Questions about the irrelevance of energy (ft-lbs)

[HandgunHTR]

Yea I should have said rifle not shooter. The point was that the bullet receives more energy due to it having smaller mass.

No it doesn't. The energy is the exact same. The reason the bullet travels at a much higher speed is because of the smaller mass. If you could magically make a rifle have the same mass as the bullet, it would travel the same speed as the bullet, just in the opposite direction.

 

[BigCountry49]

No it doesn't. The energy is the exact same. The reason the bullet travels at a much higher speed is because of the smaller mass. If you could magically make a rifle weigh the same as the bullet, it would travel the same speed as the bullet, just in the opposite direction.

Wait, so you’re saying the rifle receives the same amount of energy as the bullet?

 

[waldo9190]

Wait, so you’re saying the rifle receives the same amount of energy as the bullet?

Well when you think about the fact that object A (bullet) weighs 150-ish grains, and object B (rifle) weighs 70,000-ish grains, its not so hard to fathom how one of them moves significantly faster than the other.

 

[Bluefish]

No it doesn't. The energy is the exact same. The reason the bullet travels at a much higher speed is because of the smaller mass. If you could magically make a rifle weigh the same as the bullet, it would travel the same speed as the bullet, just in the opposite direction.

I think energy is being substituted for momentum. The momentum is conserved, energy is calculated from the velocity of the objects in motion. Since the larger object moves more slowly, energy is significantly less due to the velocity being squared in energy and not in momentum. Energy = 1/2 x mass x velocity ^2, momentum = mass x velocity.

 

[Caseknife]

Wait, so you’re saying the rifle receives the same amount of energy as the bullet?

Newton's Third Law of Motion, for every action there is an equal and opposite reaction. So, yes, @HandgunHTR statement is correct . If the rifle weighed the same as the projectile and powder, wouldn't want to pull the trigger standing behind it.

 

[BigCountry49]

Newton's Third Law of Motion, for every action there is an equal and opposite reaction. So, yes, @HandgunHTR statement is correct . If the rifle weighed the same as the projectile and powder, wouldn't want to pull the trigger standing behind it.

Newton’s third law applies to force and momentum, not energy. The rifle will receive the same amount of momentum, but not the same energy as the bullet.

 

[Dobermann]

I just spend time with a sniper who was deployed 4 times in Iraq. They did shoot .338 L FMJ BT.

Did they say how much knockdown power it had?

 

[HandgunHTR]

I think energy is being substituted for momentum. The momentum is conserved, energy is calculated from the velocity of the objects in motion. Since the larger object moves more slowly, energy is significantly less due to the velocity being squared in energy and not in momentum. Energy = 1/2 x mass x velocity ^2, momentum = mass x velocity.

I am well aware of the differences between energy and momentum. This is ultimately why it is difficult having this conversation with people who's understanding of physics comes from gun rags and ammo boxes (comment not aimed at you, just folks on gun forums in general).

The statement that I refuted was "the bullet receives more energy due to it having a smaller mass". That is simply not correct. Accuracy of wording is crucial when having these discussions, because as you have pointed out, there is a significant difference between energy, momentum, mass, weight, etc.

The amount of KE imparted to the bullet and the rifle are the same. However, in order to overcome inertia a lot more of it is used up to convert that energy to motion when talking about the rifle. So the amount of acceleration for the bullet is much higher than it is for the rifle (Newton's 2nd law). The result of this is that the bullet ends up with more momentum than the rifle, but energy imparted to both of those objects is the same.

 

[Stinky Coyote]

and the bullet is only in the tube for a nano second, taking all it's work potential (energy) with it, rifle quits moving pretty quick, why recoil numbers are what they are, a tiny portion of the 62,000 psi explosion goes to the shoulder

 

[Stinky Coyote]

now we take that 62,000 psi and lose some down the tube, some into the shooter, then more through the air, then it arrives at target and whatever is left we translate to ft/lbs although it does provoke some additional thought to the 'energy' at terminal end, ie; if looked at in psi may be easier to visualize than ft/lbs, psi blowing chunks of fragmenting bullets outward in right distance in animal, psi released an easier visual to outward expansion of energy than say ft/lbs,

if you know an eldm of same weight and impact velocity as a mono and the m goes half as deep and weighs half as much as the copper, it has in that distance done twice the 'work', psi or ft/lbs, fragments being driven outward by this 'energy' damaging a lot more material over shorter distance and correspondingly more drt's

edit addition; is there 30,000 psi of the original 62,000 left at a given impact velocity and does that release over 16" or 32", or is ft/lbs the better energy unit as it accounts for bullet mass, can remaining psi be part of that or back calculated from ft/lbs at the terminal end?

and this what we do, we don't need to know more than what we know, get enough sd, construction, and impact velocity for game intended and preference to speed of kill and we're good to go

as Mac said, until we can measure work in gel to be able to start computing a terminal coefficient we're stuck working it all out like the past 38 pages, not the end of the world but we're also not done, it's a lot easier understanding what .523 bc does differently than .697 bc in how we choose to our desires, the TC would do the same thing to choosing for our desires as we'd understand what performance level we're after for an intended goal, we would see the picture between an eldm TC vs a mono TC and this ability would change the game in how we discuss this stuff and assist all shooters of live targets around the world for any size game etc.

till then, eldm construction type, .25 sd or higher, 1800 fps.....and that covers off about the peak of NA big game for those that prefer to walk right up to everything after they shoot, energy does not need to be relevant although it's there and would be part of the equations likely to get to the TC

in meantime we can look at an eldm in gel and if they give impact, final bullet weight/diameter and inches of penetration we can math that somewhat to get a better visualization of how that mono will damage internals vs an eldm on a 'per inch' basis, little eldm vs big eldm lower ft/lbs per inch, higher ft/lbs per inch, both kill quickly but there's still a difference and work potential that may or may not be relevant to most goals, the mono's transfer easily explainable by going twice as deep with half the ft/lbs per inch along the way, where needing more penetration than normal broadside this becomes important and all the way up to dg where you want all the energy applied to penetration and use solids so that can be achieved, the TC would just make talking about all this an equivalent to discussing BC on the inflight side....easy and fast, much better than say cup/core or match vs bonded or mono....get it in objective number and all the noise goes away

 

[5811]

The amount of KE imparted to the bullet and the rifle are the same. However, in order to overcome inertia a lot more of it is used up to convert that energy to motion when talking about the rifle. So the amount of acceleration for the bullet is much higher than it is for the rifle (Newton's 2nd law). The result of this is that the bullet ends up with more momentum than the rifle, but energy imparted to both of those objects is the same.

The same math can be carried to the animal vs the bullet, which is why the animal is pushed a minimal distance by the bullet, i.e., it barely moves as a result of the bullets energy, aside from a physiological response. Knockdown power is a misnomer.

 

[AZ_Hunter]

Newton's Third Law of Motion, for every action there is an equal and opposite reaction. So, yes, @HandgunHTR statement is correct . If the rifle weighed the same as the projectile and powder, wouldn't want to pull the trigger standing behind it.

Or if shot in a 0 G vacuum…. That would be fun ride. Take the 30-06 to space and fire a round then accelerate backwards at the same speed of the bullet going forwards. Yeee haw!

 

[HandgunHTR]

now we take that 62,000 psi and lose some down the tube, some into the shooter, then more through the air, then it arrives at target and whatever is left we translate to ft/lbs although it does provoke some additional thought to the 'energy' at terminal end, ie; if looked at in psi may be easier to visualize than ft/lbs, psi blowing chunks of fragmenting bullets outward in right distance in animal, psi released an easier visual to outward expansion of energy than say ft/lbs,

if you know an eldm of same weight and impact velocity as a mono and the m goes half as deep and weighs half as much as the copper, it has in that distance done twice the 'work', psi or ft/lbs, fragments being driven outward by this 'energy' damaging a lot more material over shorter distance and correspondingly more drt's

edit addition; is there 30,000 psi of the original 62,000 left at a given impact velocity and does that release over 16" or 32", or is ft/lbs the better energy unit as it accounts for bullet mass, can remaining psi be part of that or back calculated from ft/lbs at the terminal end?

and this what we do, we don't need to know more than what we know, get enough sd, construction, and impact velocity for game intended and preference to speed of kill and we're good to go

as Mac said, until we can measure work in gel to be able to start computing a terminal coefficient we're stuck working it all out like the past 38 pages, not the end of the world but we're also not done, it's a lot easier understanding what .523 bc does differently than .697 bc in how we choose to our desires, the TC would do the same thing to choosing for our desires as we'd understand what performance level we're after for an intended goal, we would see the picture between an eldm TC vs a mono TC and this ability would change the game in how we discuss this stuff and assist all shooters of live targets around the world for any size game etc.

till then, eldm construction type, .25 sd or higher, 1800 fps.....and that covers off about the peak of NA big game for those that prefer to walk right up to everything after they shoot, energy does not need to be relevant although it's there and would be part of the equations likely to get to the TC

in meantime we can look at an eldm in gel and if they give impact, final bullet weight/diameter and inches of penetration we can math that somewhat to get a better visualization of how that mono will damage internals vs an eldm on a 'per inch' basis, little eldm vs big eldm lower ft/lbs per inch, higher ft/lbs per inch, both kill quickly but there's still a difference and work potential that may or may not be relevant to most goals, the mono's transfer easily explainable by going twice as deep with half the ft/lbs per inch along the way, where needing more penetration than normal broadside this becomes important and all the way up to dg where you want all the energy applied to penetration and use solids so that can be achieved, the TC would just make talking about all this an equivalent to discussing BC on the inflight side....easy and fast, much better than say cup/core or match vs bonded or mono....get it in objective number and all the noise goes away

Please, just stop. Your complete misunderstanding of what PSI is and how it is applied is just muddying the water even more.

Your continued assertion that a "work curve" can be developed for a given bullet continues to have more holes in it than Form's evaluation targets as there are so many variables that you cannot account for that it is not even remotely feasible. That is why practical tests are carried out and educated observations are made based on them. Each animal is different, each hit is different, and each bullet will behave differently based on those variables.