The Great Thrust Vector Debate

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Pressure does not cause recoil.

If nothing escapes the system then there can be tremendous pressure and there will still be zero recoil--zero movement for that matter.
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That is true, however, when recoil does occur, it is the result of force on the breechface through the case head. That force comes from the gas pressure over the area of the rearward surfaces. A force does not manifest itself because of some distant action.
If it is not the gas pressure producing the force, then exactly what is?
 
If one exerts pressure on a movable object, it tends to move. We're wandering into semantics now.
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Exactly--semantics--you really meant to say that when you apply FORCE to a movable object it tends to move. ;)

Seriously, it is important. Pressure doesn't imply motion. Air up a tire--it doesn't move. Blow up a balloon--it stays stationary. Fill up an air tank with a compressor--no motion. Scuba tanks stay put even when full.

Recoil results from motion. That means that pressure isn't the answer. You can apply all the pressure you want but until something moves ain't nothin' happenin' recoilwise. It's the motion that generates the recoil. A big part of this is that people are using the word pressure as if it means the same thing as force. Maybe it does to some extent in common usage, but if you mix terms as they are scientifically defined in the attempt to solve a scientific problem the results are going to be confusing.

You can't ignore the semantics of a technical problem and still expect to make sense of the solution.
 
If it is not the gas pressure producing the force, then exactly what is?
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RJ357,

F=ma

Force = mass times acceleration.

Pressure has no mass. Pressure has no acceleration.

The recoil comes from the MOTION of the MASS of the bullet and other ejecta.

It may come as a shock, but Newton was right... ;)
 
A big part of this is that people are using the word pressure as if it means the same thing as force.
Click to expand...
We can use pressure here, because we are talking about specific areas (like a breechface) that the pressure is acting against. If the area is fixed in size, then a particular pressure will always result in a particular force.

The pressure inside an oxygen cylinder results in a force inside, outward against the cylinder walls. The reason the cylinder moves if you put a hole in the side is because you have reduced the force on one side at that spot. The force on the opposite side is greater and so it moves in that direction.
 
JohnKSa -
Pressure over an area is force. If you have pressure in a chamber, you have force against the sides of the chamber.
 
JohnKSa,

Blow up a balloon--it stays stationary.
Click to expand...

Once the pressure stabilizes, until then the sides expand away from each other. Like the breechface of an autoloader (and the bullet itself), the balloon walls are not fixed in space.

But, yes, the rearward-moving case exerts a force on the breech, and force and pressure are not the same thing. (Or are they? ;) ) Breechface thrust is usually measured, however, in psi or cup, if I'm not mistaken...

Pressure has no mass. Pressure has no acceleration.
Click to expand...

So, what causes the bullet to move forward? :confused:
 
Tamara -

Pressure is measured in psi (pounds per square inch) or cup (copper units of pressure).

Force is measured in pounds.
 
Tamara - Thank You!
Your post-
In clarification, however, what pushes the breechface back is the case....
Click to expand...
and follow up posts better said what I was trying to say / what I thought was going on.

JohnKSa - thank you as well.

So what I'm reading is [ correct me please if wrong] even a primed case , no pwdr, no wax , nothing - just a empty primed case will exert force against the breechface from what gases are caused by the primer only.
 
RJ357,

Correct. PSI and CUP are merely measurements of force over a given area. Which is what pressure is. N'est ce pas?
 
Tamara -
Pressure has no mass. Pressure has no acceleration.
Click to expand...
So, what causes the bullet to move forward?
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Hey thanks!, I think that will help make my point.

Maybe it's the same thing that makes the slide and barrel move backward.

And could that be, let's see, oh I don't know, a force due to PRESSURE??

JohnKSa -
Force = mass times acceleration.
Click to expand...
Force also = pressure times area
The recoil comes from the MOTION of the MASS of the bullet and other ejecta.
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And where does the motion of those come from?
It must also be true then, that the bullet's motion comes from the recoil of the slide. No?
And where does the recoil come from in that case?
It may come as a shock, but Newton was right...
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Yes I am familiar with Newton's 3rd law. It is not an explanation, but a description of how objects behave. It does not concern itself with the source or type of force, only with the magnitude and direction of the force vectors.
 
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Outstanding!

Good gawd! There are some smart folks on this forum...If nothin' else, it lays waste to the notion that we "Gunnies" are a bunch of slobbering,
redneck morons who drive around lookin' for somethin' to kill.

I'm gonna try to simplify a few things and see if it makes sense to anybody but me.

Fact: In order for recoil/slide movement to occur, the BULLET must move.

Fact: The bullet and the slide/barrel assembly START to move at the same time...at the instant of ignition...disregarding the nanosecond required
for the inertial resistance of each component to be overcome. Once the
process has started...movement starts.

Fact: Regardless of how small or large the amount of forward "pull" the bullet exerts on the barrel during passage, it still exists, and can't be discounted.

Fact: No matter how small or large the effect that the case has on the greater slide and barrel mass during gas expansion...it exists and can't be discounted. EVERYthing means SOMEthing...

So far, most of the discussion has been concentrated on the bullet and the
slide/barrel assembly acceleration, and the lowly expendable component...
the brass case...has largely been ignored.

Here's a little something thrown in that may require close consideration:

The brass case is also a projectile during the firing process. Its acceleration
is contained by the breechface...but it's still a projectile.

HYPOTHETICALLY...obtain a barrel with an extremely tight chamber...one that would require as much force to chamber a cartridge as the bullet passing through the barrel. There is no slide in this hypothetical experiment...only the barrel and the cartridge. Suspend the loaded barrel
and heat the primer to the ignition point. Which projectile will be accelerated faster...the heavy one, or the lighter one? In this, the heavier
bullet has become the recoiling component...the slide... and the case has become the bullet...no?

The vector is the force of the expanding gas that is pushing in opposite directions on two points of resistance..the heavier of which tends to resist that force vector to a greater degree than the lighter one, and the barrel will "recoil" FORWARD rather than backward as the "bullet" exits the chamber end.

Note to Grump: Yep...I think that we may be getting close to a balanced vector too...We were just approaching it from different directions.

Okay...Everybody take two Excedrin and think about it a little more.:D
 
Grumble

Howdy Lee!


Nahhh...Jim's just a "Low Profile" kinda gent, and didn't wanna get tangled up in the ragin' debate on this one. I'll move the other thread to this forum
in a few. Had to let the Collies do their mornin' constitutional....and
they do a right smart job of herdin' the cats around here. It's a sight, I tell ya! Pore ol' cats don't know whether to stand still, shoot marbles, or go for their guns.:D
 
OK. Scrap my old hypothesis. :D There is normally pressure on the breechface.

How about this.

Since the bullet is attached to the barrel, recoil can't occur, because just as much pressure is being exerted forward against the bullet/barrel as there is backward against the breechface. The locking lugs are absorbing all that energy, I guess. Normally the barrel is free to move backward with the slide, perhaps only overcoming a bit of friction against the bullet at the very beginning of its movement.

So simple, now that I think about it. :banghead:

Of course, I could be completely wrong again. ;)
 
I think I'm right with this last one, Tuner.

But I'd like to hear someone prove me wrong. :)
 
Right or Wrong

Middy said:

I think I'm right with this last one, Tuner.

FWIW, I do too.
________________

But I'd like to hear someone prove me wrong.

Aye! There's the rub. Proving a theory requires experimentation
...sometimes a lot of it, and from several different approaches in order to cover all the angles. That runs into time and money. Until a theory is PROVEN right OR wrong...it's still just a theory.

As the late, great Yogi Berra put it: (so simply)

"In theory...theory and practice are the same. In practice...they ain't."

Cheers all! Be back this afternoon...

Tuner
 
The brass case is also a projectile during the firing process. Its acceleration
is contained by the breechface...but it's still a projectile.
Click to expand...

We were just talkin' about that before you got back. Check the five or six posts before yours. :cool:

The breechface has inertia imparted to it and is set in motion by a cartridge case that is recoiling from newtonian forces, as well as having the pressure of expanding gasses acting on it. Since it is not fixed in space, it is trying to move, too, just like the bullet. (Set off the cartridge outside of the gun and watch the brass case depart the premises due to the rapidly expanding gasses inside, right?)
Click to expand...

The brass is recoiling in that direction because a projectile and a bunch of gas just went off in the other direction. Newton tells the brass to get moving, so it does, shoving the breechface out of its way and hopping politely out of the ejection port (after banging its little head on the ejector.)
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Checkin'

Howdy Tam. You said:

We were just talkin' about that before you got back. Check the five or six posts before yours.

Yeppers....My post was mainly a recapped, condensed restart.
Kinda like startin' over from point B...:cool:

In agreement with it too...but my pore ol' punkin' head is bangin' on me
and I gotta go see MamaTuner to mow for her.

Later on!

Tuner
 
A clear analysis of any situation is often mistaken for pessimism, altruism, or just being a Smart A$$:rolleyes:

Get a Glock:D :D :D

Does a Glock or any type of locked breech, albeit with a barrel hood, have the same lock up thrust vectoring as the 1911



Back to a question of does the barrel push back on the slide by way of the lugs or does the pressure against the breechface cause the slide to pull the barrel back.

Test to show that would be to get a cut away slide with a slot in the top to show the recoil lugs and have a few barrels with varying fits of the lugs, i.e. sloppy or extremely tight and with a high speed vid record the firing.

Now who has a 1911 we can cut up????
Who has the vid cam???




My take is the brass is not a projectile, but a seal and it takes a force from the gas pressure and directs it to the breech face and like a rocket it forces the slide and the barrel back.





You have to be smart to be a SmartA$$
 
Pressure in and of itself is inert. Think of an aerosol can. What causes movement is when something is moveable, the pressure will act on it and whatever else is containing it but first something has to move or the pressure stays contained and is inert.
 
This thread is like "the hurrier I go - the behinder I get".

Okay I may not have had Physics, I have been exposed to the Laws in other subjcts ...and dropped stuff on my foot tho'. :p

Here is where I am stuck. I'm still back at the empty case with a live primer only stage.

I still think there is a correlation to case head hitting the breech to get this whole 'movement " thingy started.

I thought the gases that resulted from the firing of primer were considered "mass" . So this primer only case is chambered , and upon firing gases are released down the bbl and the opposite and equal reaction exerts the case aginst breechface. Granted not a lot , still it happens.

When I used the Speer rubber bullets , more "mass". The weight of rubber , increased pressure of gases because they were more "resticted". The wax bullets had more felt recoil and would cycle. I have no idea of the weight of wax vs rubber bullet, , the open mouth of case was pushed into the warm paraffin to a cetain depth. So MY thinking is a tighter seal / crimp resulted in more resistance for gases to escape. Human feel could not measure this slight difference.

Since I don't know , I'm still stuck at the basic primer fired case. Actions were designed to funtion a certain way, in this case the 1911 style. So have to wonder if the basic design was figured first then metallurgy , springs , links and such built to withstand the loading.

Gotta run to class....back later . I get to tear something up :)
 
This thread needs pictures, vector diagrams especially. Each component gets its own diagram. The bullet, case, barrel, slide, link, etc. Remove the locking lugs from the barrel and pin the barrel into the frame. The slide will still move (with far more force than I want to hold in my hands) even with a fixed barrel.

The locking lugs ensure that the barrel recoils with the slide, keeping the breech locked until gas pressure has dropped to safe levels, then the link cams the barrel down, allowing the lugs to unlock and the slide to continue to retract.

Bore out the rifled portion of the barrel to larger than .451" and the pistol will still cycle. I apologise in advance if I further confused the issue.

Edit: Just read the other thread. Jim does a far better job describing things.
 
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