Recoil Gedankenexperiment...

housemap

Does the weight of the person using the firearm have a large effect on muzzle velocity ?

thx

Cass

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.

jap gt

housemap wrote: »

Does the weight of the person bullet usinged in the firearm have a large effect on muzzle velocity ?

thx

maybe thats what he/she meant

pedroeibar1

ezridax wrote: »

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
P

Sparks

But they'd mass more and therefore require more energy pedro, so would it even out?

Cass

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
P

Brilliant :D

As long as it refers to balistics. I thought there was an agenda against fat gits. I would have taken offence.

Sparks

ezridax wrote: »

I thought there was an agenda against fat gits. I would have taken offence.

You would have had to have taken a number.
And the fat ISSF gits would get first dibs because we wind up wearing spandex.




And yes, it's as daft-looking as it sounds.

housemap

I was just reading this interesting article here

http://en.wikipedia.org/wiki/Physics_of_firearms

This bit mislead me

Since the mass of the bullet is much less than that of the shooter there is more kinetic energy transferred to the bullet than to the shooter.

It gave me the impression there is a set amount of kinetic energy that is divided between shooter/firearm and bullet upon discharge depending on the weight of each so that the greater the weight of the shooter the less kinetic energy they gain and the more the bullet gains.

However I think they meant that there is no total set amount of kinetic energy, that the bullet depending upon its weight will gain a set amount of kenetic energy and muzzle velocity, and so will the shooter/firearm.
So the bullet will always have muzzle velocity X and the shooter/firearm will have velocity Y which will go up or down depending on their weight (but will not actually result in a velocity in most instances as the energy is absorbed by the shooters body)

So yea the weight of the shooter has no effect on muzzle velocity,
thx guys

pedroeibar1

Sparks wrote: »

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?
P.

rrpc

In answer to the OPs question, the answer is yes because heavier people are better at shouting their mouths off, so get a higher muzzle velocity as a consequence.

Cass

pedroeibar1 wrote: »

A big arse would be pushed forward by the propellant gases, thereby providing a good flange or seal around the projectile....................... other factors, such as the projectile crapping itself at the time of explosion, thereby dampening the propellant, producing a slower burn. ..............

Stop, seriously, i'm p***ing myself here.:D


Ah, God bless a slow TV night. This is much better.

tac foley

housemap wrote: »

Does the weight of the person using the firearm have a large effect on muzzle velocity ?

thx

Well, a heavier person may well squeeze the trigger harder, thus making the bullet go a lot faster.

Actually, I think you'll find that the transfer of proportional kinetic energy from the rifle to the person takes place during the recoil process, and recoil is a function of the mass and velocity of the cartridge plus the propelling gases. Remember that gas has mass, too. A heavier bullet in a larger calibre produces more recoil energy - in other words, the 'kick' from the gun is bigger. If you are built like a leprechaun then you'll feel it more than if you are a lard-ass gossoon.

All the energy required to send a bullet on its way up the bore is produced by the rapid deflagration of the propellant powder in the cartridge case, and has absolutely nothing to do with the weight of the shooter.

I respectfully suggest that you read the article until you have the theory firmly emplanted in the ould noddle.

If lighter people could shoot further then you'd be having ten-year-olds shooting .50cal long-range rifles out to three miles - and getting knocked arse over head with every shot, too. whereas the lard-ass shooting beside them would have his bullet falling out of the sky at a hundred yards.

tac

dCorbus

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!

Cass

dCorbus wrote: »

.......... about the same as ezridax's, ..........!

HEY! :eek:


I knew it. Ye're all calling me fat..........................



.................. i'm not saying its untrue, but no need to be mean about it.:D

dCorbus

Pots & Kettles, my good man!:P

:rolleyes:

dCorbus

the answer is yes because heavier people are better at shouting their mouths off, so get a higher muzzle velocity as a consequence

Shouldn't that particular phenomenon be more correctly termed: "Guzzle Verbosity"?

dCorbus

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!

FISMA

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?

Sparks

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

housemap

FISMA wrote: »

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.

FISMA wrote: »

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

Sparks

housemap wrote: »

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.

Dunno 'bout that - firing a lee enfield feels like trauma to my shoulder

WallysWorld

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.

Sparks

Okay, it's a thought experiment, but it's an interesting one...

WallysWorld wrote: »

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.

I still don't think that's true. The force on the bullet comes from the gas pressure on the back of the bullet from the propellant burning in the chamber. But that pressure is going to be (for all intents and purposes) even throughout the chamber, and the bullet is not attached to the rifle; so what's happening is that the gas in the middle is pushing on the rifle on one side and the bullet on the other with the same amount of force. Push the rifle and you're not pushing the bullet because it's not connected to the rifle. So it doesn't matter whether you've embedded the rifle butt in a mountain or whether it's on an air hockey table with no friction; the speed of the round relative to the rifle is going to be the same either way. And since we're not talking about pushing the rifle towards the bullet, but either (a) holding it still, or (b) letting the rifle move backwards, you can't even talk about pushing the rifle forwards fast enough to compress the gas behind the round and thus push the bullet indirectly.

You could measure this - sit the rifle in a bench vise and fire a round and chrony it; then sit the rifle in a batch testing rig that slides backwards easily and fire a round and chrony it. You'd have to fire more than one round, more than likely, to get rid of the minor variations between each round, but I'd bet a danish that the two speeds would be the same.

cavan shooter

Butt:D is the bullet not gone down range (all be it very small distance) by the time recoil is felt.?? ie. the only effects felt on it is friction and gravity

Sparks

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).

pedroeibar1

Sparks wrote: »

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...
P

Tackleberrywho

http://www.rticl.com/html/industry.html

A little light reading.

In regards to shooting, I know two guys who shoot the same rifle, both shoot as well as each other, one is a good 5stone heavier than the other guy.

When I was young I was skinny 11 stone, my grouping was reasonable. Now it is better and I am over 14stone.

I attribute this to practice,practice,practice............not being a fat cnut;)

Sparks

pedroeibar1 wrote: »

No so sure, Sparks, what about barrel flip?

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.

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.

Tackleberrywho

Sparks wrote: »

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

Sparks

Tack;
(1) constancy is not connected to the dimensionality of the property being measured, but to whether or not it's changing;

(2) you just said that speed is a vector hence it's called velocity. It isn't. We're not talking about velocity at all here, we're talking about speed, the scalar measurement.

Vegeta

Sparks wrote: »

the speed of the bullet relative to the barrel.

Yes it's all relative.

I agree Sparks that relative to the chamber and therefore barrel, it does not matter what way the gun is being held. The round will travel the same speed

Consider 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