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Recoil Gedankenexperiment...
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09-09-2010 09:24PM#1
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I don't mean to be ignorant, but What?
Are you sure you worded that question right?
A persons weight has absolutely NO BEARING on muzzle velocity.Forum Charter - Useful Information - Photo thread: Hardware - Ranges by County - Hunting Laws/Important threads - Upcoming Events - RFDs by County
If you see a problem post use the report post function. Click on the three dots on the post, select "FLAG" & let a Moderator deal with it.
Moderators - Cass otmmyboy2 , CatMod - Shamboc , Admins - Beasty , mickeroo
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I don't mean to be ignorant, but What?
Are you sure you worded that question right?
A persons weight has absolutely NO BEARING on muzzle velocity.
Yes it does. A heavy person would be a tighter fit in the barrel so there would be a proper seal thus ensuring the projectile would block the gases more efficiently and obtain maximum propulsion!!:D:D
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pedroeibar1 wrote: »Yes it does. A heavy person would be a tighter fit in the barrel so there would be a proper seal thus ensuring the projectile would block the gases more efficiently and obtain maximum propulsion!!:D:D
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Brilliant
:D
As long as it refers to balistics. I thought there was an agenda against fat gits. I would have taken offence. Forum Charter - Useful Information - Photo thread: Hardware - Ranges by County - Hunting Laws/Important threads - Upcoming Events - RFDs by County
If you see a problem post use the report post function. Click on the three dots on the post, select "FLAG" & let a Moderator deal with it.
Moderators - Cass otmmyboy2 , CatMod - Shamboc , Admins - Beasty , mickeroo
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But they'd mass more and therefore require more energy pedro, so would it even out?:D
Haven’t really got the time to go the distance on this one, Sparks, but my premise is based on fat, which is more flexible and weighs considerably less than muscle/bone.
A big arse would be pushed forward by the propellant gases, thereby providing a good flange or seal around the projectile. On exiting the muzzle, the force from the rear on the rear would cease and the fat flange would become more streamlined and thus provide a more aerodynamic shape for the projectile.
There are other factors, such as the projectile crapping itself at the time of explosion, thereby dampening the propellant, producing a slower burn. However, a longer barrel would (could? ) overcome this. Get my drift?
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Well, based on the "knowledge" i've just gained from reading good ol' wikipedia, i have calculated that my own muzzle velocity is considerably more than IRLConor's, slightly more than rrpc's, about the same as ezridax's, and slightly less than sparks'!:D:D:rolleyes: Itwasn'tme's muzzle velocity has decreased proportionately to his new training regime.:rolleyes: (Or is it all the other way around:D)
There was me getting a new barrel on my .308 to increase the muzzle velocity, when little did I know that all it would take would be a few extra trips to Mickey D's to supersize me, and not the barrel.
Figgy should open a burger joint - He'd get more business that way and would increase all our muzzle velocities without any of that messing around with machinery!
And then there's the new HPS Supersized Half-Pounder triple-decker with extra swiss!0 -
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On exiting the muzzle, the force from the rear on the rear would cease and the fat flange would become more streamlined and thus provide a more aerodynamic shape for the projectile.
And if the projectile was a bit dim would that then be a: HPBT?
A Hollow Point Butt Tail?
Must......stop......now......
Good night, seattle!0 -
The article appears to mostly be concerned with the Law of Conservation of Momentum (LCOM) and Newton's Third Law: action and reaction pairs.
When fired, the firearm basically has two reactions. First the bullet goes forward and the firearm goes back. Second the bullet twists (say) clockwise and the firearm twists counterclockwise.
The force ON the person BY the firearm is equal and opposite to the force ON the firearm BY the person - that's Newton's Third Law.
Also, momentum MUST, I say MUST, be conserverd. The LCOM is more near and dear to a Phyicist's heart than anything, even the Law of Conservation of Energy.
Anyhow, momentum is conserved. Momentum, p = mv. The massive shooter has a small recoil speed and the fast bullet has a little mass. The masses and speeds balance. Note that in p = mv there are no squared terms so neither speed nor mass dominate.
Kinetic Energy depends upon mass and speed squared. Thus, when determining KE, speed, really, really matters (get it - really^2)
KE is conserved only in an ellastic collsion, which this is not. This "collision" is inellastic. Collision defined as an energy exchange.
I think you are trying to find out which bullet would have a greater muzzle velocity:
(a) Rifle secured in a vice, bolted to a table, bolted to the Earth, and fired.
(b) Rifle secured in a vice, bolted to a table, on frictionless ice, and fired.
Kind of like a big guy vs a smaller person shooting a firearm. One gets kicked back more than the other.
Was this the question?0 -
Thing is, in this case, the shooter's mass is irrelevant to the frame of reference of the bullet and rifle - the relevant force is between the rear of the chamber and the rear of the bullet, so bench vice or frictionless ice, the bullet will be going at the same speed every time relative to the rifle.
When the shooter stops the rifle flying back with recoil, he's not accelerating the bullet - he's transferring the rifle's part of the energy from the propellant into the ground.
So in theory at least, every shot you fire moves the world 0 -
The force ON the person BY the firearm is equal and opposite to the force ON the firearm BY the person - that's Newton's Third Law.
Thats true but thats not what is counter intuitive.
The force on the bullet (caused by expanding gases after powder burns) is equal to the force on the shooter/firearm (caused by expanding gases after powder burns) , I would imagine this would lead the average person to wonder why if the forces are equal are the effects so different - the shooter just feeling a slight jolt while the object struck by the bullet suffers severe trauma.I think you are trying to find out which bullet would have a greater muzzle velocity:
(a) Rifle secured in a vice, bolted to a table, bolted to the Earth, and fired.
(b) Rifle secured in a vice, bolted to a table, on frictionless ice, and fired.
Kind of like a big guy vs a smaller person shooting a firearm. One gets kicked back more than the other.
Was this the question?
Yes exactly 0 -
Dunno 'bout that - firing a lee enfield feels like trauma to my shoulderI would imagine this would lead the average person to wonder why if the forces are equal are the effects so different - the shooter just feeling a slight jolt while the object struck by the bullet suffers severe trauma. 0 -
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pedroeibar1 wrote: »:D
the force from the rear on the rear would cease and the fat flange would become more streamlined and thus provide a more aerodynamic shape for the projectile.
Ha ha, perhaps appropriately I'm crapping myself here that is one of the best constructed sentences I thought I'd never read!
I presume the op means Newtons law, equal and opposite forces and all that. So if a fat fella fires a rifle theres more mass opposing the force of the bullet exiting the barrel than if a dude a couple of stone lighter holds and fires the same rifle. It makes sense in that the fat **** provides a greater force to oppose the opposite force of the bullet but in reality I'm sure its actually non existent as far as any practical application.0 -
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In human terms cavan, yes (unless you're shooting an old air rifle); in physics terms, you're zooming in to look at the few microseconds between the primer igniting and the round leaving the barrel (after that point, there's no linkage of any kind between round and rifle and so it doesn't matter what happens to the rifle after that from the bullet's point of view).
No so sure, Sparks, what about barrel flip?
Also, there is friction .....and torque. While the bullet technically is not fixed to the barrel wall, it is in contact with it to a limited extent, thus there is some friction. (Is that not why air gun users have oil?) When the propellant ignites there is a torque element – for every action there is an equal and opposite reaction – hence recoil and some torque in a grooved barrel. The mass of the projectile and the mass of the gun determine recoil – e.g. WW Greener’s rule of 98. Also, in a SxS, the recoil will throw the right barrel to the right and the left barrel to the left since the axes of the barrels are respectively situated to the right or left of the centre of gravity, thus influencing recoil.
It’s a wonder nobody brought up inertia...........
I did NOT start this thread!
I’m leaving now...
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Doesn't affect the speed of the bullet after it leaves the barrel. And really, doesn't affect the speed at all, just the direction.pedroeibar1 wrote: »No so sure, Sparks, what about barrel flip?Also, there is friction .....and torque. While the bullet technically is not fixed to the barrel wall, it is in contact with it to a limited extent, thus there is some friction. (Is that not why air gun users have oil?) When the propellant ignites there is a torque element – for every action there is an equal and opposite reaction – hence recoil and some torque in a grooved barrel. The mass of the projectile and the mass of the gun determine recoil – e.g. WW Greener’s rule of 98. Also, in a SxS, the recoil will throw the right barrel to the right and the left barrel to the left since the axes of the barrels are respectively situated to the right or left of the centre of gravity, thus influencing recoil.
It’s a wonder nobody brought up inertia...........
I did NOT start this thread!
I’m leaving now...
Oh no you don't
And yes, all those things are correct, but they're not affected by whether the recoil is absorbed by a shooter/bench vice/whatever or whether it's just left knock the rifle around.
Trick is, look at things from inside the rifle, considering only the inside of the chamber, the gas and the bullet. In that frame of reference, the speed of the bullet is constant. If the entire frame (ie the entire rifle) is sent flying around by the recoil, it'll affect where the barrel points but not the speed of the bullet relative to the barrel.0 -
Doesn't affect the speed of the bullet after it leaves the barrel. And really, doesn't affect the speed at all, just the direction.
Oh no you don't
And yes, all those things are correct, but they're not affected by whether the recoil is absorbed by a shooter/bench vice/whatever or whether it's just left knock the rifle around.
Trick is, look at things from inside the rifle, considering only the inside of the chamber, the gas and the bullet. In that frame of reference, the speed of the bullet is constant. If the entire frame (ie the entire rifle) is sent flying around by the recoil, it'll affect where the barrel points but not the speed of the bullet relative to the barrel.
The speed of the bullet is not constant it is a vector quantity hence termed in velocity. speed is a scaler quantity with no magnitude 0 -
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Yes. Same as every other time you fire the rifle. I mean, if you grab the rifle, how do you think you stop the rifle moving backwards? By pushing against the planet.So where does the force that would normally push the gun backwards go? Is it absorbed by the earth?
Except that by preventing the rifle moving under recoil you do absolutely nothing to the gas pressure. It's pushing out in all directions at once and equally (let's leave aside turbulence and gas fluid pressure waves just for the momentI don't think so- the force that would normally push out in every other direction is not absorbed by the barrel. If it was the barrel would do no good. Instead what happens is that the gas channelled because it is prevented in going outwards, perpendicular to the bore - it can only push in 2 directions; forwards, pushing the bullet out, and backwards, pushing the rifle back. Surely by reducing the places the gas can go even further, you will increase the pressure? I doubt you could measure the difference in speed, but I think there has to be a difference. ). The sides of the chamber all resist through the tensile strength of the steel, as does the back of the chamber; the only avenue left is via the barrel, pushing (and pushing around) the bullet in the process. Recoil's irrelevant to this: think about it, if the bullet wasn't in the rifle, would you still get recoil? Yes, and the same amount; which means that the force on the bullet is going to be the same as well.
Actually, it wouldn't; increasing the mass of the bullet would lead to a decrease in speed of the bullet; that's why we measure muzzle energy not muzzle velocity when deciding what the firearm/not-a-firearm cutoff is for airguns, so that you can't go from a toy to a firearm by loading a heavier pellet.Look at it this way: increasing the mass of the bullet would increase the energy imparted to the shooter. Why should it not work the other way around?0 -
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Yes it's all relative.:DConsider though the speed relative to the target (chronograph at fixed point near target). If the chamber is moving away from the target at time of firing (say on the back of a very fast truck driving directly away from the target) and the bullet speed is relative to the chamber then it certainly makes sense that the bullet will arrive on target at a lower speed than a setup where the chamber does not move away from the target.
Now from all the high speed shots or super slow motion shots I've seen, it always seems that the round has left firearm before recoil (a force driving the chamber away from the target) takes effect. So I doubt it effects speed in a meaningful way
Sort of contradicting yourself??
but.....
Consider a flatbed truck travelling at a constant 100kph on the trailer of which a ball is dropped from a position behind the cab. It does not fall onto the road behind the trailer because the ball has inertia, i.e. the ball is moving at the same speed as the truck. (Inertia being the resistance of any physical object to a change in its state of motion or rest.)* Apply the same logic to a bullet; the ignition speed of the propellant is so fast the bullet’s speed relative to the breech is zero. So there will be no material difference.
However, I do admit that the bullets path, like a ball being dropped off the trailer i.e. outside, will be subject to the much greater forces of friction and gravity. That path can best be described as a load of parabolics.
*a feature common/well-known to some posters on these Boards
I reall have to do some work...............
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Well, it does - in that if the projectile isn't in the barrel in the first place, there'll be no force applied to it
What I'm saying is that the force applied to the rifle is the same as the force applied to the bullet regardless of whether or not the bullet is there.
Look at it on an atomic level. A gas is just atoms flying about. The number of atoms per unit volume is the pressure. So right after the propellant burn, there are propellant atoms flying all over the place behind the round, bouncing off the walls of the chamber and the back of the bullet. Every time one of them bounces, it imparts energy to the surface it bounces off.
Ones that bounce off the back of the bullet push the bullet; ones that bounce off the back of the chamber create the recoil. But if there's no bullet, you still get atoms bouncing off the rear of the chamber.
Hmm. But you wouldn't get so many bounces in a given unit of time, so yes, you'd have less recoil if you'd an open chamber (not thinking about the wad you normally get in a blank, for the moment). But that still doesn't mean that the bullet will get less or more force if the rifle is allowed to recoil or not; the number of bounces the back of the bullet gets is dependant on the speed of the bullet relative to the barrel only; once the bullet leaves the barrel, no more bounces.0 -
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When it comes to Rockets, true they are happy in Space. However, since there's no oxygen to cause combustion, you have to bring it with you - which is desperately expensive.
At some point you're chasing your tail. You have to bring like oxygen to combust the fuel. But now you need more fuel, to carry that oxygen. But then, you need more fuel, to accelerate the fuel to Mach 20 something... You get the idea. I think it costs $10,000 to get a gallon of water into low earth orbit.
Anyhow, it's best to say accelerate in Physics. The "m" word - move, is a bad word in Physics. Since all motion is relative, all Physics cares about is whether or not you are accelerating.
Anywho...
Here's a simple image
When the fuel ignites it expels gasses for propulsion. Remember, that objects accelerate in the direction of the unbalanced Force.
There are Forces everywhere inside of the bell. Up and down Forces pretty much cancel out. In the diagram above, the gasses push on the left hand side of the bell/motor/whatever it is called. However, the gasses that go out into space do not push on anything. Thus, the LHS force is unbalanced and the rocket accelerates to the left. Cool huh? 0 -
I always was very interested in rockets and propulsionWhen it comes to Rockets, true they are happy in Space. However, since there's no oxygen to cause combustion, you have to bring it with you - which is desperately expensive.
At some point you're chasing your tail. You have to bring like oxygen to combust the fuel. But now you need more fuel, to carry that oxygen. But then, you need more fuel, to accelerate the fuel to Mach 20 something... You get the idea. I think it costs $10,000 to get a gallon of water into low earth orbit.
Anyhow, it's best to say accelerate in Physics. The "m" word - move, is a bad word in Physics. Since all motion is relative, all Physics cares about is whether or not you are accelerating.
Anywho...
When the fuel ignites it expels gasses for propulsion. Remember, that objects accelerate in the direction of the unbalanced Force.
There are Forces everywhere inside of the bell. Up and down Forces pretty much cancel out. In the diagram above, the gasses push on the left hand side of the bell/motor/whatever it is called. However, the gasses that go out into space do not push on anything. Thus, the LHS force is unbalanced and the rocket accelerates to the left. Cool huh?
so can we now state that SPEED is not the correct word and Velocity is
And that a round is accelerating in a barrel until it is retarding & is a vector Quantity as it has magnitude
This has to be the weirdest thread in a long time 0 -
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