The great bullet debate*

Stopping power — in the movies and on TV you see humans being shot by handguns and blasted across rooms and through windows.   The bad guys almost always die immediately, and the good guys almost always live long enough to give some final words to a friend or loved one.  It doesn’t happen that way.  If the bullet has enough momentum to slam the person being shot up against the wall or flat on their back then the person shooting the gun would experience the same momentum in the reverse direction.  Handguns do recoil — but it’s manageable.   If the person shooting the gun doesn’t get slammed up against the wall the person getting shot won’t either.

“Stopping Power” is not easily measured and has been highly debated for many years. I have done a bunch of literature research and have answered the question sufficiently for myself.  This page is to help you decide for yourself.

Basically there are two sides to the debate (Greg Hamilton of Insights has a third, which I suspect has a lot of merit).  If you are interested in the great pistol bullet debate take a look at Dale Towert’s Stopping Power Page [the original link is dead but this can be substituted—Joe July 2, 2013] as a starting point. Then get a copy of Duncan MacPherson’s book Bullet Penetration for the other side of the debate.  See also: and [I have no substitute for this dead link—Joe].

If you are not interested in an overview of the debate, just skip to my conclusions.

Some people select their cartridge on the basis of momentum. In IPSC events momentum is rewarded via what is called Power Factor.   It’s not really power in the physics sense, but that is what they call it.   Power Factor is mass in grains times velocity in feet per second divided by 1000.   IPSC has three classifications for the guns used in matches, Minor is >= 125 PF, Major is >= 175 PF, and “get out of here” is < 125 PF.  Most .45 loads will make Major.  9 x 19,  .38 Special, and many .40 S&W loads only make minor.  This tends to reward heavy but slower moving bullets more than light weight, fast moving bullets.

Some people select their cartridge on the basis of energy.  I’ve seen some States tell hunters their cartridge selected must have a minimum amount of energy in order to take a particular type of game.   This tends to reward the light weight fast moving bullets.

One side says fast (light weight) bullets, if they penetrate “deep enough”, are best. This side thinks that if you get a bullet to hit at > ~1300 fps the temporary cavity causes it’s own damage in the form of blood pressure spikes, and temporary nervous system disruptions in various forms to cause things to happen which will be out of proportion to that which can be explained by blood loss and nerve damage.  The measure of this effect is closely approximated with bullet energy.

The other side says heavy bullets, if they don’t over penetrate, are best. It’s all blood loss and nerve damage (brain and spinal column being target rich environments for nerves). The ‘special’ effects of high speed bullets don’t show up until you get to rifle velocities (~2000 fps).  Hence the heavy bullet people want the largest volume of tissue traversed by the bullet. This is nearly always accomplished by the heaviest bullet your handgun can shoot with maximum weight retention after expanding to approximate double it’s original diameter.   This effect is closely related to bullet momentum (actually it’s roughly proportional to the bullet weight times the velocity to the 0.6 power).

Greg Hamilton’s hypothesis is that tissue is destroyed is the measure of stopping power.  But there is more to tissue being destroyed than just crushing (the “permanent cavity” in the vocabulary of the debaters) as the bullet travels through the tissue. He claims that when the tissue has to move out of the way at a speed faster than the speed of sound in that tissue the cellular membranes will be destroyed by the shock wave. If you remember the speed of sound in water is about 5000 fps and since it’s probably about the same in animal flesh you might wonder how any conventional bullets can manage this. The answer is the flesh must move at least partially perpendicular to the path of the bullet. This can greatly speed up the velocity. To illustrate: A water skier can easily average twice the speed of the boat by skiing from back and forth from side to side, covering twice the total distance the boat does in the same time. A FMJ bullet has a front end that basically doesn’t speed up the flesh as much as a flat nosed or an expanded HP bullet does. The FMJ pushes the flesh aside, the flesh stretches and finally ruptures enough to allow the passage of the bullet. Nearly all at a speed less than that of sound in the tissue.  The flesh then contracts back to nearly it’s original position. A jagged, flattened bullet causes lots of high speed movement of the flesh, destroying nearly everything in it’s path.  Hence Greg hypothesis is that neither energy or momentum is the critical item.  Almost any bullet that expands well and penetrates into the vital organs will work well.


I go with what everyone agrees on, if you are concerned about “stopping power” your efforts should be spent on the range practicing rather than looking for a “magic bullet”. I have heard this expressed many ways, in IPSC they say, “You can’t miss fast enough to win”. Others have said, “A hit from a .22 is more effective than a miss from a .44.” Greg Hamilton (somewhat tangential) says “Do you know how to double the effectiveness of any bullet? Put another round through your target.”  A more to the point quote from Hamilton is:

The entire discussion of “stopping power” is both stupid and irrelevant.   Statistics cannot be applied to individuals. People that need to be shot need to be shot soon and often. They need to be shot until they run out of fluid, brains, or balls.

If during the time you were reading the latest “stopping power” article you were instead practicing to save your life you would be far, far ahead.

Greg Hamilton
May 08, 1998

For self-defense your first criteria in a handgun cartridge should be reliability in your firearm. Next, it should be the largest caliber you can shoot quickly and comfortably.  Next it should be accurate enough to get the job done (two inch groups versus four or six inches groups at 25 yards probably doesn’t matter). Next it should be of expanding technology, rather than FMJ — reliability may be an issue in this trade off. If you really feel the need you can test the expanding characteristics of your bullet very easily. A couple of milk jugs filled with water will closely duplicate the ability of a bullet to expand in flesh — BUT NOT IT’S ABILITY TO PENETRATE. Put a layer or two of clothing (or other material you think you might be shooting through) in front of the first jug. Some HP’s will plug up and act as a FMJ after acting as a cookie cutter going through some materials.  Some types of obstructions will damage and slow bullet down enough to cause it to fail to expand. Car doors and window glass are good examples of this.

*This originally appear on a web page of mine. I am moving it here for better visibility and archival.—Joe July 2, 2013