Gelatin test says 9mm = 45ACP for SD?

Here how I got there.

I think I am misleading all in my use of the term "energy dump". Perhaps there is a better way of putting it.

The energy I am referring to is the "unstoppable" momentum of a mass. An object in motion tends to stay in motion and all that.

Let's assume all the handgun bullets are hollowpoints. All are assumed to open upon impact. All are assumed to remain in the target and not exit.

1. Part of the energy stored in the moving bullet is expended by penetrating the highly elastic wall of the target.

2. Part of the energy is expended in order to continue the drive of the bullet forward, with sufficient force to cause the petals of the hollow point to bend back and open.

3. Part of the energy is expended to continue the opened hollowpoint on its path of destruction, further into the target, pushing the opened bullet through the mass of the target, be it bone or muscle tissue or both.

And part of the energy is is expended to push aside soft tissue in the form of temporary or permanent cavity deformation.

The likelyhood of a .45ACP making it through an arm and into the chest cavity with sufficient penetration to do the job is, with its larger store of energy, much more likely than with the lower energy .380ACP round.

The stored energy is what makes it happen, I would think.

The likelyhood of a .45ACP making it through an arm and into the chest cavity with sufficient penetration to do the job is, with its larger store of energy, much more likely than with the lower energy .380ACP round.

The stored energy is what makes it happen, I would think.

Click to expand...

Actually, momentum is more important than kinetic energy when you are calculating penetration. A round with higher momentum (weight times velocity) will have greater penetration (everything else being equal.)

A round with higher kinetic energy, that expends all it's kinetic energy (ie. no exit) obviously transfers more kinetic energy to the BG, but there is no evidence that the extra kinetic energy, at handgun levels, causes any increased efficacy with regard to stop times.

Efficacy is a function of two main things. Central nervous system damage and oxygen deprivation through pulmonary system damage.

The fastest most effective stoppage is through disconnection of the central nervous system. This is one of the primary reasons to have adequate penetration...ideally penetration on the chosen path vs. deflection.

Hole placement, size and quantity, are critical factors in oxygen deprivation. That is where expansion, tissue damage and wound channel become important.

Kinetic energy plays a role in tissue damage and wound channel, but it isn't as important as shot placement and bullet expansion when reviewing the differences in energies of typical pistol rounds.

The mechanics that you are talking about are several fold. One, a hollow point opens up through hydrolic force. Water, does not compress. So, as a bullet is penetrating tissue which is water laced, the water that is fed into the hollow point must escape to somewhere. Since more and more water is being forced into the hollow point from the front, the easiest escape round is through the side walls. This is how the mushroom occurs.

Also, penetration is most directly effected not by mass and velocity as it is effected by sectional density.

http://www.firearmstactical.com/tacticalbriefs/volume4/number1/toc.htm

In simple terms, it is the mass of the projectile relative to its diameter. For instance, a 135gr 9mm bullet has much better sectional density than a 135gr .40 bullet. Thus, more momentum is concentrated into a smaller focal point making penetration easier.

Energy plays a part in all this, but bullet design and construction have a much bigger role than energy.

Also, penetration is most directly effected not by mass and velocity as it is effected by sectional density.

http://www.firearmstactical.com/tact...umber1/toc.htm

In simple terms, it is the mass of the projectile relative to its diameter. For instance, a 135gr 9mm bullet has much better sectional density than a 135gr .40 bullet. Thus, more momentum is concentrated into a smaller focal point making penetration easier.

Click to expand...

True...which is why a lighter, smaller diameter bullet penetrates thin barriers better....however.....once you factor in expansion, the sectional density changes...and you always want expansion...the more the better (until it causes insufficient penetration.)

So while a 115 gr. 9mm might have better sectional density for the first inch of travel, it quickly can end up with less sectional density as it expands and loses energy. This is why a 1400 fps 115 gr. 9mm might penetrate a barrier better, but not penetrate as deeply through flesh and bone as a 230 gr. .45 at 950 fps. Likewise, this is why my 9mm's are loaded with 147 gr. loads which have considerably better sectional density than 115 gr. bullets, after expansion.

I'll remember this the next time I'm attacked by a block of gelatin.

Just because you found 'a' 9mm defensive load that 'matches' 'a' .45 defensive doesn't make it a blanket equivalency. All premium defensive ammo, 9mm or higher penetrates enough for PD use. Then it becomes a question of cavity trauma.

And I know it's all about shot placement. I'd rather have a well-placed .45 shot. (Or several.)