This has caused some hot discussion around the club lately.
A shooter is shooting a event that requires a "Power Factor" that is bullet mass (g) times Velocity (fps)
of 120,000.
So..
If I use a light 120g bullet at 1000 fps, will it have more or less "felt recoil" than a 150g projectile at 800 fps
if fired in the same gun ?
(The power factor is the same for each load.)
It is not a simple answer......
Felt recoil, light vs heavy projectile
Moderators: pilkguns, m1963, David Levene, Spencer, Richard H
Re: Felt recoil, light vs heavy projectile
In Newtonian physics, force = mass x acceleration (f=ma) so whether you have a projectile that weighs 120 units travelling at 1000 units of speed, or a projectile that weighs 100 units travelling at 1200 units of speed, the force is still equal at 120000 units of force. Newton's third law states that every force has an instantaneous equal and opposing force - in this case recoil. As the force in both examples is the same, the felt recoil, in terms of absolute force, will be the same.
However, a faster accelerating projectile (a lighter unit travelling at higher speed) will provide a faster acceleration opposing the direction of travel than a slower, heavier projectile.
Small fast projectile = Short, snappy recoil
Slower, heavier projectile = Smoother, longer recoil - Whether the negligible difference is noticeable remains to be seen.
However, a faster accelerating projectile (a lighter unit travelling at higher speed) will provide a faster acceleration opposing the direction of travel than a slower, heavier projectile.
Small fast projectile = Short, snappy recoil
Slower, heavier projectile = Smoother, longer recoil - Whether the negligible difference is noticeable remains to be seen.
Re: Felt recoil, light vs heavy projectile
True, but we are not looking at Force (f=ma),
we are looking at Momentum (p=mv) or
maybe Energy (ke=1/2mv2).
we are looking at Momentum (p=mv) or
maybe Energy (ke=1/2mv2).
Re: Felt recoil, light vs heavy projectile
f=ma and p=mv are pretty much the same thing as you're still multiplying a mass and a speed, be it acceleration or velocity and the equivalence between ma and mv is the same. You can take the examlpes I've used and come to the same answer using either formula.
Re: Felt recoil, light vs heavy projectile
My non-scientific thoughts...
In pistols I prefer the recoil of heavy bullets going slower, I just like the softer slower "push' as opposed to the faster kick. But in rifles I prefer the recoil of lighter bullets going faster, heavy rifle bullets really seem to give you a good smack!
In pistols I prefer the recoil of heavy bullets going slower, I just like the softer slower "push' as opposed to the faster kick. But in rifles I prefer the recoil of lighter bullets going faster, heavy rifle bullets really seem to give you a good smack!
Re: Felt recoil, light vs heavy projectile
Force (f=ma) and Momentum (p=mv) although similar are not the same, the difference is Time.Shifty wrote:f=ma and p=mv are pretty much the same thing as you're still multiplying a mass and a speed, be it acceleration or velocity and the equivalence between ma and mv is the same. You can take the examlpes I've used and come to the same answer using either formula.
Recoil is a rearwards Momentum produced by projectile and expelled gas,
but we are looking at the perception of recoil or felt recoil.
Re: Felt recoil, light vs heavy projectile
We do not know the acceleration, so we do not know the force. But assuming the amount of powder is the same we can inititially assume the force levels are the same. Therefore the recoil force should be the same. (the difference in the muzzle velocity being of course that the same force is acting on a greater mass. Momentum is not the same as force. For example, as you travel through space while spinning on earth, you do in fact have momentum, but you do not "experience" it. You do "experience" force.)
Re: Felt recoil, light vs heavy projectile
The sensation of the softer push can be attributed to the heavier weight in the magazine. Next time you are at the range, see if you can detect a softer recoil with the first shot and the magazine full vs the last shot and the magazine empty.j-team wrote:My non-scientific thoughts...
In pistols I prefer the recoil of heavy bullets going slower, I just like the softer slower "push' as opposed to the faster kick. But in rifles I prefer the recoil of lighter bullets going faster, heavy rifle bullets really seem to give you a good smack!
If shooting high power rifle, it is possible the powder weight is a little more with the heavier bullet.
Re: Felt recoil, light vs heavy projectile
I thought it was fairly common knowledge among powerful rifle shooters that heavier bullets (at lower velocities) produced more recoil than the lighter bullets.
This is ONE of the reasons the U.S. went to the lighter 150 grain bullets in their .30/06 for the military.
This is ONE of the reasons the U.S. went to the lighter 150 grain bullets in their .30/06 for the military.
Re: Felt recoil, light vs heavy projectile
It was my "non scientific thoughts", but seeing as you wish to debunk them... My opionion is based on many pistols, some with and some without magazines over many years. In the last 20 years I don't think I have bought any factory centre fire ammo for either pistol or rifle as I reload for all of them. So I'd know if there was more powder behind a heavier rifle bullet than a light one and 99 times out of 100 the powder weight decreases as the bullet weight increases.mbradley wrote:The sensation of the softer push can be attributed to the heavier weight in the magazine. Next time you are at the range, see if you can detect a softer recoil with the first shot and the magazine full vs the last shot and the magazine empty.j-team wrote:My non-scientific thoughts...
In pistols I prefer the recoil of heavy bullets going slower, I just like the softer slower "push' as opposed to the faster kick. But in rifles I prefer the recoil of lighter bullets going faster, heavy rifle bullets really seem to give you a good smack!
If shooting high power rifle, it is possible the powder weight is a little more with the heavier bullet.
Re: Felt recoil, light vs heavy projectile
I apologize, I was not trying to debunk you. If what you are saying is true, then there must be some other forces acting that I am not accounting for.
Re: Felt recoil, light vs heavy projectile
If you check the OP, it's about "felt recoil" which is basically just opinion, not science.mbradley wrote:I apologize, I was not trying to debunk you. If what you are saying is true, then there must be some other forces acting that I am not accounting for.
Re: Felt recoil, light vs heavy projectile
You are missing the key points to the question, it is the same Power Factor (Momentum) for each load,David M wrote:A shooter is shooting a event that requires a "Power Factor" that is bullet mass (g) times Velocity (fps)
of 120,000.
So..
If I use a light 120g bullet at 1000 fps, will it have more or less "felt recoil" than a 150g projectile at 800 fps
if fired in the same gun ?
(The power factor is the same for each load.)
fired in the same gun.
So we need more powder in the light projectile to make the higher speed and may need to change the powder burn rate.
The burn rate or pressure curve of the internal ballastics for different powders will change felt recoil.
Also the heavy load gun weight will include the extra weight of the heavier projectiles.
As I said, it is not a simple answer......
Re: Felt recoil, light vs heavy projectile
David,
I believe that the "felt recoil" you are speaking of would be force, not momentum. Force and momentum are inversely related, but it takes force to get an object to have momentum. And, as stated above, we don't know the rate of acceleration so we can't mathematically solve this problem.
Also, why the differentiation of "felt recoil" and not actual recoil? Do you think that they might differ? If you want to know which has the greater "felt recoil", then just simply perform a blind test. No, you don't need to shoot blindfolded though those that have seen me shoot think it couldn't hurt :)
Joel
[Remember: velocity and acceleration are just a simple integration (or differentiation) away.]
I believe that the "felt recoil" you are speaking of would be force, not momentum. Force and momentum are inversely related, but it takes force to get an object to have momentum. And, as stated above, we don't know the rate of acceleration so we can't mathematically solve this problem.
Also, why the differentiation of "felt recoil" and not actual recoil? Do you think that they might differ? If you want to know which has the greater "felt recoil", then just simply perform a blind test. No, you don't need to shoot blindfolded though those that have seen me shoot think it couldn't hurt :)
Joel
[Remember: velocity and acceleration are just a simple integration (or differentiation) away.]
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kilowhiskey
- Posts: 34
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Re: Felt recoil, light vs heavy projectile
Waiting on an airplane, so unfortunately for you all I got some time to show some simplified calculations for the question at hand. I will avoid use of integrals or derivations from differential elements, as they are unnecessary and obnoxious.
If we accelerate a 150 grain projectile from 0 to 800 ft/s with constant acceleration (not quite true, but close enough in this case) the average velocity of the bullet in the barrel is 400 feet per second. To make the math easy, let’s assume a 6” barrel (instead of 5”), so we can say the projectile spends 1/800th of a second in the barrel. Make sense? Likewise the 120 grain round going from 0 to 1000 ft/s will spend 1/1000th of a second in the barrel.
Now acceleration is the change in velocity divided by the change in time (or dv/dt for engineers in the room). So for the 150 grain round, we have a change in velocity of 800 feet per second divided by a total time of 1/800th of a second or A =(800ft/s)/(1/800 S) = 640000ft/s**2.
Likewise acceleration for the 120 grain round is A =(1000 ft/s)/(1/1000 s) = 1000000ft/s**2.
Now, the average force during this period of acceleration is defined by the classic formula F=MA. To make this formula work in standard English units, we need to convert the bullet weight in grains to the equally arcane unit of mass known as the slug. Conversions we use in earth’s gravity are 7000 grains=1 lb, and 1 slug =32.2 lbs. So (150 grains)*(1 lb/7000grains)*(1slug/32.2lb)= 0.000665 slugs. Similarly, the 120 grain bullet has a mass of 0.000532 slugs.
So, using F=MA, the average force exerted by the 150 grain projectile is (0.000665 slug)*(64000 ft/s**2) which equals 426 slug-ft/s**2, or 426 pounds-force (lbf). Using same calculation, we get average force for the 120 grain round of (0.00532 slugs)*(1000000 ft/s**2) = 532 lbf. So, the average force for the 150 grain round going slower is only 80% of that for the 120 grain round.
Now, there is another item we want to look at called impulse, which in this case is the force multiplied by the span of time J=F*t. Alternatively, using mathematic sleight of hand, it can be expressed as J =mass*(velocity final)-mass*(initial velocity). Since we know the force, all we have to do is multiply by the time the force is applied. No matter how we calculate it, for the 150 grain bullet, the impulse is (426 lbf)*(1/800 s) = 0.532 lbf-s. Likewise for the 120 grain round the impulse is (532 lbf)*(1/1000 s) = 0.532 lbf-s. (I leave to the reader to convert to the proper SI unit of Newton-Seconds.)
I mentioned a couple sentences ago impulse can be expressed as J =mass*(velocity final)-mass*(initial velocity). Since the initial velocity is zero (0), we get J=mass*velocity, which corresponds to the “power factor” calculation of weight*velocity. So for the 150 grain bullet going 88 feet/second, J = (0.000665slug)*(800 ft/s) = 0.532 lbf-s; same answer we had before.
So, what this is saying is that the governing powers to be for shooting rapidly at large-ish targets have decided the critical factor for leveling the playing field is the total impulse the round subjects the competitor to. Also, what we’ve just shown is for a given impulse (or “power factor”), the bigger bullet gives a lower average force, but for a slightly longer period of time. But you knew that already.
In summation, despite long winded abuse of high school physics and basic math, I’ve added nothing of value to this discussion, and have inconvenienced more than a few electrons.
If we accelerate a 150 grain projectile from 0 to 800 ft/s with constant acceleration (not quite true, but close enough in this case) the average velocity of the bullet in the barrel is 400 feet per second. To make the math easy, let’s assume a 6” barrel (instead of 5”), so we can say the projectile spends 1/800th of a second in the barrel. Make sense? Likewise the 120 grain round going from 0 to 1000 ft/s will spend 1/1000th of a second in the barrel.
Now acceleration is the change in velocity divided by the change in time (or dv/dt for engineers in the room). So for the 150 grain round, we have a change in velocity of 800 feet per second divided by a total time of 1/800th of a second or A =(800ft/s)/(1/800 S) = 640000ft/s**2.
Likewise acceleration for the 120 grain round is A =(1000 ft/s)/(1/1000 s) = 1000000ft/s**2.
Now, the average force during this period of acceleration is defined by the classic formula F=MA. To make this formula work in standard English units, we need to convert the bullet weight in grains to the equally arcane unit of mass known as the slug. Conversions we use in earth’s gravity are 7000 grains=1 lb, and 1 slug =32.2 lbs. So (150 grains)*(1 lb/7000grains)*(1slug/32.2lb)= 0.000665 slugs. Similarly, the 120 grain bullet has a mass of 0.000532 slugs.
So, using F=MA, the average force exerted by the 150 grain projectile is (0.000665 slug)*(64000 ft/s**2) which equals 426 slug-ft/s**2, or 426 pounds-force (lbf). Using same calculation, we get average force for the 120 grain round of (0.00532 slugs)*(1000000 ft/s**2) = 532 lbf. So, the average force for the 150 grain round going slower is only 80% of that for the 120 grain round.
Now, there is another item we want to look at called impulse, which in this case is the force multiplied by the span of time J=F*t. Alternatively, using mathematic sleight of hand, it can be expressed as J =mass*(velocity final)-mass*(initial velocity). Since we know the force, all we have to do is multiply by the time the force is applied. No matter how we calculate it, for the 150 grain bullet, the impulse is (426 lbf)*(1/800 s) = 0.532 lbf-s. Likewise for the 120 grain round the impulse is (532 lbf)*(1/1000 s) = 0.532 lbf-s. (I leave to the reader to convert to the proper SI unit of Newton-Seconds.)
I mentioned a couple sentences ago impulse can be expressed as J =mass*(velocity final)-mass*(initial velocity). Since the initial velocity is zero (0), we get J=mass*velocity, which corresponds to the “power factor” calculation of weight*velocity. So for the 150 grain bullet going 88 feet/second, J = (0.000665slug)*(800 ft/s) = 0.532 lbf-s; same answer we had before.
So, what this is saying is that the governing powers to be for shooting rapidly at large-ish targets have decided the critical factor for leveling the playing field is the total impulse the round subjects the competitor to. Also, what we’ve just shown is for a given impulse (or “power factor”), the bigger bullet gives a lower average force, but for a slightly longer period of time. But you knew that already.
In summation, despite long winded abuse of high school physics and basic math, I’ve added nothing of value to this discussion, and have inconvenienced more than a few electrons.
Re: Felt recoil, light vs heavy projectile
Is this for a pistol competition.
Re: Felt recoil, light vs heavy projectile
Using simple Newtonian physics, the recoil will be the same, the momentum of the two bullets is the same (energy has nothing to do with it at this point), the impulse is the same, the recoil of the gun by itself will be exactly the same.
The total recoil reaction might be different, ignoring that the bullets in the magazine weigh differently, the hand-arm-body system is not a simple mass-spring, its a viscoelastic system so behaves differently depending on the profile of the impulse. So a short hard tap might not move the body as much as a slow gentle push.
Then there's perception of recoil. If its over quicker it might seem there's less of it. If the peak force is lower the 'recoil' might seem lower. A heavier gun seems to 'recoil' less, as it rises less and more slowly, and the peak force felt is lower, in fact the recoil is exactly the same as a lighter gun. The energy delivered to the body, and the rate of delivery might be relevant.
Its much harder to define perceived recoil than deal with equations.
Personally I've found light fast bullets to be better than slow heavy bullets for the same power factor in a revolver.
Its also less effort to turn the cylinder.
The total recoil reaction might be different, ignoring that the bullets in the magazine weigh differently, the hand-arm-body system is not a simple mass-spring, its a viscoelastic system so behaves differently depending on the profile of the impulse. So a short hard tap might not move the body as much as a slow gentle push.
Then there's perception of recoil. If its over quicker it might seem there's less of it. If the peak force is lower the 'recoil' might seem lower. A heavier gun seems to 'recoil' less, as it rises less and more slowly, and the peak force felt is lower, in fact the recoil is exactly the same as a lighter gun. The energy delivered to the body, and the rate of delivery might be relevant.
Its much harder to define perceived recoil than deal with equations.
Personally I've found light fast bullets to be better than slow heavy bullets for the same power factor in a revolver.
Its also less effort to turn the cylinder.
Re: Felt recoil, light vs heavy projectile
There is a lot of information from testing faster/slower burning powders and different bullet weights on 38super.net
Re: Felt recoil, light vs heavy projectile
We know that the momentums are the same but I think the key to the felt bit of
this is the powder charge.
To launch a lighter projectile faster in the same barrel length we need to accelerate
a lot faster and thus a lot more powder.
Typically you may need up to a grain more of the same powder.
Recoil is the reaction of both the projectile and the powder weight, and somewhere in all
this must come muzzle blast as the projectile exists the barrel.
Also if we change the powder burn rate we change both peak pressures and acceleration
rates as well as charge weight.
this is the powder charge.
To launch a lighter projectile faster in the same barrel length we need to accelerate
a lot faster and thus a lot more powder.
Typically you may need up to a grain more of the same powder.
Recoil is the reaction of both the projectile and the powder weight, and somewhere in all
this must come muzzle blast as the projectile exists the barrel.
Also if we change the powder burn rate we change both peak pressures and acceleration
rates as well as charge weight.
Re: Felt recoil, light vs heavy projectile
You'll just have to try it and see what "feels" better for you.
The thing is, there are so many variables (the shape of the grip, the material the grip is made of, bore axis, how heavy your arm is, your shooting posture, the alignment of your arm(s), the proportion of muscle and adipose tissue in your hand/arm/torso, and probably even auditory-tactile synesthesia that can make a louder gunshot cause you to perceive more recoil.
For example, part of the ongoing 9mm vs 45 debate is that some shooters report that a 9mm or 38 Super is more unpleasant to shoot than a "comparable" 45 load to them, even in comparable guns (like in a 1911) - are they wrong? Well, the original question is about "felt" recoil, so if they think they're feeling it...
Since we're talking about FELT recoil (and not the actual energy impulse) here's an extreme example:
3000 lb. car (that's roughly a Honda Civic with a driver) at 1 mph = 100.3 ft/lbs.
40 grain bullet (as in .22LR) at 1063 ft/sec (a typical target round velocity) = 100.3 ft/lbs.
Obviously those would be felt quite differently.
One other thing - I'm sure there's a lot of individual variation as well.
I'm a large(ish), strong(ish) man, and when I shoot handguns, recoil generally doesn't bother me, even with caliber/gun combinations that are often called unpleasant. However, when I shoot long guns the opposite seems to be true - I'm apparently more recoil-sensitive than most, whether with high velocity impulses (e.g. .30/06, .308) or slower ones (12 gauge). So, of course, YMMV. So like I said at the beginning, try out some of your possible combinations - anyway, that's a great excuse to shoot more!
The thing is, there are so many variables (the shape of the grip, the material the grip is made of, bore axis, how heavy your arm is, your shooting posture, the alignment of your arm(s), the proportion of muscle and adipose tissue in your hand/arm/torso, and probably even auditory-tactile synesthesia that can make a louder gunshot cause you to perceive more recoil.
For example, part of the ongoing 9mm vs 45 debate is that some shooters report that a 9mm or 38 Super is more unpleasant to shoot than a "comparable" 45 load to them, even in comparable guns (like in a 1911) - are they wrong? Well, the original question is about "felt" recoil, so if they think they're feeling it...
Since we're talking about FELT recoil (and not the actual energy impulse) here's an extreme example:
3000 lb. car (that's roughly a Honda Civic with a driver) at 1 mph = 100.3 ft/lbs.
40 grain bullet (as in .22LR) at 1063 ft/sec (a typical target round velocity) = 100.3 ft/lbs.
Obviously those would be felt quite differently.
One other thing - I'm sure there's a lot of individual variation as well.
I'm a large(ish), strong(ish) man, and when I shoot handguns, recoil generally doesn't bother me, even with caliber/gun combinations that are often called unpleasant. However, when I shoot long guns the opposite seems to be true - I'm apparently more recoil-sensitive than most, whether with high velocity impulses (e.g. .30/06, .308) or slower ones (12 gauge). So, of course, YMMV. So like I said at the beginning, try out some of your possible combinations - anyway, that's a great excuse to shoot more!