Physics help: Is this statement true?
- Thread starter dyl
- Start date
A jacketed bullet, at the same charge weight as a lead bullet, will have a lower velocity because the jacketed bullet has more friction with/against the barrel than lead. There will be less recoil because the bullet is going slower, not because of it's construction. Prolly not noticable though as the difference is small.
Niether general statment is true.
First: Jacketed bullets may or may not have lower muzzle velocity for the very reason mentioned: their initial friction imposes higher start pressures -- which in turn produce higher burn pressures in modern progressive-burning powders. If you then integrate the force/pressure profile down the barrel length to get work done on the bullet, jacketed bullets can easily come out ahead for a given powder (type) weight.
Second: Felt recoil is not just muzzle energy (i.e, 1/2bullet mass x muzzle velocity-squared). It is specific impulse: How fast was the force applied as the bullet accelerated. High acceleration at the start (e.g., with very fast powders) can therefore generate higher felt recoil even if muzzle velocities are roughly equal at the end.
Lotsa math here and every case will require individual calculations, and your head may wind up hurting more than your shoulder.
First: Jacketed bullets may or may not have lower muzzle velocity for the very reason mentioned: their initial friction imposes higher start pressures -- which in turn produce higher burn pressures in modern progressive-burning powders. If you then integrate the force/pressure profile down the barrel length to get work done on the bullet, jacketed bullets can easily come out ahead for a given powder (type) weight.
Second: Felt recoil is not just muzzle energy (i.e, 1/2bullet mass x muzzle velocity-squared). It is specific impulse: How fast was the force applied as the bullet accelerated. High acceleration at the start (e.g., with very fast powders) can therefore generate higher felt recoil even if muzzle velocities are roughly equal at the end.
Lotsa math here and every case will require individual calculations, and your head may wind up hurting more than your shoulder.
Recoil: JHP vs. Lead
Thank you. My apologies for not giving more information:
The original discussion this came from involved lead vs. JHP of the same weight and same charge.
I was really confused because I previously believed:
1) Recoil forces begin before the bullet exits the barrel - example: this is why lighter revolvers will shoot to different elevations with different bullet weights. The recoil arc is affected.
2) Muzzle velocity doesn't determine recoil - not between different calibers for sure. But within the same caliber and charge, powder type, that given amount of energy will be transferred to a faster (lighter) or slower (heavier) bullet. That is, assuming a complete burn for both.
Mehavey, yes you're right - I'm now feeling confused again over all the variables.
I thought that lower muzzle velocity typically correlates to more recoil - usually from heavier bullets - or from allowing a more complete powder burn.
So given the same caliber, bullet weight, powder, a complete burn for both, would slower muzzle velocity truly mean reduce recoil?
Something about the original statement made me think like a generalization was being made that was incorrect: lower velocity automatically means low recoil.
Thank you. My apologies for not giving more information:
The original discussion this came from involved lead vs. JHP of the same weight and same charge.
I was really confused because I previously believed:
1) Recoil forces begin before the bullet exits the barrel - example: this is why lighter revolvers will shoot to different elevations with different bullet weights. The recoil arc is affected.
2) Muzzle velocity doesn't determine recoil - not between different calibers for sure. But within the same caliber and charge, powder type, that given amount of energy will be transferred to a faster (lighter) or slower (heavier) bullet. That is, assuming a complete burn for both.
Mehavey, yes you're right - I'm now feeling confused again over all the variables.
I thought that lower muzzle velocity typically correlates to more recoil - usually from heavier bullets - or from allowing a more complete powder burn.
So given the same caliber, bullet weight, powder, a complete burn for both, would slower muzzle velocity truly mean reduce recoil?
Something about the original statement made me think like a generalization was being made that was incorrect: lower velocity automatically means low recoil.
All else being equal, the slower bullet will produce less recoil.
http://www.handloads.com/calc/recoil.asp
http://www.handloads.com/calc/recoil.asp
Felt recoil is only indirectly related to muzzle energy.
Recoil is created by the momentum of the ejecta, not their energy.
(m(bullet) * v(bullet)) + (m(powder) * v(powder gas)) = m(gun) * v(gun)
You can get the free recoil energy by using 1/2 * m(gun) * v(gun)^2
Notice the bullet velocity is not present (except indirectly from its momentum).
The less mass you throw out the barrel at the same velocity, the less recoil.
wncchester
New member
Recoil impulse starts when the first bullet moves, it does't wait until the bullet exits. And half the weight of the powder charge should be added to half the bullet weight for the calculations.
People tend to forget, formulas are not laws. They can help you estimate things, but cannot tell you the whole story. Take a formula that tells you how fast your bullet will go with a certain amount of a certain powder. It will get you close sure, but it cannot take into account things like bore tightness and fouling, things like that, so its not going to be able to tell you the exact velocity you will achieve. Same thing with a recoil calculator....
Common sense tells me that assuming the same charge and bullet weight, the bullet thats harder to push out the barrel will have more felt recoil.
Imagine, you have a ramrod type pole and a hollow tube fixed to a solid table. You have two cylinders, both weighing five pounds (each). One is an easy slip fit in the tube, and the other is a rather tight fit. You stick the smaller diameter cylinder in the tube, and give it a shove with the ramrod. The amount of traction your shoes require is the "felt recoil". Now you take the other and put it in, its a much tighter fit and harder to move. Take the ramrod and shove it down the tube... Its going to take a lot more traction on your shoes to shove this one down the tube, even if you push with the exact same amount of force.....
Common sense tells me that assuming the same charge and bullet weight, the bullet thats harder to push out the barrel will have more felt recoil.
Imagine, you have a ramrod type pole and a hollow tube fixed to a solid table. You have two cylinders, both weighing five pounds (each). One is an easy slip fit in the tube, and the other is a rather tight fit. You stick the smaller diameter cylinder in the tube, and give it a shove with the ramrod. The amount of traction your shoes require is the "felt recoil". Now you take the other and put it in, its a much tighter fit and harder to move. Take the ramrod and shove it down the tube... Its going to take a lot more traction on your shoes to shove this one down the tube, even if you push with the exact same amount of force.....
Lost Sheep
New member
Dacaur, could you go over that again, please?
You have
a hollow tube fixed to a solid table
two 5-lb cylinders (one a tight fit in the tube and one not so tight)
one ramrod type pole
you shove the cylinders into the hollow tube (one at a time) with the ramrod with the same force
How is the traction of your shoes different when you are applying the same force on the two cylinders?
I'm confused.
Or should I say "lost"?
Lost Sheep
You have
a hollow tube fixed to a solid table
two 5-lb cylinders (one a tight fit in the tube and one not so tight)
one ramrod type pole
you shove the cylinders into the hollow tube (one at a time) with the ramrod with the same force
How is the traction of your shoes different when you are applying the same force on the two cylinders?
I'm confused.
Or should I say "lost"?
Lost Sheep
PHYSICAL recoil is just a matter of the momentum of the material that exits the gun through the muzzle. That includes the bullet AND the powder; their individual contributions of momentum must be added together.
We typically have the velocity of the bullet, but not the velocity of the gases created by the burning powder. When the bullet exits the muzzle and uncorks the gases, the gases accelerate and actually blow past the bullet. This creates a significant thrust (recoil), just like a rocket engine does. That thrust is the product of the gases' weight and velocity. The actual velocity depends on the pressure and temperature of the gases as the bullet exits the muzzle. In its 2006 reloading pamphlet, Hogdon recommends using 4700 fps for the velocity of the gases in a shotgun. Powders that produce higher muzzle pressures typically produce more recoil. That is because (compared to a faster-burning powder) there is usually more of the slow-burning powder needed to make the higher exit pressure and it leaves the gases at a higher temperature when they exit. In magnum rifles, recoil can be nearly half due to the powder.
FELT recoil is a different matter. As mentioned in a previous post, the speed with which the momentum builds-up is important to what the shooter feels. That is because the shooter is relatively "soft" compared to the gun steel or even the rubber in many recoil pads. So, the shooter's hand or shoulder actually deforms some WHILE the bullet's momentum is building-up in the barrel and AFTER the bullet exits and the "rocket effect" occurs. How fast that deformation occurs is what the shooter actually feels.
For example, consider the difference in what it feels like to catch a one ounce slug going 1000 fps verses a 1000 ounce (62.5 pound) lead ball going only 1 fps. One is a killing shot while the other is a bump that probably won't leave a bruise. But, the PHYSICAL momentum is the same. The difference is that the tissue cannot transmit the force of the slug through the whole body fast enough to absorb the momentum with the whole body, so there is local damage (wounding), but the 62.5 pound ball is moving so slowly that the whole body ends-up moving from the impact without any part of the body getting badly deformed.
Differences in felt recoil for the SAME amount of physical recoil in the SAME gun are just the result of how fast the recoil is being added by bullet acceleration and powder gas acceleration from a particular load , PLUS how the shooter's body deforms due to the shooter's grip strength, hand size, weight, and many other factors related to the SHOOTER. Compared to smokeless, black powder is noted for giving more of a "push" than a "sock", and bigger framed shooters are noted for being less sensitive to recoil than smaller framed shooters.
But, add something like bruising or arthritis to a shooter's hands, and the perception of recoil is magnified by how much a particular amount of recoil hurts the more sensitized nerves. So, there is still more to it than physical deformation of the individual shooter.
SL1
We typically have the velocity of the bullet, but not the velocity of the gases created by the burning powder. When the bullet exits the muzzle and uncorks the gases, the gases accelerate and actually blow past the bullet. This creates a significant thrust (recoil), just like a rocket engine does. That thrust is the product of the gases' weight and velocity. The actual velocity depends on the pressure and temperature of the gases as the bullet exits the muzzle. In its 2006 reloading pamphlet, Hogdon recommends using 4700 fps for the velocity of the gases in a shotgun. Powders that produce higher muzzle pressures typically produce more recoil. That is because (compared to a faster-burning powder) there is usually more of the slow-burning powder needed to make the higher exit pressure and it leaves the gases at a higher temperature when they exit. In magnum rifles, recoil can be nearly half due to the powder.
FELT recoil is a different matter. As mentioned in a previous post, the speed with which the momentum builds-up is important to what the shooter feels. That is because the shooter is relatively "soft" compared to the gun steel or even the rubber in many recoil pads. So, the shooter's hand or shoulder actually deforms some WHILE the bullet's momentum is building-up in the barrel and AFTER the bullet exits and the "rocket effect" occurs. How fast that deformation occurs is what the shooter actually feels.
For example, consider the difference in what it feels like to catch a one ounce slug going 1000 fps verses a 1000 ounce (62.5 pound) lead ball going only 1 fps. One is a killing shot while the other is a bump that probably won't leave a bruise. But, the PHYSICAL momentum is the same. The difference is that the tissue cannot transmit the force of the slug through the whole body fast enough to absorb the momentum with the whole body, so there is local damage (wounding), but the 62.5 pound ball is moving so slowly that the whole body ends-up moving from the impact without any part of the body getting badly deformed.
Differences in felt recoil for the SAME amount of physical recoil in the SAME gun are just the result of how fast the recoil is being added by bullet acceleration and powder gas acceleration from a particular load , PLUS how the shooter's body deforms due to the shooter's grip strength, hand size, weight, and many other factors related to the SHOOTER. Compared to smokeless, black powder is noted for giving more of a "push" than a "sock", and bigger framed shooters are noted for being less sensitive to recoil than smaller framed shooters.
But, add something like bruising or arthritis to a shooter's hands, and the perception of recoil is magnified by how much a particular amount of recoil hurts the more sensitized nerves. So, there is still more to it than physical deformation of the individual shooter.
SL1
I guess I forgot to mention that I dont believe a jacketed bullet will recoil less with the same charge as a lead bullet. Yes it has less velocity, but thats only because of the extra friction on the barrel. I believe in fact there will be more FELT recoil with the slower jacketed bullet.
Forget everything I said and ask yourself, WHY does the jacketed bullet have a lower velocity than the lead bullet when they have the same amount of energy behind them? Its due to the additional friction, which makes it harder to push down the bore, right? Now, answer this, why does a heavier bullet have a lower velocity than a lighter bullet when the have the same amount of energy behind them? BECAUSE ITS HARDER TO PUSH DOWN THE BORE. The jacketed bullet could be said to be, in effect as far as the physics go, simply a heavier lead bullet
If that still doesnt get ya, ill go back to the cylinder and tube analogy...
Well, obviously, the tube is a gun barrel, the loose fitting cylinder is a lead bullet, the tight fitting cylinder is the jacketed bullet, and you and your ramrod are the powder charge.
When you push against the cylinder (ignite) there are two forces at work here (at least, for the purposes of this demonstration). You are pushing against the 5lb cylender, but if you were not connected to the ground, the cylinder would go one way while you would go the other (equal and opposite reactions, right?) Your shoes are the other force, (which would be the case head, pressing back against the bolt, and eventually against you, the shooter), they try keep you from moving backward, the traction required would be felt recoil.
Given the exact same amount of energy exerted, because its easier to push the loose cylender (lead bullet), there is less force wasted going backward (recoil), so the looser cylender goes out of the tube faster ( a lead bullet will, generally, attain higher velocity given the same charge as a jacketed bullet, right?). The tighter cylinder (jacketed bullet) has more friction friction against the tube, so its harder to push out, the end result is not only less velocity when it exits the tube, but also more traction required to keep you from moving backward (more felt recoil)
Since the charge is equal, there is the same amount of energy in both instances, and that energy has to go someplace. Its either propelling the bullet, or its pushing against your hand or shoulder. Some will be converted to heat by the additional friction, but most of it will come back at you as recoil.
Back to the tubes and cylender analogy.... would you, as the powder charge be able to tell the difference between a tighter fitting 5lb weight and a looser fitting 10lb weight? All you know is that its harder to push the tighter fitting or heavier weight. In my experience, heavier bullets have more felt recoil. So if the jacketed bullet is simply, in effect, a heavier bullet, there is going to be more felt recoil.
I just blew your minds, right?
mrawesome22
New member
The problem with physics is that real world tests rarely match up to what the lab geeks predict.
The first atomic bomb measured, roughly, 10 times the energy output predicted by the "men in white".
Start low and work up slow.
Sent from MIUI using Tapatalk 2.
The first atomic bomb measured, roughly, 10 times the energy output predicted by the "men in white".
Start low and work up slow.
Sent from MIUI using Tapatalk 2.
If that were the case, you wouldn't be tapping on your Tapatalk.
Actually, not. Little Boy and Fat Man may have been differently Uranium vs Plutonium, and gun impact vs implosion
-- but they came out pretty much as predicted even being so totally different in fission design.
Now the first "dry" lithium(6) deuteride thermonuclear fusion device ("Bravo") caught them a bit shy of calculations by a factor of 2.5 (15 megatons vice predicted 6) -- but that was because the supposedly inert Lithium-7 isotope decided it wanted to come to the party.
Can't win`em all, don'cha know.
wncchester
New member
"All I need to know about science is.... the earth used to be flat but now it's round."
And that's a pertinent observation, scientists make mistakes too. Even in achient days they were quite intelligent but lacked some basic data in some areas so they got some things wrong, like a flat earth.
Move to today and note how many are quite sure we're having man made global warming (or cooling, they're not quite sure which,) and many are certain man is causing it and if we don't stop it we're all going to fall off the edge of the earth and ... whoops, I mean we're all going to fry because the "sky is falling!"
And that's a pertinent observation, scientists make mistakes too. Even in achient days they were quite intelligent but lacked some basic data in some areas so they got some things wrong, like a flat earth.
Move to today and note how many are quite sure we're having man made global warming (or cooling, they're not quite sure which,) and many are certain man is causing it and if we don't stop it we're all going to fall off the edge of the earth and ... whoops, I mean we're all going to fry because the "sky is falling!"
That's what you get for counting on common sense when you need a scientist, or at least someone who understands high school physics. Newton figured all this stuff out 400 years or so ago.
Lots of physics failures on this thread.
The example above has NOTHING to do with the recoil you would feel. The reaction between you, your ramrod, your shoes, and the floor would be analogous to the chamber pressure required to push the 5 pound cylinder down the bore. A .22LR has a chamber pressure of 24,000 PSI, while a .45ACP runs at 21,000 PSI. "Common sense" using your example would tell us that the .22LR has more recoil than the .45ACP.
In reality, the recoil would be proportional to the mass and acceleration of the projectile and has nothing to do with the force (chamber pressure) pushing on it, as a couple of others have pointed out.
A better example - find a barrel (needs to be a pressure vessel - a bomb container) strong enough to withstand the full pressure a cartridge can develop if the bullet does not move. Weld a plug into the barrel just in front of the chamber so the bullet can't move. Load it and pull the trigger.
You will have an UNGODLY amount of pressure in the chamber, but ZERO recoil because the bullet is NOT accelerating, therefore the gun is NOT accelerating in recoil. It will just sit there until you vent the chamber.
At that point, it will move in the OPPOSITE direction from where the gas is venting (accelerating), just like it moves in the opposite direction from what the bullet is accelerating when you fire it normally.
Firing a bullet down a barrel is just like firing a rocket engine, except that the rocket engine throws much smaller particles at a much higher velocity. The principles are the same.
As old Newton said, "For every action there is an equal but opposite reaction".
To the OP:
As a general rule (99% of the time) this is true. As others have pointed out, lead bullets have less friction so attain a greater velocity for the same charge weight. Assuming equal weight bullets and a constant length barrel, the bullet moving faster has a higher average acceleration.
Since Force = Mass x Acceleration, the rearward force (recoil) will be higher from the bullet that experiences the highest acceleration.
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dacaur,
The problem with your analogy of the tube and the plugs being pushed down it by a rod is that you are erroneously comparing the force of the push on the bullet with the recoil. In the situation of the gun, in effect, you are holding BOTH the tube AND the rod, so the force on BOTH of those is what you feel, NOT just the force on the rod. It is more like trying to hold the tube in one hand and the rod in the other and trying to force the plug down the tube by bringing your hands together. The friction on your shoes would not matter; you could be floating weightless in orbit and have the same situation.
Saying it another way, the force of the friction between the bullet and the barrel is trying to push the gun FORWARD, which is somewhat counteracting the force of the gases on the case head that is trying to push the gun back at you (creating recoil).
The total amount of momentum change in a FREE-FLOATING gun can be computed by adding-up the total amount of momentum change in the bullet and propellant. That is just the muzzle velocity of the bullet times the bullet's weight plus the velocity of the propellant gases as they escape the barrel (after bullet departure) times the weight of the propellant charge. Divide that sum by the weight of the gun, and you get the FREE recoil velocity of the gun when it fires that cartridge. Square that velocity, divide it by 2, and multiply by the gun's mass (in appropriate units) and you get the FREE recoil energy of the gun when firing that cartridge.
BUT, the gun is NOT free-floating since there is a shooter holding onto it (I hope). So, the REAL recoil velocity is somewhat less than what this calculation produces because the weight of PARTS of the shooter effectively adds something to the weight of the gun. That is almost impossible to calculate, because it depends on how much of the shooter's body parts "stack-up" behind the gun as it compresses them with the recoil. That depends on how hard the shooter is holding the gun, how much soft tissue is between the gun's handle and the shooter's bones, how heavy those parts are, etc. for a whole lot of different bones.
But, all that still doesn't really address FELT recoil. To understand that, you DO have to go back to the actual forces involved WHILE the bullet is going done the barrel AND while the gases are escaping after the bullet departs the barrel. That is, you need to consider the way that total momentum change builds-up over time.
The forces on the shooter are basically the force of the gases on the back of the case MINUS the force of the bullet friction on the bore until the bullet leaves the muzzle, which vary over time since the pressure is not constant and the bullet is accelerating. After the bullet leaves the muzzle, there is a period when the uncorked gases are accelerating down the bore and out the muzzle that produces the "rocket effect." The calculation of recoil from the rocket effect is more difficult to explain using only a description of the forces involved, because it involves a lot of gas dynamics and some non-intuitive understanding of how forces from accelerating gases occur on hard surfaces over which they pass. So, let's just talk about the time before the bullet leaves the muzzle.
When a cartridge is fired, the pressure builds to a peak and then decreases as the propellant is consumed and the space for the resulting gases is increased by the bullet moving down the bore. Most of the acceleration of the bullet occurs in the first few inches of the bore. The faster the powder burns, the less of the bore's length is used to achieve a particular fraction of the final muzzle velocity. The shooter can feel this difference, even though it happens quite fast, because it changes how the shooter's hands, arms, etc. are compressed by the recoil, and the shooter's nerves are sensing those compressions very quickly. So FOR THE SAME FINAL MUZZLE VELOCITY, a fast powder tends to give more of a "sock" and a slow powder tends to give more of a "push." That is because the bullet sees a higher PEAK pressure and accelerates faster in the early part of its trip down the bore.
But, as handloaders, we often compare loads with DIFFERENT muzzle velocities when we talk about using fast and slow powders. The idea is to not exceed the limit of PEAK pressure for the gun, so we use small charges of fast powders when we want slow muzzle velocities and larger charges of slow powders when we want fast muzzle velocities. With the SAME PEAK PRESSURE, the recoil force of the slower powder will reach about the same peak as for the faster powder, but will be higher than the fast powder's recoil force for MOST of the time, giving more change in bullet momentum and more total recoil. In addition, the larger charge weight of the slower powder will result in a higher pressure when the bullet leaves the muzzle, increasing the "rocket effect" by BOTH the greater velocity of the escaping propellant gases AND the greater weight of those gases (equal to the higher charge weight). So, magnum loads with slow powders may create about the same peak recoil force as light loads with slow powders, but the forces are high for a longer period of time, which affects how the shooter's body parts are compressed and what (s)he feels as "recoil." (This is still somewhat simplified, because about half of the propellant gases are already accelerating down the bore BEFORE the bullet leaves the muzzle. But, in handguns, the propellant weighs much less than the bullet. In rifles, the propellant might weigh half of what the bullet weighs or even more, so that can also contribute to FELT recoil before the bullet leaves the bore.)
SL1
The problem with your analogy of the tube and the plugs being pushed down it by a rod is that you are erroneously comparing the force of the push on the bullet with the recoil. In the situation of the gun, in effect, you are holding BOTH the tube AND the rod, so the force on BOTH of those is what you feel, NOT just the force on the rod. It is more like trying to hold the tube in one hand and the rod in the other and trying to force the plug down the tube by bringing your hands together. The friction on your shoes would not matter; you could be floating weightless in orbit and have the same situation.
Saying it another way, the force of the friction between the bullet and the barrel is trying to push the gun FORWARD, which is somewhat counteracting the force of the gases on the case head that is trying to push the gun back at you (creating recoil).
The total amount of momentum change in a FREE-FLOATING gun can be computed by adding-up the total amount of momentum change in the bullet and propellant. That is just the muzzle velocity of the bullet times the bullet's weight plus the velocity of the propellant gases as they escape the barrel (after bullet departure) times the weight of the propellant charge. Divide that sum by the weight of the gun, and you get the FREE recoil velocity of the gun when it fires that cartridge. Square that velocity, divide it by 2, and multiply by the gun's mass (in appropriate units) and you get the FREE recoil energy of the gun when firing that cartridge.
BUT, the gun is NOT free-floating since there is a shooter holding onto it (I hope). So, the REAL recoil velocity is somewhat less than what this calculation produces because the weight of PARTS of the shooter effectively adds something to the weight of the gun. That is almost impossible to calculate, because it depends on how much of the shooter's body parts "stack-up" behind the gun as it compresses them with the recoil. That depends on how hard the shooter is holding the gun, how much soft tissue is between the gun's handle and the shooter's bones, how heavy those parts are, etc. for a whole lot of different bones.
But, all that still doesn't really address FELT recoil. To understand that, you DO have to go back to the actual forces involved WHILE the bullet is going done the barrel AND while the gases are escaping after the bullet departs the barrel. That is, you need to consider the way that total momentum change builds-up over time.
The forces on the shooter are basically the force of the gases on the back of the case MINUS the force of the bullet friction on the bore until the bullet leaves the muzzle, which vary over time since the pressure is not constant and the bullet is accelerating. After the bullet leaves the muzzle, there is a period when the uncorked gases are accelerating down the bore and out the muzzle that produces the "rocket effect." The calculation of recoil from the rocket effect is more difficult to explain using only a description of the forces involved, because it involves a lot of gas dynamics and some non-intuitive understanding of how forces from accelerating gases occur on hard surfaces over which they pass. So, let's just talk about the time before the bullet leaves the muzzle.
When a cartridge is fired, the pressure builds to a peak and then decreases as the propellant is consumed and the space for the resulting gases is increased by the bullet moving down the bore. Most of the acceleration of the bullet occurs in the first few inches of the bore. The faster the powder burns, the less of the bore's length is used to achieve a particular fraction of the final muzzle velocity. The shooter can feel this difference, even though it happens quite fast, because it changes how the shooter's hands, arms, etc. are compressed by the recoil, and the shooter's nerves are sensing those compressions very quickly. So FOR THE SAME FINAL MUZZLE VELOCITY, a fast powder tends to give more of a "sock" and a slow powder tends to give more of a "push." That is because the bullet sees a higher PEAK pressure and accelerates faster in the early part of its trip down the bore.
But, as handloaders, we often compare loads with DIFFERENT muzzle velocities when we talk about using fast and slow powders. The idea is to not exceed the limit of PEAK pressure for the gun, so we use small charges of fast powders when we want slow muzzle velocities and larger charges of slow powders when we want fast muzzle velocities. With the SAME PEAK PRESSURE, the recoil force of the slower powder will reach about the same peak as for the faster powder, but will be higher than the fast powder's recoil force for MOST of the time, giving more change in bullet momentum and more total recoil. In addition, the larger charge weight of the slower powder will result in a higher pressure when the bullet leaves the muzzle, increasing the "rocket effect" by BOTH the greater velocity of the escaping propellant gases AND the greater weight of those gases (equal to the higher charge weight). So, magnum loads with slow powders may create about the same peak recoil force as light loads with slow powders, but the forces are high for a longer period of time, which affects how the shooter's body parts are compressed and what (s)he feels as "recoil." (This is still somewhat simplified, because about half of the propellant gases are already accelerating down the bore BEFORE the bullet leaves the muzzle. But, in handguns, the propellant weighs much less than the bullet. In rifles, the propellant might weigh half of what the bullet weighs or even more, so that can also contribute to FELT recoil before the bullet leaves the bore.)
SL1
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