Terminal Ballistics from the Morgue

[Rod Snell]

Since BCs are the same - I guess the answer is never.

Just a comment from the ol' physics prof:

Even assuming the two bullets lose speed at the same rate (they won't, sectional density is different),
that does NOT mean KE will decrease at the same rate because KE is proportional to the SQUARE of velocity. A bullet that loses half its speed loses 3/4 of the KE.

Unfortunately, the drag on a projectile is also proportional to the SQUARE of speed, so the faster bullet slows down % higher than the one that starts slower. Look at a ballistics table for .270 rifle, for example, and while a 100gr bullet starts much faster, at distance, the 140gr bullet is going faster then the 100 gr and has much more energy.
At 25 feet, the relative loss is much smaller, but easily calculated from a ballistics chart.

The other problem is tht the effect of a bullet on tissue is not solely determined by the KE of the projectile, but is heavily influenced by the frontal area and sectional density. Of course, the trump card is where the bullet hits.

PS: The reason the numbers in the KE calculaions above look so large is the M stands for MASS, and the English unit of mass is the SLUG (approx 32#)

This handy calculator takes care of the units conversion for you:
http://www.handloads.com/calc/quick.asp

 

[SMS]

If we postulate that the purpose of shooting someone is to stop them from fighting or agressing against us...I for one would love to see how many assaults ended but did not kill the badguy with .380 or 9mm now those would be some good statistics...

Good point, only looking at morgue cases doesn't prove effectiveness in stopping an attack because you don't have to put someone in the morgue to stop an attack.

Of course it can be argued that the only foolproof way to stop the attack is to kill the attacker, but I'd be fine with leaving them sh$tting in a bag the rest of their lives as long as they stopped doing whatever it was that required me to shoot them.

 

[MoBoost]

Just a comment from the ol' physics prof:

Even assuming the two bullets lose speed at the same rate (they won't, sectional density is different),
that does NOT mean KE will decrease at the same rate because KE is proportional to the SQUARE of velocity. A bullet that loses half its speed loses 3/4 of the KE.

Unfortunately, the drag on a projectile is also proportional to the SQUARE of speed, so the faster bullet slows down % higher than the one that starts slower. Look at a ballistics table for .270 rifle, for example, and while a 100gr bullet starts much faster, at distance, the 140gr bullet is going faster then the 100 gr and has much more energy.
At 25 feet, the relative loss is much smaller, but easily calculated from a ballistics chart.

Oh, wow, that make perfect sense! I did some number crunching and indeed two energy curves cross at 40 yards (meaning 45 has more Kinetic energy from there on). Thanks for your correction.

The other problem is tht the effect of a bullet on tissue is not solely determined by the KE of the projectile, but is heavily influenced by the frontal area and sectional density. Of course, the trump card is where the bullet hits.

I yet to see any proof that "slightly more damage" from larger bullet makes any difference in a shot that didn't hit the "kill switch".

A lot of fights will end with a simple "hit" - leg, arm, abdomen - just a hit is enough.
In the cases where attacker is determined - double lung, heart, liver, etc - even those shots will not make him/her immediately stop. Only brain/spine will. And again in those cases I don't see how the size of the wound channel affects the outcome: heart is hit is a heart hit, collapsed lung is collapsed lung, etc.

 

[MoBoost]

Good point, only looking at morgue cases doesn't prove effectiveness in stopping an attack because you don't have to put someone in the morgue to stop an attack.

Of course it can be argued that the only foolproof way to stop the attack is to kill the attacker, but I'd be fine with leaving them sh$tting in a bag the rest of their lives as long as they stopped doing whatever it was that required me to shoot them.

+100!!!

Nor the fact that the guy ended up in the morgue means that the attack immediately stopped.

 

[NikatKimber]

While I agree with practically everything you said this quote was taken out of context. He was saying that in handguns you largely give up the advantage of velocity. In a handgun the 9mm is traveling faster yes, but is it fast enough to overcome practically doubling the weight? If the guy wasn't an ME, and was an engineer like me he could tell you using...wait for it....wait for it...MATHEMATICS!!!


KE=Kinetic Energy
KE=(1/2)M X V ^2 (^2 means squared)

.45 ACP using 230 gr and 890 FPS Velocity as pulled from ableammo.com for Speer Gold Dot

KE=.5 230 gr X 890 FPS ^2

.5 X 230 = 115

890 X 890 = 792,100

KE = 792,100 x 115

KE=91,091,500 units (whatever they are)

9MM Using 124 gr and 1150 FPS as pulled from ableammo.com for Speer Gold Dot

KE=.5 x 124 x 1150^2

KE=112 X 1,322,500

KE=148,120,000 units (whatever they are)

You can see the 9mm actually wins there by a large margin and I have some bad news, that calculation is done with the shortbarrel numbers for the 9mm. The regular 9mm is 1220 FPS, you do the math, its late and I don't wanna. So while I too carry the .45ACP as my choice the 9mm actually has more energy. Granted these are at the muzzle. The .45 will lose a smaller percentage of its energy at 25 feet than 9mm will, but the 9mm having such a large advantage to start with I don't see it being being diminished past that of the .45. Now there's an interesting piece of information to calculate, at what distance does the energy of the .45 surpass the 9mm? Then you will know at what distance you should switch sidearms from your .45 on your hip to your .357 tucked into your boot.

I shoot the .45 because I prefer its recoil characteristic of a push over the snap of the smaller calibers. Has little to do with the ballistics, but the .45 ACP is still more than adequate and knowing that I chose it for the preference listed above.

I knew something was off, so I ran through your calculations... You didn't divide 124/2 correctly, should be 62, not 112.

 

[ripnbst]

Just a comment from the ol' physics prof:

Even assuming the two bullets lose speed at the same rate (they won't, sectional density is different),
that does NOT mean KE will decrease at the same rate because KE is proportional to the SQUARE of velocity. A bullet that loses half its speed loses 3/4 of the KE.

Unfortunately, the drag on a projectile is also proportional to the SQUARE of speed, so the faster bullet slows down % higher than the one that starts slower. Look at a ballistics table for .270 rifle, for example, and while a 100gr bullet starts much faster, at distance, the 140gr bullet is going faster then the 100 gr and has much more energy.
At 25 feet, the relative loss is much smaller, but easily calculated from a ballistics chart.

The other problem is tht the effect of a bullet on tissue is not solely determined by the KE of the projectile, but is heavily influenced by the frontal area and sectional density. Of course, the trump card is where the bullet hits.

PS: The reason the numbers in the KE calculaions above look so large is the M stands for MASS, and the English unit of mass is the SLUG (approx 32#)

This handy calculator takes care of the units conversion for you:
http://www.handloads.com/calc/quick.asp

Oh, wow, that make perfect sense! I did some number crunching and indeed two energy curves cross at 40 yards (meaning 45 has more Kinetic energy from there on). Thanks for your correction.

So there you have it, engage targets beyond 40 yards with a .45 J/k, that might be tough to defend in court. But the math used above is the same as how people can say that something hotter freezes faster than if you put something in the freezer at room temperature. It doesn't actually take less time to freeze but it cools at a much greater rate if that makes sense.

 

[ripnbst]

You are right, it was late. I guess I was thinking 224 since the .45 was a 2XX number also. Good Catch, will go EDIT.

I knew something was off, so I ran through your calculations... You didn't divide 124/2 correctly, should be 62, not 112.

 

[NikatKimber]

You are right, it was late. I guess I was thinking 224 since the .45 was a 2XX number also. Good Catch, will go EDIT.

Ran more calculations.

......................9mm.......45 ACP
Diameter (in):..0.355........0.45
Weight (grns):...124..........230
MV (fps):.........1110..........850
Frt Area (in2):..0.099.......0.159....π*(Dia/2)^2
Mass (Slugs):..0.00055...0.00102...Unit Conversion, Weight in grains / 7000 (grns/lb) / 32.1 (lbs/slug)
ME (Ft Lbs):.....340.0.......369.8.....1/2 * Mass * Vel^2
Inertia ():.........0.61.........0.87....Mass * Vel
Drag Factor:...147322......125978...Frontal Area * Vel^2
......................1.06......................9mm Will slow this much faster *initially* than .45, given similar drag coefficients. This factor changes dynamically with speed, so as it slows down, the difference in the rate of acceleration changes (in this case, the difference decreases)

At the muzzle, a .45 has 8% more Kinetic energy, and 30% higher inertia. At 100yds, the .45 has 19% higher KE, and 34% higher inertia.

The numbers don't lie, the .45 ACP is a more powerful round. But as has been asked, is it enough to matter.

Don't get me wrong, I carry a 9mm. I have decided that for me, I prefer having 16 rounds of 9mm at a slight cost to me in power, to save on recoil and practice cost.

 

[MoBoost]

Ran more calculations.

......................9mm.......45 ACP
Diameter (in):..0.355........0.45
Weight (grns):...124..........230
MV (fps):.........1110..........850

Now try it with both guns 5" barrel, ie 1160fps for the 9mm ...
or both 4" barrel, ie 800fps for 45ACP.

 

[NikatKimber]

Now try it with both guns 5" barrel, ie 1160fps for the 9mm ...
or both 4" barrel, ie 800fps for 45ACP.

I used those numbers because the source had velocity data for muzzle, 25, 50, 75 and 100 yards.

If I used the 1220fps value listed earlier, then it returns 9mm with 5.4% higher KE @ muzzle, and .45acp with 22.6% higher inertia @ muzzle.