Effective velocity

[bobcat]

Foot pounds of energy is just a calculated number, personally I don't pay much attention to it. If you have the velocity needed, and the right bullet, that's all that matters.

[7mmfan]

Velocity provides the oompf for expansion which in turn results in energy into the target. Like mentioned, its a dance between velocity, expansion aka bullet performance, and the resulting trasfer of energy. I find it fascinating.

I'm with ya on finding it fascinating.  I don't even have a long-range setup (nor the necessary skills to think about shooting past 350 or so) but I'm so much of a nerd I still like to learn about it (cf. the thread on the Coriolis effect in virtual campfire  ).

There's no way to untangle velocity from energy -- it's not as if mass changes for a bullet in flight, so velocity is really the only variable in external ballistics anyway.  But it's literally energy that makes the bullet deform/expand so you think that would be the baseline metric that's used.  But apparently velocity is more handy?   

EDIT: Energy is not what makes the bullet expand, velocity and target resistence is. The velocity the bullet is traveling at, and the density of the target the bullet hits are what determine the amount of energy that is transferred at impact.

Consider this. I'm using fabricated numbers on the fly, these have no real life bearing on anything, just an example. A bullet is traveling at 2500 fps, and at the speed, carries a 2000 FP of energy. If, when the bullet hits it's intended target, it expands, plows through the target, and is found just under the skin on the far side. The bullet expended all 2000 FP of its retained energy given its velocity.

However, take the the same speed/energy, but the bullet design doesn't allow for full expansion at that speed. When this bullet hits the intended target, it zips through and disappears over the horizon. How much energy did it release on its target? 50% of it? 25% of it?

It's a lot of calculus and algebra and cosigns, and other stuff that I haven't played with in a long time, but the end result is, energy is a direct result of mass x velocity, and transferred energy is a direct result of bullet design and how much of the energy it expends on its target.

My understanding is that energy is a product of mass (weight) x velocity. The lower the velocity, the lower the energy. Take a 180 gr accubond and throw it as hard as you can at thing, its not going to expand or deform other than superficially. Fire it at 2000 fps, and it penetrates/expands, and destroys. The mass of the bullet needs to be traveling at a minimum velocity to perform.

What the minimum velocity is seems to be up for debate, but 1800 fps depending on the bullet design, seems to be the benchmark.

[yakimanoob]

My understanding is that energy is a product of mass (weight) x velocity. The lower the velocity, the lower the energy. Take a 180 gr accubond and throw it as hard as you can at thing, its not going to expand or deform other than superficially. Fire it at 2000 fps, and it penetrates/expands, and destroys. The mass of the bullet needs to be traveling at a minimum velocity to perform.

That's the gist of it. 

Technically (kinetic) energy is half the product of the mass and the square of the velocity, so small changes in velocity have a much larger effect on the energy than small changes in mass.  Mass times velocity is the quantity we call momentum and is a slightly different idea. 

The oddity for me in using velocity over energy is that if you know one (and the mass of the bullet, which you always should) then you know the other.  E = 0.5*m*(v^2).  Or, v = sqrt(2E/m).  It must be that velocity is just a more convenient metric because maybe an 85gr bullet with 2000 ft-lbs of energy expands much differently than a 180gr bullet with the same energy, but they expand similarly if they're both moving at 1800 fps.   

[7mmfan]

My understanding is that energy is a product of mass (weight) x velocity. The lower the velocity, the lower the energy. Take a 180 gr accubond and throw it as hard as you can at thing, its not going to expand or deform other than superficially. Fire it at 2000 fps, and it penetrates/expands, and destroys. The mass of the bullet needs to be traveling at a minimum velocity to perform.

That's the gist of it. 

Technically (kinetic) energy is half the product of the mass and the square of the velocity, so small changes in velocity have a much larger effect on the energy than small changes in mass.  Mass times velocity is the quantity we call momentum and is a slightly different idea. 

The oddity for me in using velocity over energy is that if you know one (and the mass of the bullet, which you always should) then you know the other.  E = 0.5*m*(v^2).  Or, v = sqrt(2E/m).  It must be that velocity is just a more convenient metric because maybe an 85gr bullet with 2000 ft-lbs of energy expands much differently than a 180gr bullet with the same energy, but they expand similarly if they're both moving at 1800 fps.   

That equation tipped me over. I have baby brain, and lack of sleep and only 4 cups of coffee today. I'm bowing out. Carry on. 

[yakimanoob]

EDIT: Energy is not what makes the bullet expand, velocity and target resistence is. The velocity the bullet is traveling at, and the density of the target the bullet hits are what determine the amount of energy that is transferred at impact.

Consider this. I'm using fabricated numbers on the fly, these have no real life bearing on anything, just an example. A bullet is traveling at 2500 fps, and at the speed, carries a 2000 FP of energy. If, when the bullet hits it's intended target, it expands, plows through the target, and is found just under the skin on the far side. The bullet expended all 2000 FP of its retained energy given its velocity.

However, take the the same speed/energy, but the bullet design doesn't allow for full expansion at that speed. When this bullet hits the intended target, it zips through and disappears over the horizon. How much energy did it release on its target? 50% of it? 25% of it?

It's a lot of calculus and algebra and cosigns, and other stuff that I haven't played with in a long time, but the end result is, energy is a direct result of mass x velocity, and transferred energy is a direct result of bullet design and how much of the energy it expends on its target.

My understanding is that energy is a product of mass (weight) x velocity. The lower the velocity, the lower the energy. Take a 180 gr accubond and throw it as hard as you can at thing, its not going to expand or deform other than superficially. Fire it at 2000 fps, and it penetrates/expands, and destroys. The mass of the bullet needs to be traveling at a minimum velocity to perform.

What the minimum velocity is seems to be up for debate, but 1800 fps depending on the bullet design, seems to be the benchmark.

I agree with the concepts you're getting at, just not the technicalities.  It is only energy that makes the bullet expand, but I should have clarified that there are more types of energy than the kinetic energy measured in ft-lbs that we normally talk about.  Technically it's mechanical energy between the target and the bullet that causes the bullet to deform -- the target is literally pushing the bullet into that shape.  This mechanical energy ultimately comes from the kinetic energy of the bullet in flight of course, but like you said there's a LOT going on when it comes to terminal ballistics, and it doesn't necessarily make sense to measure the mechanical energy that deforms the bullet in terms of the kinetic energy it has right before impact. 

[yakimanoob]

That equation tipped me over. I have baby brain, and lack of sleep and only 4 cups of coffee today. I'm bowing out. Carry on. 

Haha, yeah I should leave the physics for another time and place.  Sorry to side-track your thread, Baker! 

[Bob33]

Velocity provides the oompf for expansion which in turn results in energy into the target. Like mentioned, its a dance between velocity, expansion aka bullet performance, and the resulting trasfer of energy. I find it fascinating.

I'm with ya on finding it fascinating.  I don't even have a long-range setup (nor the necessary skills to think about shooting past 350 or so) but I'm so much of a nerd I still like to learn about it (cf. the thread on the Coriolis effect in virtual campfire  ).

There's no way to untangle velocity from energy -- it's not as if mass changes for a bullet in flight, so velocity is really the only variable in external ballistics anyway.  But it's literally energy that makes the bullet deform/expand so you think that would be the baseline metric that's used.  But apparently velocity is more handy?   

EDIT: Energy is not what makes the bullet expand, velocity and target resistence is. The velocity the bullet is traveling at, and the density of the target the bullet hits are what determine the amount of energy that is transferred at impact.

Consider this. I'm using fabricated numbers on the fly, these have no real life bearing on anything, just an example. A bullet is traveling at 2500 fps, and at the speed, carries a 2000 FP of energy. If, when the bullet hits it's intended target, it expands, plows through the target, and is found just under the skin on the far side. The bullet expended all 2000 FP of its retained energy given its velocity.

However, take the the same speed/energy, but the bullet design doesn't allow for full expansion at that speed. When this bullet hits the intended target, it zips through and disappears over the horizon. How much energy did it release on its target? 50% of it? 25% of it?

It's a lot of calculus and algebra and cosigns, and other stuff that I haven't played with in a long time, but the end result is, energy is a direct result of mass x velocity, and transferred energy is a direct result of bullet design and how much of the energy it expends on its target.

My understanding is that energy is a product of mass (weight) x velocity. The lower the velocity, the lower the energy. Take a 180 gr accubond and throw it as hard as you can at thing, its not going to expand or deform other than superficially. Fire it at 2000 fps, and it penetrates/expands, and destroys. The mass of the bullet needs to be traveling at a minimum velocity to perform.

What the minimum velocity is seems to be up for debate, but 1800 fps depending on the bullet design, seems to be the benchmark.

That information is essentially accurate but misses a few key points.

First, a bullet that lodges on the far side and doesn't exit is much less likely to leave a blood trail for tracking.

Secondly, the issues of wound channel size, bullet cavitation, and hydrostatic shock also play roles in how quickly an animal dies.

A simple formula for the kinetic energy of a bullet is ( bullet_grains x velocity x velocity ) / 450,800.

Example of a 180 grain bullet at 2700 ft/second: (180 x 2700 x 2700) / 450800 = 2910 foot pounds of energy.

[yakimanoob]

A simple formula for the kinetic energy of a bullet is ( bullet_grains x velocity x velocity ) / 450,800.

Example of a 180 grain bullet at 2700 ft/second: (180 x 2700 x 2700) / 450800 = 2910 foot pounds of energy.

I just tried to figure out how this was the same as E = 1/2 m v^2 and got hit in the face by how incredibly *&$%ing stupid the imperial system is. 

7000 grains = 1 lb(mass) = 32.2fps*1lb(force).  Kinetic energy is measured in ft*lbs(force).  So if you start with grains, you have to divide by 7000*32.2, which is 225,400.  Once you apply the 1/2 part of the kinetic energy equation, you get the 450,800 in Bob's equation. 

OR if we measured everything in metric, there would be no conversions to do at all.  Mass of the bullet in grams, velocity in meters per second, plug into the equation and we're done.  F&^%ing British units 

[kselkhunter]

And the Brits don't even use the imperial systems anymore. The US, Myanmar, and Liberia are the last ones still using it. 

To the Op:  Find out what the minimum impact velocity is for your chosen bullet from the manufacturer and how it performs at varying velocities (some manufacturers supply photos of recovered bullets at various velocities).  And test them out at those ranges (Yorketransport did some good reviews on bullet performance).  A low velocity impact that pencils through will still kill an animal if it hits the heart/nervous system....but that shot at long ranges in hunting conditions can challenge even the most experienced long range shooters.

I've witnessed wannabe long range shooters lobbing bullets at a bull over a half a mile away and missed so badly they killed the calf standing next to it.        Not factoring how far wind can drift their bullet at those ranges. 

A 168gr ABLR out of my 7mmRM will have over 1800fps of velocity at 800 yards and thus the bullet will perform and my custom ballistic turrets take the guesswork out of bullet drop calculations.....but if that bullet encounters a 10mph cross wind halfway across the canyon it will drift multiple feet.  Lower BC bullets out of other calibers can drift 4 ft or more at those ranges.   I'm not skilled enough to make those wind estimations, so don't take such shots myself.

But, there are plenty of guys on this forum that can make a long range shot and have the gun, caliber, bullet, and years of experience and regular practice range time to pull it off every time.  They can give much better advice than I.  But, I'd expect a bigger 338 caliber variant would give the best of all worlds in velocity and higher BCs to better resist wind drift at longer ranges, as long as bullet stability (ie twist rate vs. bullet selection, etc.) is also factored in.