[norahc]

I've been thinking about this for a while, and wanted your opinions on if I'm on the right track or not.

Most of us are aware of the current metrics used to measure the effectiveness of bullets, but for those that aren't here's a quick review and some definitions.

Acceleration = change in velocity / change in time
Velocity = speed of bullet travel
Mass = weight of bullet
Kinetic energy = 1/2 * m * v2 = This is commonly referred to as muzzle energy in firearms

Some people advocate for a faster bullet, because velocity (being squared) has a bigger effect on energy than the mass does. Theoretically, this is correct. However, in the real world, it is often misleading.

Force = Mass * acceleration
In a firearms application, Force may be a more appropriate measure of effectiveness because it is an indication of how much of it is transferred to the target. The Acceleration in the formula is provided by the bullet's deceleration in it's target, or how much velocity it loses. So a bullet travelling at 3000 fps that passes through the target and emerges from the other side at 3000 fps applies no Force to the target. A bullet that stops in the target has transferred all of it's Force into the target medium, and a bullet that exits at a lower velocity has transferred some of it's energy to the target.

So my question is, given a calibrated medium such as ballistics gel, wouldn't Force be a more accurate indicator of the mythical stopping power?

The application of Force over a fixed distance is the formula for Work
Work = Force * Distance.
If we standardize a distance of let's say 12", we could come up with an indicator of how much work a bullet would do in a target. The advantage of using Work, or even Force, as an indicator of a bullet's effectiveness is that it tells us how much of that Kinetic Energy that is available is actually transferred to a calibrated target such as ballistics gelatin.

 

[68c15]

so, in essence the hand needs to transfer as much energy as possible to the side of the liberal's head to wake them up and see the truth?

 

[RunningOnMT]

You're pretty much on target with your analysis, that's why I and many others prefer the .45 acp.

Just a miner correction to your definitions. Velocity is speed when a specific direction is given.

 

[Slabsides]

Thats great when comparing simple physics on solid objects. Shooting things like cans, steel plates or other solid objects. When it comes to defensive shooting, you must add a whole different realm into the mix: Fluid dynamics. Where does temporary stretch cavity factor into the above equations?

This is where things change dramatically. Velocity factors in heavily in fluids. Drop a softball from 1 foot into a kiddie pool. Now drop a baseball from 1000 feet into the same pool. Which one displaces and upsets the most fluid? The softball is obviously larger but does far less because of lower velocity.

A good equation to the firearms world is to compare the actual damage done to a living thing filled with blood and tissue between a 230gr .45 moving at 950fps and a tiny 55gr .223 moving at 3200fps.

For shooting engine blocks, I'll take something big and slow. For defense against a living thing, I'll take something small and fast. (big AND fast is best, but I cannot carry a 30mm chain gun very easily....but it would be cool as hell, wouldn't it?)

 

[myfriendis410]

If you change "force" into "momentum" you are back where the big debate took place between Elmer Keith (momentum) and Jack O'Connor (Kinetic energy). There have been arguments and debates about the relative merits of the two since Hacker's book came out (an interesting read) in the early 1900's.

Anybody who has shot bowling pins in competition rapidly becomes a fan of momentum in a handgun, but when you start discussing rifle you enter a whole different quantum of energy that makes it impossible IMO to compare handgun and rifle.

 

[bluesea112]

Norahc, I just started a thread regarding the same issue when comparing a 150gr projectile to a 175gr projectile. In the particular caliber, the 150gr bullet is superior in every aspect: Less drop, more energy, and less recoil. My question was would anybody load a 175gr projectile when the numbers show that a 150gr bullet is far superior in every catagory: velocity, trajectory, and energy

 

[JLA]

Trust me charles it only looks good on paper. If you could only ever shoot your gun in a vacuum the 150 would indeed outperform. But when atmospheric conditions get ahold of the projectile the heavier bullet, often having a higher BC will outperform downrange.