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so we are comparing water to shot ballistics now?

if there is any gain or loss as to the velocity through choking, would be miniscule to the shot to shot natural variation in ballistics.

 

i doubt there would be any system to distinguish from choking additional speed and shot variation.

 

i can roll up a hosepipe, does that mean i can roll up my gun?

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Dont get me wrong, i`m all for educating people.

 

So the cip and Saami guidelines have different criteria for there test barrels. some are choked some are not. i looked into this recently and most test barrels are CYL choked.

both CIP and SAAMI have different non compatable methods of measuring speed of shotshells.


:lol::lol::lol: Why would you want to roll up your gun? ???:whistling::whistling::whistling:

 

to put it in a washing machine.

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In terms of a scientific question I would say yes to both, if you impede something then you will increase the force needed to move it therefore the pressure build up from the expanding gasses will increase which is an increases in potential energy.

 

Once this potential energy is released because the wad has left the choke it will push the wad with more energy and the gas escaping will push back on the shoulder with more force.

 

A greater build up of pressure is potential energy and that energy has to go somewhere as energy cannot be destroyed only transferred.

 

Now and this is a big now would the differences ever be felt on the shoulder or seen in real life?

 

Answer no, it would be seen by some sensitive scientific measuring device but not by the shooter unless the choke was the size of a Biro and then the barrels would explode first.

 

But the theory of increased velocity and recoil is provable by formulas just the difference is so negligible it means nothing to us as shooters.

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In the case of a crimped hosepipe there is a constant flow of water, so obviously it has to speed up as it passes through the resriction.

If there was a constant flow of shot along a tube (think shot blasting or similar?) then again the shot would have to speed up as it passes the restriction at the end.

 

In a shotgun though, there isn't a constant flow of shot - but a discrete shot column moving along the barrel.

In this case the first few pellets at the front are probably sped up as they get pushed through by being kicked up the backside by the shot column. On the other hand the pellets at the back don't get this momentum behind them, so they probably get slowed down by the restriction?

So my guess is that the net effect is very little but the tighter choke leads to an increase in spread of velocities.

 

Whatever actually happens, as most above have said it will be too small to be ever noticed by the shooter.

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The hosepipe analogy works because of the expanding gasses, they are pushing the shot along and when the shot reaches the choke this causes a greater resistance meaning more force needed to pass the smaller constriction therefore building up the pressure of the expanding gasses which is the length of the barrel.

 

CIP give different figures for lead and steel because the shot does not pass through the choke as easily causing greater pressures. It's the same principle with tighter chokes just the difference is academic and easily covered in the safety margin therefore not an issue but the difference is there even though it is small.

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The hosepipe analogy works because of the expanding gasses, they are pushing the shot along and when the shot reaches the choke this causes a greater resistance meaning more force needed to pass the smaller constriction therefore building up the pressure of the expanding gasses which is the length of the barrel.

 

 

You might well be right, but isn't the powder normally burnt in the first 14inch?? or 18inch?? of the barrel? In this case, the shot wouldn't be being "pushed" along any more but is actually starting to deccelerate?

 

But then again there will still be a certain pressure of gas behind the shot to push it along, even when it has stopped accelerating.

An interesting thought excercise :hmm:

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You might well be right, but isn't the powder normally burnt in the first 14inch?? or 18inch?? of the barrel? In this case, the shot wouldn't be being "pushed" along any more but is actually starting to deccelerate?

 

But then again there will still be a certain pressure of gas behind the shot to push it along, even when it has stopped accelerating.

An interesting thought excercise :hmm:

 

Modern powders are used up in the first 10 inches of barrel, after that it's all down hill!

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the powder is burned in under the first 2" of the chamber. the pressure peak is in a varied of microseconds. i have loads tested, one "popped" at 3 the other 3.5 microseconds. that was the height of the main pressure peak, not the "on the way down from the main pressure peak".

 

after the main pressure peak, its loosing pressure all the time.

 

once the main pressure peak has completed, there is no more energy (ie powder thats burning) being applied. one of the variables of reloading is the amount of powder. ie how much energy can be applied to the shot / slug/bullet etc.

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Wow! What a reply, i thought my mail box had a hic-up.

I am learning that there is defiantly a cross between science & the black art on this sort of subject & my conclusion & what seems to be the consensus is!: Buy cartridges with a bigger load.

Thanks guys, Nice debate. :good:

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Wow! What a reply, i thought my mail box had a hic-up.

I am learning that there is defiantly a cross between science & the black art on this sort of subject & my conclusion & what seems to be the consensus is!: Buy cartridges with a bigger load.

 

Thanks guys, Nice debate. :good:

 

i wouldnt say that. science and the black arts or the art of common sense.

 

the FPS on the side of the box are usually a suggestive speeds. some manufacturers love to "big" up there shells to make them sound good.

the idea of choking to increase speed is highly speculative at best.

 

now, what does all this mean in the real world? / grass roots club shooting? ........ not a sausage.

 

buy a shell you`d like to shoot,

shoot it !

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The hosepipe analogy is invalid because the medium (water) is constant as is the force propelling it (your local pressure) and its molecules are in adhesion with one another and are both pulling and pushing one another, nowhere near what happens with a propellant bang and its effect on ejecta.

 

Recoil is as Newton has proved the product of gun weight V speed and weight of the projectile. Nothing else has a material scientifically measurable role. Recoil suppressors work by altering the time span of the recoils delivery which can be felt but the recoil itself cannot be altered scientifically.

 

If choke gave shot a measurable kick up the R's, then we could have a barrel made that after 18" goes from Cylinder to Quarter then immediately to Half choke eventually arriving at Super Full, culminating not to say cultivating a series of magical FPS increases which would be as miraculous as achieving perpetual motion for free. So in simple terms you could load a shell for 1300 FPS but throw it out at 1400 thus disproving Newtons Law !

 

You could argue that choke in fact slows down velocity, think of 20 people walking briskly through a door all in order, now imagine they're told to break rank and try and get through willy nilly. It is guaranteed that you'd get bottlenecks.

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I do take the point about burn rate, fast burn rate powders are not going to be the same as slow burn rate powders. If the gas is still expanding or the powder has not completely burnt then the hosepipe analogy works as energy is still being produced. The pressure will drop after the first few inches as the gas is now filling the void left by the wad travelling down the barrel and the wad now has momentum, but stop the wad moving and the pressure increases again as long as the powder is still burning or the gas still expanding. Gas is a fluid and as such restrict its flow rate you will increase its pressure over not restricting its flow rate down the same barrel with the same burn rate.

 

I understand you are slowing down the projectile but in doing this you are also increasing the potential energy behind it to be released. I also take the point if the reduction in velocity of the wad is greater than the potential energy produced by the expanding gas you will have a reduction in velocity rather than an increase.

 

I have read in the past that the move to slow burn rate powders to give greater velocity, the powder should just finish its burn as soon as the projectile leaves the muzzle. Whether anyone actually produces a cart like this I have no idea but I have seen published work on it that seemed to prove it. So maybe my first answer was over simplistic.

 

The point made about Newton’s law is flawed, 1300 FPS is a measure of velocity and you are discounting pressure in your analogy. The pressure the shell generates would increase behind the wad if you restrict its moment, if you let go of something with 10 psi behind it and then something with 20 psi behind it surely there would be an increase in velocity? It’s not perpetual motion just one way of increasing potential energy stored behind the wad to be released. But as I have said it is a balancing act between the reduction of the current velocity and the increase in pressure build up and if a very fast burn powder it would probably result in a decrease in velocity if at the end of the barrel. But expanding gasses need somewhere to go and if they cannot go somewhere then the pressure increases, so therefore does the potential energy stored behind the wad. As energy cannot be destroyed only transferred the increase in potential energy has to go somewhere once released.

 

Recoil is in 2 phases that feel like one to the shooter, the initial jolt propelling the projectile down the barrel and then from the release of pressure once the wad leaves the barrel. NASA use solid state rockets, nothing more than a tube burning a solid propellant with hot gases leaving a tube. The release of the escaping gasses is a measurable force and because of Newton’s law it will be in the direction of the shooters shoulder. As I said it is an academic post so I am not saying it is going to knock your teeth out or you would even feel it, but it still can be measured and the greater release of pressure the greater the force.

 

Muzzle brakes come in 2 types one that has a surface that stands proud of the muzzle so the escaping gasses can impart its energy onto this surface pushing the gun forward to counteract the rearward direction of the recoil so the force of this gas does exist.

 

The other uses baffles to dissipate the energy of the expanding gasses before the projectile leaves the barrel, interestingly if the last type are too efficient then it does greatly reduce the velocity of the projectile. This seems to suggest that harvesting too much of the gases at the end of the barrel before the projectile has left is detrimental to projectile velocity. So it could be suggested that the gasses still have their part to play whilst the projectile is still in the barrel.

 

As I have said it is just an academic post I don’t think for one second you would notice any difference other than with very sensitive test equipment and I am just thinking out allowed rather than proclaiming I am right.

 

I am finding it Interesting to think about though and not bothered who is right or wrong. :)

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As I have said it is just an academic post I don’t think for one second you would notice any difference other than with very sensitive test equipment and I am just thinking out allowed rather than proclaiming I am right.

 

I am finding it Interesting to think about though and not bothered who is right or wrong. :)

 

I agree with that. :good: Was good to have an interesting discussion without any toys having to leave the pram.

 

Just a thought but one of those super slow motion cameras could possibly see any difference between say full choke and cylinder (if there is any).

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I do take the point about burn rate, fast burn rate powders are not going to be the same as slow burn rate powders. If the gas is still expanding or the powder has not completely burnt then the hosepipe analogy works as energy is still being produced. The pressure will drop after the first few inches as the gas is now filling the void left by the wad travelling down the barrel and the wad now has momentum, but stop the wad moving and the pressure increases again as long as the powder is still burning ( if this is the case the powder is not buning at the same rate as it was before,the pressure is so low it "most likely" wont make a difference ) what is often mistaken is when unburned powder is pushed through the barrels by hot gasses, and is still smouldering not burning. this is caused by "lack of pressure" or too small a main pressure peak. or the gas still expanding. Gas is a fluid and as such restrict its flow rate you will increase its pressure over not restricting its flow rate down the same barrel with the same burn rate. in this case the gas produced is always limited, thats due to the minimum ammounts of powder in each cartridge.

 

Efficient cartridges, burn up all the energy (powder) in the chamber, and expell only hot gasses. inefficient cartridges, expell hot gasses, burning powder, and this is often seen, if you`ve shot in the dark, with some bakal / record cartridges they are spectacular.

 

I understand you are slowing down the projectile but in doing this you are also increasing the potential energy behind it to be released (the powder / energy should have been all used up). I also take the point if the reduction in velocity of the wad is greater than the potential energy produced by the expanding gas you will have a reduction in velocity rather than an increase.

 

I have read in the past that the move to slow burn rate powders to give greater velocity, (the move to slower burnrate powder os to apply more energy / more gas to the application. the slower burnrate powder is to have a~ 0.5 - 1microsecond shift of the main pressure peak, more powder means more gas, but slower application, ie within pressure limits....) the powder should just finish its burn as soon as the projectile leaves the muzzle. Whether anyone actually produces a cart like this I have no idea but I have seen published work on it that seemed to prove it. So maybe my first answer was over simplistic.

 

The point made about Newton’s law is flawed, 1300 FPS is a measure of velocity and you are discounting pressure in your analogy. The pressure the shell generates would increase behind the wad if you restrict its moment, if you let go of something with 10 psi behind it and then something with 20 psi behind it surely there would be an increase in velocity? It’s not perpetual motion just one way of increasing potential energy stored behind the wad to be released. But as I have said it is a balancing act between the reduction of the current velocity and the increase in pressure build up and if a very fast burn powder it would probably result in a decrease in velocity if at the end of the barrel. But expanding gasses need somewhere to go and if they cannot go somewhere then the pressure increases, so therefore does the potential energy stored behind the wad. As energy cannot be destroyed only transferred the increase in potential energy has to go somewhere once released.

 

Recoil is in 2 phases that feel like one to the shooter, the initial jolt propelling the projectile down the barrel and then from the release of pressure once the wad leaves the barrel. NASA use solid state rockets, nothing more than a tube burning a solid propellant with hot gases leaving a tube. The release of the escaping gasses is a measurable force and because of Newton’s law it will be in the direction of the shooters shoulder. As I said it is an academic post so I am not saying it is going to knock your teeth out or you would even feel it, but it still can be measured and the greater release of pressure the greater the force.

 

Muzzle brakes come in 2 types one that has a surface that stands proud of the muzzle so the escaping gasses can impart its energy onto this surface pushing the gun forward to counteract the rearward direction of the recoil so the force of this gas does exist.

 

The other uses baffles to dissipate the energy of the expanding gasses before the projectile leaves the barrel, interestingly if the last type are too efficient then it does greatly reduce the velocity of the projectile. This seems to suggest that harvesting too much of the gases at the end of the barrel before the projectile has left is detrimental to projectile velocity. So it could be suggested that the gasses still have their part to play whilst the projectile is still in the barrel.

 

As I have said it is just an academic post I don’t think for one second you would notice any difference other than with very sensitive test equipment and I am just thinking out allowed rather than proclaiming I am right.

 

I am finding it Interesting to think about though and not bothered who is right or wrong. :)

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