This is a broad overview of lethality and stopping power in ammunition, including information about stopping power and penetration


Why are bullets that penetrate less than 12 inches in Ballistic Gelatin considered ineffective? How does penetration factor into stopping power? Why are the benchmarks set so seemingly high?

The Physics of Ballistics is weird. Ballistics in general, is a science that contributes to projectile and ammunition design that  is evolving and getting better at delivering stopping power. This is true of hunting projectiles, defense and duty projectiles and other use cases. 


There is a lot of misinformation, and there is a lot of information that is publicly acknowledged and still not comprehensive because the education process is substantial, and because a majority of the understanding of why something is, in a ballistic performance perspective, is hard to explore deeply without understanding a lot of different things. 


There are a lot of reasons that penetration is a metric used to help identify stopping power; why ballistic gelatin is used as a benchmark testing media, and why the benchmarks are seemingly a bit off-base. 


Here are some background factors about the concepts we are exploring regarding lethality and stopping power in ammunition choices: 


AN IMPORTANT FACT: Stopping power is an equation that involves a lot of variables. And there is no reliable or repeatable formula or scientific baseline for determining it.  


Additional information:


  • Stopping power is about incapacitating a target – targets vary
  • A reliable metric which can help identify general stopping capabilities is blood loss – the problem is in all of the varied targets one might be attempting to stop, there are different volumes of blood; furthermore, certain targets can function with less blood than others, based on certain other related variables, too
  • Mass of a projectile can create a different wound channel, but velocity, distance from muzzle, projectile coatings, designs and other variables can still affect wound channel width and depth, bullet travel pathways, etc.
  • Minimum penetration depth can help improve chances of hitting vital organs, or creating multiple wound channels, but it is not a reliable indicator for guaranteed stopping power, even if generally, deeper penetration is correlated positively with stopping a threat more efficiently
  • Layers of skin, layers of clothing, layers of armor and other factors can negatively impact penetration, and stopping power
  • Certain skin types (when referring to animal targets, such as in hunting), or the elasticity of human skin can dramatically reduce penetration as the initial impact of a bullet may be negatively impacted by skin/elasticity. Bullet wound pathway may negatively impat stopping power as well
  • Deflections, bullet/jacket separation and bullet material composition can dramatically impact ballistic performance, especially with regards to penetration depth and energy transfer, as well as stopping power
  • Studies can never take all variables into effect, and are not indicative of guaranteed metrics for stopping power, rather, they provide information which trends towards defining best practices, innovation, and evolving understanding about producing projectiles and loads capable of improving stopping power
  • The influence of drugs, deflections, body mass, body composition, and other things can dramatically impact stopping power from an absolute perspective – that is, whether a projectile is effective at stopping a given target in a given scenario – but that is not a repeatable set of variables with which to engage in a study
  • Location of a wound channel or projectile hit on a target can dramatically impact positively, the ability to stop a target – a spine hit, or a brain hit or a facial hit, or even a hit to the heart or which severs an artery will almost immediately incapacitate a target, generally, whereas, a much larger, heavier projectile, or multiple hits to an extremity or outside of core organ areas may allow a target to survive completely, or for much longer before being effectively stopped
  • Energy delivery and velocity have outlier information that can show an overabundance of energy delivery on target or enough velocity can be immediately incapacitating for a certain size or mass of a given target, but again, not 100% of the time on all targets in all circumstances
  • Multiple wound channels in a core body area is generally considered a best practice for stopping a threat, but it too, is not a conclusive solution, as there are many anecdotal, and scientifically notated proof of cases where the target was not immediately neutralized


So, what’s the point here? Stopping power is not a definitive science backed by guaranteed variables that when employed will always stop a target. However there are best practices, trending pieces of data, and opportunities for optimizing a shot on a target if you want to improve stopping power from a percentage efficacy perspective. 


Here are some of those trends, pieces of data, and best practices regarding ballistic performance:


Concept: You can’t stop what you don’t hit. 


Background: So, most trainers and shooters train to shoot for the areas where they will impact the target they intend to stop, accurately and competently. This means that while you may almost guarantee stopping power by severing a spinal cord, you won’t ain for that 1.5” target in the heat of a gun battle, instead op[ting for multiple shots in the chest. 



Concept: You want more penetration, because it systematically lessens the chances of missing a vital organ, or hitting a crucial pot within a target’s body.


Background: If you have deeper penetration, you have better chances of hitting something else that can rupture, bleed out, or otherwise make survival impossible, so the best practice is to have penetration beyond the standard minimum. In this case, that standard for law enforcement is generally accepted as more than 12” in ballistic gelatin, which equates to about 9 inches or so of penetration into soft tissue in a human target. If you create a wound chanel more than 9 inches long, and in a core body area, you are likely to hit a spleen, liver, lung, etc. This additional damage may help to stop a heart (loss of blood), put the target into quicker incapacitation from energy delivery or total damage, etc. 


Concept: Ballistic Gelatin is a quasi-equivalent of the varied bone and muscle and soft tissue density that is comprised of all the different materials and organs, skin, and tissue in the body, and is much more consistent in predicting penetration, which helps to improve this chance of internal damage and total destruction in the wound channel.  


Background: Ballistic Gelatin is NOT a 1:1 replacement or testing medium for human tissue density – it is a constant variable that approximates the conglomeration of tissue densities and bullet behavior in the standard target, generally. 


Concept: More mass equals better penetration. 


Background: the physics of it, all things equal indicate that better penetration will be achieved at substantially similar velocities and environmental variables. And we know that this is not ALWAYS the case. However, generally, greater mass at same velocity offers better intrinsic delivery and penetration. This is a generally accepted physics concept. 


Concept: Some hypersonic velocity projectiles can have an immediate and devastating impact on total stopping power.


Background: It is more common than not, that an “overkill” effect is common, when the velocity of a projectile far outweighs the minimal velocity to penetrate a particular target. A cartridge offering 4500 fps velocity at the same grain weight may improve the total destructive capability of a projectile in soft tissue, than say, a projectile traveling at 1000 fps, for example. This is a documented and proven concept, but the science behind it is just now starting to be explored more fully. Soft tissue damage is irreparable in some instances when extreme velocity are used relative to similar projectiles, with lesser velocities. The wound channel profiles are significantly enhanced.


Some final notes about ballistics for self protection and terminal performance: 


Regarding stopping power and lethality generally: rapid blood loss is about the best benchmark for obtaining rapid stopping power. 


Sure, it’s possible to snap an animal’s spine, or burst its heart, or have a similar effect on a human defensive target, but it’s a much harder shot to make, generally. 

Wound channels, organ disruption and multiple shots are the quickest methods to achieve rapid blood loss.


The FBI is the organization that “sets trend analysis” for the broader law enforcement community – they have decided that the 12” penetration variable is the appropriate one based on data they have studied. 


If threat stoppage is the ONLY outcome desired, it is almost always preferable to have significant penetration as an ancillary or primary variable. This may not be the case if you have friendly fire concerns, live in a densely populated, closely built neighborhood, or have family in the background of where you shoot – so the decision to choose penetration over all else, or overpowered rounds over all else is not cut and dry.


Legalities are difficult to navigate. Make sure you are aware of the self defense guidelines and the law in your area. 


Physics has “absolute” laws. But it’s important to remember that absolute laws are general guidelines in behavior, not guarantees of the exact same outcome at all times. You need to determine which option you want, and identify that option from a field of competing offerings that offer the baseline performance and ballistics you think meet your minimum standard. 


You can, and should train to understand how to handle your firearm and the ammunition and projectiles you intend to use in that firearm. More training absolutely equals a better chance at stopping a threat. 


Evaluate the things you read and hear and see, with the gut test first; science second, and trending data third. Then do your own experimentation at the range and see what there is to see, or look into the empirical evidence that exists to support marketing claims, hearsay and legends about the product.