Home Forums Hunting & Shooting General Big Game Bullet weight??

Velocity and acceleration are two different concepts. There is no mention of acceleration in the formula for energy, only mass and velocity (E = 1/2*m*v*v). Acceleration measures a change in velocity over time. (v1-v2 / t1-t2)

A projectiles KE at any point in time does not depend on its acceleration, which requires multiple points in time. When smokingrope adds a specific mass (or range of masses) to his calculations and the maximum destructive capability of a bullet at a specific velocity, he is considering KE, not velocity alone and not force.



You get it exactly, and that is what I've been saying consistently.

A bullet's energy determines its MAXIMUM destructive capability, not the ACTUAL destruction it will do. The ACTUAL destruction depends on many other factors including bullet construction and types and amount of target material encountered.

A projectile's velocity, considered alone, tells you nothing about its destructive capability. You have to consider mass as well, which is exactly what smokinrope does when he says that at 1800fps he would choose a bullet somewhere between a 60g and 500g partition for elk. If bullet mass didn't matter the1800fps 60g Partition would be equally effective on elk.

Although the 60g and 500g Partitions have the same "Optimum Performance" velocity (1800fps minimum to unlimited), there is a reason Nosler does not include the 60g Partition in their recommendations for elk sized game.

Like I have been saying it is Energy that has a tighter measurement of the 308 class cartridge.

If the ordinances are sorted for acceptable sectional density....

There is less difference between the rounds in energy than velocity.

KE is how a non explosive projectiles harvests game.

Without the proper KE the ordinance won't open and do its deal.

Unless it is an arrow.

But then kinetic energy is measured in marketing archery equipment also.

So go figure.

if I calculate [velocity and mass] I am working out the 'momentum' (p) value.

If I calculate [acceleration and mass] I am working out the 'Force' value.

with momentum being dependent on the force acting on it.

with that, Does anyone then really need to apply an energy formula for hunting bullets?

I like Ray Wiley Hubbard. I've seen him several times.

Momentum and energy are two very different but related (by mass and velocity) concepts.

Given two objects with equal momentum but a 10x difference in mass, which object will have the higher energy (and therefore destructive capability) level?

The correct answer is is that the lighter (by a factor of 10) object will have a velocity 10x greater to achieve the same momentum value and therefore 100 times more energy and destructive capability than the heavier object.

Momentum = m*v

Energy= 1/2*m*v*v


Assume the following for two objects with equal momentum:

Object 1: mass of 1, velocity of 10, momentum = 10
Object 2: mass of 10, velocity of 1, momentum = 10


For those objects:

Object 1 energy = 1/2*1*10*10 = 50
Object 2 energy = 1/2*10*1*1 = 5


Momentum considered alone does not directly relate to a projectile's ability to do work, whereas its energy level does.




It is true that Force = mass * acceleration. But force also tells you nothing about a projectile's ability to do work at a given velocity. The formula for acceleration is:
a=(v1-v2)/(t1-t2)

At any given velocity (1800fps in the example I used with smokinrope), there is no acceleration because v1=v2. Thus:

v1 = v2
v1-v2 = v1-v1

t1-t2 = x

a = (v1-v1)/x = 0/x = 0

f = m*a = m*0 = 0

Therefore, at any given velocity, force = 0, which, like velocity alone, tells you nothing about a projectile's destructive capability.

Mass does not have direction.

Don't know a whole lot about mass vs direction, etc, etc, etc. But I do know I killed an 800 pound 7X6 bull elk yesterday with a 100 grain slick trick, delivered from 23 meters from a Hoyt Defiant Turbo.

Nice Pat! You do any energy calculations to make sure it would die first? Grin....

Congrats on the elk. Did the arrow over penetrate?

I was just keeping tabs on a poster with a tenuous grasp (at best) of physics as evidenced by the boners repeatedly dropped in his discussion of the subject. I'm not about to tell you anything about hunting.

I know, it's all good! I think we all need to just go hunt....sort out all the details later!

Nasty little bastard...

Regarding penetration, my dad always says that a guy at the bottom of a pool might be safe from a bullet from a hunting rifle, but he's likely in trouble if there's an arrow coming at just a tenth of the speed.

Oh yeah!

Good question, and Pat, did you get a pass through? Looks like your pet broadhead failed to expand due to schittty kinetic energy.

my understanding In the case of bullet momentum (mass in motion) it does.

Motion can be decscribed in terms of displacement, distance, velocity, acceleration, time and speed.

Go back to school. Mass is independent of direction just as it is independent of gravity.

Speed is a scalar quantity with no direction.
Velocity is a vector quantity which has both magnitude and direction.

Any object with mass that also has velocity has momentum. It has direction because it has velocity, not because it has mass.

Mass has no direction.

mass no direction, ok got it.

If I calculate [acceleration and mass] I am working out the 'Force' value.
(which results in Newtons and can be converted to ft/lb) 1 Newton = 0.737562149 ft/lb

with that, Does anyone then really need to apply an energy formula for hunting bullets?

Again, go back to school.

Ft-lbs convert to newton-meters, not newtons.

Newtons are a measurement of force. Newton-meters and ft-lbs are a measure of energy.

bumber!...