I don't disagree with the idea that the energy of the bullet going one way has to be matched by the energy of the gun trying to move back the other way, but just as the frame of the gun can "absorb" the energy from the slide, the shooter can "absorb" the energy from the frame, and presumably the planet Earth could absorb the energy from the shooter, if he was a Ransom rest, and not a human.

(If you had a 200 ton block of steel, with a barrel welded to the front of it, and were able to fire a bullet from that barrel, nothing would seem to move, other than the bullet, and perhaps this would just have a minuscule effect on the movement of planet Earth.)

MEHavey · Sep 9, 2015

Les Baer says to leave the 18# spring in his Premiere II until/unless one is firing
extremely light loads - when the gun stops functioning, then you need to get a softer spring.

And I agree w/ Les Baer... and if one looks back is what I've recommend all along: Test then adjust as req'd
What the chart showed is that that gun would not properly function (i.e., would FTF, stovepipe, not lock back)
unless/until the spring value was reduced to the poundage shown.

The trend of the chart was clear: Lower energy loads required lower spring constants. I would not argue that
other guns/loads might displace the line on shown the chart higher/lower as circumstances might demand.
But I would also expect the slope on that displaced line to remain... higher energy loads would yield higher
spring constants (and vice versa)

If the gun functions -- shoot it.
If it doesn't, adjust.

45_auto · Sep 9, 2015

mikemyers said:
I don't disagree with the idea that the energy of the bullet going one way has to be matched by the energy of the gun trying to move back the other way

If you don't disagree then you're incorrect also, and apparently do not understand the difference between energy and momentum.

A 2.5 pound 1911 firing a 230 grain bullet at 850 FPS has a recoil (kinetic) energy of about 6 ft-lb. The bullet has about 370 ft-lb of kinetic energy.

This site has an online calculator:

http://www.handloads.com/calc/recoil.asp

Jim Watson · Sep 9, 2015

I don't disagree with the idea that the momentum of the bullet going one way has to be matched by the momentum of the gun trying to move back the other way, but just as the frame of the gun can "absorb" the momentum from the slide, the shooter can "absorb" the momentum from the frame, and presumably the planet Earth could absorb the momentum from the shooter.

Fixed that for you.
Momentum is a vector quantity. You start holding the gun still, momentum zero, and fire a shot. The momentum of the bullet going north is equal to the momentum of the gun going south; net momentum still zero. An automatic with separately moving slide and barrel complicates the fine calculations but the total momentum does not change, even when recoil transmits it to the shooter's body and thence into the planet. Same deal on the other end, the bullet's momentum is delivered to the target and as the target quits moving, to the planet. Momentum change of the Earth, zero.

Energy is, of course, conserved, but it is not a vector quantity; the gunpowder is producing a given amount of energy and it doesn't care which direction it is exerted. The recoil energy of the gun is a small fraction of the muzzle energy of the bullet because of the squared velocity term.

Many years ago, as the British game gun was being perfected, there was a lot of attention paid to recoil. One does not want to be afflicted with "gun headache" when shooting driven pheasants all morning. The gunmakers and instructors at the Holland's shooting school concluded that the best measure of felt recoil was gun velocity. Modern thinking leans toward gun kinetic energy, which is proportional to velocity if the guns are the same weight.

1911Tuner · Sep 9, 2015

Originally Posted by JohnKSa View Post
......When you hold the slide closed, the slide doesn't reciprocate with respect to the frame, but it does move in recoil with the gun and the shooter's hand. The momentum initially goes into the slide and barrel since they are locked together. They will, as a result, initially have the same velocity until something impedes one or the other.This is a statement that demonstrates a fundamental lack of understanding of the science behind this topic

And the subject is the slide's velocity and momentum...not the momentum transferred to the frame and the hand via the springs.

I know, which is why it's a waste of time trying to communicate with you (I applaud JohnKSa for even trying!)

And both of you are still trying to ignore an outside force that opposes the slide's acceleration from the git-go.

I'll try one more time, and then I'll give up.

Momentum will be conserved only in the absence of outside force. Once an outside force is met, momentum changes. If one end of an action reaction system meets with an outside force, its momentum is no longer equal to the other side...and once that momentum has been lost, it can't be regained without a new force.

The instant the slide starts to move, it meets with three outside forces. The recoil spring...the mainspring...and the hammer's mass.

If you stab the brake briefly when the car comes off the line...that's the mainspring and hammer.

If you keep your foot on the brake, and gradually increase pressure during the dash to the finish line...that's the recoil spring.

Those outside forces not only affect acceleration, they affect velocity and momentum.

Recoil (often called knockback, kickback or simply kick) is the backward momentum of a gun when it is discharged.

And "kick" only happens when the gun is being accelerated. Once acceleration ends, all movement...both gun and bullet...is momentum. And momentum is the after-effect...not actual acceleration.

Once the bullet has left the barrel, the action side of the action-reaction event is over. As far as the gun is concerned, it may as well have never been there. There is no longer an "action" in play...and without action, there is no reaction.

You should be ashamed of the false information you spread to the readers of this thread

Then you should take it up with one J. E. Bell...and actual rocket scientist who explained it all to me when I was 17 and full of questions on the subject. If I could put you in touch with him, I would...but he's been dead lo these many years.

When I asked him to explain why a gun kicks...his first statement was: "Because force accelerates it backward" and he went on to explain that ends the instant that acceleration ends. Then, and only then, did he get into momentum and the conservation of same...and explained that momentum is not kick...but more like "afterkick" or movement after the recoil...for lack of a better term.

45_auto · Sep 9, 2015

1911tuner said:
Recoil isn't momentum at all, but I've said that all along.

Equal momentum is only possible in the absence of outside force, or in the presence of equal outside force. Thus, it's theoretical in a real gun firing real ammunition.

Get your physics from 1911tuner or the real world, your choice. If you also believe that momentum in a gun is theoretical, quit reading now!

But a bit of advice to everyone else: As it's been demonstrated, handgun recoil systems are pretty irrelavent, you can hold the slide closed with your thumb. Doesn't much matter what you believe or understand. But if you ever have to choose to stand behind a BIG gun with a recoil system designed by 1911tuner or one designed by Army engineers, DON"T choose the one designed by 1911tuner!

From the Engineering Design Handbook, Carriages And Mounts Series Recoil Systems, US Army, 1969:

http://www.dtic.mil/dtic/tr/fulltext/u2/830281.pdf

The math doesn't copy very well, but there's a simple derivation of the dynamics of recoil on page 1, paragraph 2:

The dynamics of recoil presents a study in the conservation of momentum.
....

The forces tending to separate two bodies are equal
and opposite in direction
....

m1v1 = m2v2 Equation 1(c)

This principle is directly applicable to the recoil activity of guns where one side of Equation 1(c) represents the momentum of the recoiling parts and the other side represents the total momentum of the projectile and propellant gases moving in the opposite direction.

45_auto · Sep 9, 2015

1911tuner said:
Once acceleration ends, all movement...both gun and bullet...is momentum.

More gobbledygook. The rest of the world believes that movement after acceleration ends is inertia. Perhaps you could correct Newton and become a physics teacher. Can you cite even ONE verifiable reference for any of the stuff you spout?

Physics Classroom - Inertia and Mass

http://www.physicsclassroom.com/class/newtlaws/Lesson-1/Inertia-and-Mass

Newton's first law of motion states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia.

The slide is part of the recoil SYSTEM of the gun (not even going to try to explain a system and internal and external forces to you again). Do you believe that anyone is trying to deny that the momentum of the slide is affected by the barrel disengagement, mainspring compression, hammer inertia, firing pin (firing pin spring extension after primer strike ADDS to momentum of slide), etc?

Then you should take it up with one J. E. Bell...and actual rocket scientist who explained it all to me when I was 17 and full of questions on the subject. If I could put you in touch with him, I would...but he's been dead lo these many years.

Perhaps you should have listened better or taken better notes. But there are many actual rocket scientists still alive who I would hazard to guess have an understanding of physics at least equal to J.E. Bell (sorry, never heard of him) who could enlighten you if you would try to learn.

Jim Watson · Sep 9, 2015

And "kick" only happens when the gun is being accelerated. Once acceleration ends, all movement...both gun and bullet...is momentum.

I don't know about that.
Try this little gedankenexperiment:
Put your gun in a free recoil mounting like a ballistic pendulum. Fire it by remote control.
It will promptly accelerate to a recoil velocity determined by the gun/bullet momentum balance.
Place your hand behind the gun so that you stop the gun at its full recoil velocity after the bullet is departed. Kicks, doesn't it? Yet the acceleration phase of recoil was over.

MEHavey · Sep 9, 2015

It’s said that, according to the law of aeronautics and
the wingspan and circumference of the bumblebee, it
is aeronautically impossible for the bumblebee to fly.....
-------
However, the bumblebee, being unaware of these
scientific facts, goes ahead and flies anyway.”

Just shoot the gun.
Adjust as required.
:evil:

45_auto · Sep 9, 2015

It’s said that, according to the law of aeronautics and
the wingspan and circumference of the bumblebee, it is
aeronautically impossible for the bumblebee to fly ...…

However, the bumblebee, being unaware of these
scientific facts, goes ahead and flies anyway.”

Another internet rumor.

A little research is your friend, helps keep you from making silly statements.

http://www.snopes.com/science/bumblebees.asp

Claim: Scientists once proved that bumblebees can't fly.

FALSE

http://rationalwiki.org/wiki/Bumblebee_argument

Unfortunately (for the pseudoscientists), the laws of physics do not in any way forbid bumblebee flight; there are no papers that deny bumblebee flight, and no scientist has done so in a lecture, except, perhaps, ironically. To put it simply, it is possible to "prove" that a bumblebee cannot fly if you perform an extremely crude calculation (like forgetting to take into account things like the rate of flapping, the rotation of the wing, or the action of vortices), but a full aerodynamic calculation (to say nothing of getting all empirical and watching a bumblebee fly) will show that the bumblebee's flight works perfectly fine.

In fact, bumblebees simply flap harder than other insects, increasing the amplitude of their wing strokes to achieve more lift, and use a figure-of-eight wing motion to create low-pressure vortices to pull them up.

45_auto · Sep 9, 2015

1911tuner said:
And the subject is the slide's velocity and momentum...not the momentum transferred to the frame and the hand via the springs.

As a side note, exactly where (if not the slide) do you believe that the momentum being transferred to the frame and hand via the springs comes from? Exactly what physical part of the gun do you believe is compressing those springs if not the slide?

Have Newton's Laws been revised since I took engineering mechanics? Is momentum no longer conserved?

Schaum's Engineering Mechanics (1962):

I was really hoping to ignore this thread, but the amount of incorrect information being posted by some members is unbelievable.

MEHavey · Sep 9, 2015

Re Bumblees said:
A little research is your friend, helps keep you from making silly statements.

45_Auto, has this all gotten to the point that we've lost
our ability to see sardonic humor?

Of COURSE bumblebees can (an occasionally do) fly.
And the back-of-the-envelop calcs that said they couldn't
has loooooong been a physicist's jest at the folly of over-
simplified mathematical modeling.

Hence it's relevance to the last 2-3 pages of posting/counterposting.
:evil:

[and just in case you missed it...] :evil:

again

murf · Sep 9, 2015

all this "bumblebee" talk is confusing. think i'll just tread water instead.

hope you got an answer to your questions, mikemeyers.

luck,

murf

Walkalong · Sep 9, 2015

It's a shame we can't have this debate politely. It is always interesting until folks start aiming answers at individuals and not the information put forth.

Strength of slide return spring in a 1911

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