Hey Tuner, xray of 1911 firing

[Grump]

Grump...

Quote:
Take the slide stop out of your 1911 and tell me how well you can unlock the barrel/slide by pulling back on the slide, eh?
Of course it won't "unlock." The slidestop crosspin is what the link uses to draw the barrel vertically out of engagement with the slide. That's why the crosspin is inserted through the open hole in the link. Now...Let's see if you can tell us why the slide will only travel about a quarter-inch with the slidestop removed. Hmmm?

Don't help him! Let him answer.

No fair, you declared time's up after less than two hours. I haven't even been on the board, and I don't post 6.xx times per day on a 7-day-week average, either.

Perhaps we're talking past each other, but the slide don't go back without a link because it's still locked to the barrel. Physical interference. Maybe you're talking about some "sticky" effect of the pressure of contact, but I still submit that of the 19,000 or whatever PSI of a .45 ACP round's peak chamber pressure, bullet drag on the barrel is truly there, can be measured, and ain't likely to be more than 2,000 PSI of it. The rest is gas pressure pushing equally in all directions including against the bullet and the breech. Bullet is moving, so the slide/barrel assembly moves backwards under recoil.

Betcha that high-speed photography of a 1911 firing a nice high-pressure blank will still show the slide pulling backwards and engaging the barrel's locking lugs. No bullet pull there. The design lets the barrel/slide assembly be locked together just through simple geometry.

"Almost" being a blowback is as nonsensical as (but in the opposite direction from" being a "little" pregnant. The pistol is a locked breech design, and the speed of the cycle is such that there is some residual chamber pressure left when the case clears the chamber on extraction. You can test the extraction "boost" of that pressure by firing the pistol without an extractor. Do .38 Supers work better this way than .45 ACPs?

I'm not the mathematician to calculate the resistive effect of the slide mass on its rearward movement. I'd be far more convinced if there were some real numbers attached to this argument. Why is it that I, a stupid attorney with not one college-level physics class, am the only one (it seems) to apply some rough numbers to this? Use all those degrees you have, guys!

This force can't be underestimated because it's doubtless the most powerful and resistive of the six. Pushing the bullet through the barrel requires more force than is required to overcome the resistance offered by all the others combined.

Come on, that's like saying "everybody KNOWS". It's a logical fallacy and unsupported by anything more than weak argument. Wish I could remember all that calculus as it applies to instantaneous acceleration problems. Your 22-lb recoil spring force dwarfs in contrast with the power of inertia when the time of force applied are measured in milliseconds!
[]

 

[1911Tuner]

Link?

I beg to differ. Remove the link from your barrel...assemble it completely...and manually draw the slide rearward. The barrel will fall.

Psssst! Grump! Keep lookin'. You've been wrong since you jumped into this one...and you get wronger with every post.

PS. You can't calculate it. The coefficient of friction is an empirical measurement...it has to be measured experimentally, and can't be found through calculations. If you'd paid closer attention in your high school physics class, you'd have known that.

It goes up...or down...depending on several factors. Materials of the contacting surfaces are only two. The load that is placed on either or both is the biggie. i.e. You can drag a board across a floor easily. If you place a 2,000-pound weight on top of it...it ain't so easy.

 

[Grump]

Try it upside-down, Tuner. Gravity substituting for a link doesn't prove the barrel and slide are unlocked when forward and in battery.

 

[Grump]

A "Thought Experiment" for this tiresome thread

Okay, brainflash (or fart, depending on your prejudices).

Two Yugos, parked and stationary. One is on clean dry pavement on earth, and one is on the moon on a perfectly flat sheet of water ice.

Propel your Crown Vic crash test dummy car into the rear of each of them, impact speed of 45 mph.

I betcha the difference in damage caused by "road drag" resisting the acceleration of the Yugo will be real, measureable, and tiny compared to the effects of inertia vs. inertia.

Where's the physics guy when we need one?

The time over which the force is applied is key here.

 

[1911Tuner]

Try it upside-down, Tuner. Gravity substituting for a link doesn't prove the barrel and slide are unlocked when forward and in battery.

Oh, I know. I just wondered if you did.

Your moon test is about as closely related to what we're discussing as a linebacker slamming into a quarterback. Impact momentum are the wild cards.

Grump...I know you're trying', and I'm tryin' to help you see this. I think that the reason you can't is because...with everything else moving backward, and happening so fast, you can't grasp how anything moving forward can have such a profound effect. I had to ponder on it long and hard before I understood it.

So I'll try again...just for the sake of understanding.

We've already established that the barrel is pulled backward by the slide. Right?

Read this next part carefully. Read it more than once if you need to. It usually takes three times for an unfamiliar idea to take root.

As the barrel is drawn rearward, the bullet is moving forward in the barrel. Both surfaces...bullet OD and bore ID...are slipping over one another at the same time. Bullet driven forward through the bore...bore surface pulled backward off the bullet. That it only lasts for a split fraction of a fraction of a second doesn't mean a thing.

While the bullet is in the bore and moving forward...and the barrel is being dragged backward...the cohesive friction between bore and bullet surface are resisting both parts and in both directions. Are ya with me here?

When you pull the cork through the pipe, the pipe's surface is resisting the cork's forward movement, and the cork's surface is resisting the pipe's rearward movement...EQUALLY.

So...Whatever force that is resisting one is resisting the other...in equal measure. If it takes X pounds of force to push the bullet in one direction, it requires the exact same amount of force to pull the barrel backward across the bullet's surface...because...the two events are occurring simultaneously.

Go and push a bullet through a barrel with a rod and understand just how much force is required, and then consider how much would be required to not only push it through...but to push it through in the time frame involved. No fair starting it with a hammer. Just drop it into the chamber...place the end of the rod against it...and push. Lock it into a vise if you want. Unless you have the upper body strength of a Sumo wrestler, you won't get the full diameter of the bullet into the leade. Go get help. Have two or three grown men try it.

 

[Iron bottom]

Correct me if I am wrong, Gentlemen. I am not a physics major.

As an example, lets accelerate a 3.5 oz barrel to 32 ft/sec in 1/1000 sec.
The force to do this will make the barrel seem to weigh 3,500 oz, or about 219 pounds. Double this to account for bullet drag. let's say 440 lbs of force on 1/4 square inch of lug. 16 times 440 will give 7040 pounds on the lugs.

Feel free to correct my math, laugh, hurl insults or whatever.

 

[1911Tuner]

16 times 440 will give 7040 pounds on the lugs.

Sounds about right. Of course, it will be higher at the beginning, when resistance is highest...and because the force required to accelerate the bullet will fall with an increase in bullet velocity, it will be lower just as the bullet is about to exit...but that sounds reasonable for an average number

 

[19112XS]

Go and push a bullet through a barrel with a rod and understand just how much force is required, and then consider how much would be required to not only push it through...but to push it through in the time frame involved. No fair starting it with a hammer. Just drop it into the chamber...place the end of the rod against it...and push. Lock it into a vise if you want. Unless you have the upper body strength of a Sumo wrestler, you won't get the full diameter of the bullet into the leade. Go get help. Have two or three grown men try it.

I've tried this and barely scored the jacket of a standard diameter bullet with an average barrel. Couldn't even drive it into the rifling.

 

[SDC]

Now, do it again, and explain to me how it is that this "huge force" is so weak that all it can do is carry the weight of a barrel forward against a recoil spring in any of the "blow-forward designs". If this "bullet pulling" effect was as strong as it's claimed to be, you either wouldn't be able to COCK one of those designs, or it would be a single-shot, because firing a shot would tear the barrel out of the receiver and launch it downrange.

 

[presspuller]

Now, do it again, and explain to me how it is that this "huge force" is so weak that all it can do is carry the weight of a barrel forward against a recoil spring in any of the "blow-forward designs". If this "bullet pulling" effect was as strong as it's claimed to be, you either wouldn't be able to COCK one of those designs, or it would be a single-shot, because firing a shot would tear the barrel out of the receiver and launch it downrange.

You just keep digging yourself a deeper hole don't you?

 

[SDC]

You just keep digging yourself a deeper hole don't you?

It's a simple question, so it should be simple to answer; do these laws of physics NOT APPLY in the blow-forward design, or is this "bullet-pulling force" simply being given WAY too much credit? The blow-forward principle has even been used in a .308-class rifle, the 7.5x53mm Swiss AK53; if a 1911 depends on "thousands of pounds of force" generated by the "bullet pull" of the .45 Auto cartridge, the "bullet pulling forces" generated in the AK53 must be on the order of MILLIONS of pounds, right?

 

[presspuller]

I can by no means explain things as simply as Tuner but I would think the amount of force required to push a bullet thru a barrel is about the same regardless of size.

 

[1911Tuner]

I would think the amount of force required to push a bullet thru a barrel is about the same regardless of size.

Theoretically true at least...but there are variables that would affect the final figure.

Bore diameter to bullet diameter. Land diameter to bullet diameter. Jacket material and thickness. Core material and hardness. All these things increase or decrease the bullet's resistance to being forced into the bore.

You just keep digging yourself a deeper hole don't you?

Yep he do...but for some reason I feel compelled to help him anyway. So...

Lord, gimme strength and help me find the words...

A basic law of physics states that we can't have force in one direction without an equal measure of force in the other. This is the essence of Newton's 3rd Law. Force forward equals force backward. Whatever force is imposed in one direction will be imposed in the other.

NEWS FLASH!!

This law applies to resistive forces as well as compulsive forces.

So, it follows that if X units of force are resisting in one direction, then X units of force will resist in the opposite direction. Force forward equals force backward.

I.E. If X units of force are required to pull the cork through the pipe, then X units are required to pull the pipe off the cork, because whatever resistance that the pipe offers TO the cork, an equal measure of resistance will be offered to the pipe BY the cork.

This is easy to understand if we perform the actions one at a time...slowly. If we anchor the pipe and pull the cork...or anchor the cork and pull the pipe...it requires the same force irregardless of which is being pulled. It becomes harder to understand when both events occur at the same time. It becomes harder still if both events are occurring at the same time and in a very short time frame...and it becomes even harder if they occur within a very short distance. It still happens...even though we can't SEE it happen.

There's no way to explain these basic truths away, except in your own mind. As to that...I'm firmly convinced that cats are aliens from another galaxy, sent here to enslave us and make us do their bidding...but until I can offer solid evidence of that...it remains no more than a theory.

If this "bullet pulling" effect was as strong as it's claimed to be, you either wouldn't be able to COCK one of those designs, or it would be a single-shot, because firing a shot would tear the barrel out of the receiver and launch it downrange.

No more than a blowback would be impossible to cock or that it would destroy the slide and shove it through your head. I don't know much about the blowforward device, but it would require some sort of positive impact surface to limit the barrel's forward travel...like the slide has in a blowback pistol...it would seem.

But, you have evolved. At least now you're admitting that the bullet does exert a forward drag on the barrel during its passage. That's something, at least. All we have to do at this point is to get you to understand the magnitude of the forces involved.

Go push a bullet through a barrel. We'll wait...

 

[1911Tuner]

I've tried this and barely scored the jacket of a standard diameter bullet with an average barrel. Couldn't even drive it into the rifling.

Now, just imagine what sort of force is required to drive that bullet to 800+fps in a little over 4 inches of barrel, and it'll give you an idea of what the locking lugs are enduring...shot after shot.

 

[SDC]

You don't seem willing to admit that the actual FORCE transmitted to the barrel in a blow-forward design (and, by necessity, in any OTHER design) can't possibly be much more than the force that's required to cock that firearm in the first place. Does it take hundreds, or thousands of pounds of force to cock a blow-forward design? No, of course not, otherwise it would never be adopted. That means that the force that's transferred to that barrel during firing must LIKEWISE be much less than what you're claiming.

 

[1911Tuner]

And neither does it take thousands of pounds of force to cock a blowback pistol...but if the slide didn't have a mechanical limit, the county coroner would have to pull it outta your head before callin' anybody down to ID your body...

 

[presspuller]

And neither does it take thousands of pounds of force to cock a blowback pistol...but if the slide didn't have a mechanical limit, the county coroner would have to pull it outta your head before callin' anybody down to ID your body...

Can't really argue that one.

 

[1911Tuner]

Can't really argue that one.

Give him time...

He keeps grasping at that same straw...and nobody ever said that it required thousands of pounds of force to cycle the gun. We've maintained that there are, however, thousands of pounds of force at work during the cycle...and that whatever force is required to accelerate a bullet from a standstill to over 800 fps through that very restrictive 4.1 inces of barrel is far more substantial than he and Grump realize.

 

[presspuller]

Like I said before, some things are like trying to teach a pig to sing, you waste your time and annoy the pig.

 

[LotI]

This is good!

Tuner, I am riveted!

 

[1911Tuner]

Lot....

Go to your room!

Easy, puller. Let's try to bring'em into the light. I have hopes that they'll understand it. I can feel a breakthrough comin'.

 

[peterotte]

Hi Folks.

I haven't done the math yet. Had to load up some rounds for a shooting session (rifle).

There is one facter that reduces the magnitude of the forward drag force acting on the locking lugs and that is the inertia of the barrel. (Very short time duration). I am planning on setting up a rig to actually measure the force required to drive the bullet through the barrel. I will use a hydraulic ram and simply record the pressure. This will take a while, so don't anybody hold your breath waiting!

If I may just add a comment here. It is difficult for anyone to picture in our minds the forces at play during the firing of a pistol. Things happen so fast and move so quickly. Even the way one holds the gun can effect it's operation. Some guns, if not held firmly, won't cycle properly.

Picture this, if you have a one pound weight resting on the floor, it will exert a force of one pound on the floor. If you now attach a string to it and pull upwards with a force of almost one pound, the weight will exert a force of almost nothing on the floor. Now if the string were to snap at this point, the weight will exert a momentary force of two pounds on the floor. (Suddenly applied load).

Regards all
Peter

 

[presspuller]

Well to be honest when I first opened this thread there was a LOT about the internal working during firing of a recoil opperated pistol that I did not completely understand, but you (Tuner) made it so simple to understand that the light came on completely.
While I can not put it into words as good as you or could never get the point across as good as you, I can say I understand it complety thanks to you.

I wish I was as positive as you on the outcome of this but I just don't see much hope.
I think you are wasteing your time.:banghead:

 

[1911Tuner]

Peterotte..When you measure the forces involved...remember the mention that you made of suddenly applied force...and that during the live operation of the gun, the bullet is not only being forced through, but it's being accelerated to over 800 fps in 4.1 inches of barrel.

Please, please...go on to explain the differences in kinetic friction and static friction...and that it requires more force to get something moving...or slipping...than it does to keep it moving.

One final point, if I may...before I turn it over to you.

The forces involved...some 20,000 pounds per square inch...are only operating for a very brief time. The resistance to initial acceleration is a big part of what causes pressures to peak so early and rapidly. At the instant of peak...whatever force is involved is what is borne by the lugs...engaged in a shearing action. As the bullet accelerates ever faster, the force required to keep it moving drops...and since force forward equals force backward...so does the force exerted on the breechblock...and consequently on the lugs.

So...Peak force on the lugs isn't maintained for any longer than peak pressure...and because pressure drops as the volume of the cylinder, or area behind the bullet increases...net force also drops.

So..If you can vary the speed of the bullet as you press it through the barrel...it would be helpful to report the difference between pressing it through slowly and pressing it through quickly.

 

[Carl N. Brown]

before the bullet leaves the barrel
We have two cylinders acting in two directions
under gas pressure: the cartridge case pressing back
against the slide, and the barrel (temporarily plugged
by the moving bullet) pushing its lugs forward against
the locking grooves in the slide. Or at least that is
what I see in the X-ray.