The shotgun is an extremely versatile tool and with the correct ammunition the shotgun is far more effective than handguns for home defense but there is a wide variety of ammunition available for it. In this article I discuss how to choose between bird shot, buck shot and slugs for self and home defense.

Terminal Ballistics

To get the most out of this article you should have some basic knowledge about terminal ballistics (the effect of the bullet on the target). In a previous post titled “A primer on handgun terminal ballistics” I presented an overview of terminal ballistics.

The key thing to take away is that firearms stop threats including humans by penetrating them and destroying tissue and organs. If a bullet doesn’t have enough momentum to penetrate the bad guy it wont be effective in stopping him.

The FBI has determined that to effectively stop a human a projectile must penetrate a minimum of 12 inches with up to 18 inches preferred.

12 gauge or 20 gauge?

A common question is whether a person should purchase a 12 or 20 gauge shotgun for home defense. I recommend that for home defense a 12 gauge be used because it delivers more projectiles to the target, there is a wider selection of ammunition, and the fact that there are reduced recoil or tactical 12 gauge loads that greatly reduce the recoil of the 12 gauge.

2 3/4 inch or 3 inch shotgun ammunition?

For the 12 gauge both 2 3/4 inch and 3 inch ammunition is readily available, the 3 inch ammunition is sometimes referred to as “Magnum.” For home defense 2 3/4 inch ammunition is better. The 3 inch ammunition has greatly increased recoil which makes follow up shots harder, decreases the capacity of the shotgun, and may prevent women or children from using it due to the recoil.

Available Ammunition Types

Birdshot

Birdshot consists of many small projectiles ranging in size from .080″ to .23″ in diamater. Birdshot is the most common ammunition because it can be used for hunting birds, target practice and skeet shooting. Birdshot is numbered and the smaller the number the larger the projectiles.

(table from Wikipedia)

Buckshot

Buckshot is essentially a scaled up version of bird shot and also contains multiple projectiles but they are both larger and heavier, making it suitable for use on Deer. Buck shot is numbered similarly to Birdshot, with shot size increasing as the number decreases. The most common sizes of buckshot are #00 (double ought) and #000 (triple ought).

Buckshot tends to have considerable recoil, recently several companies including Remington and Federal have introduced reduced recoil or tactical buckshot.

(table from Wikipedia)

Slugs

Unlike Birdshot and Buckshot which have multiple projectiles, the slug is a single projectile. Slugs have a higher effective range and can be used where a spreading pattern is not desired. Because of their massive momentum and energy they are also effective against bears. There are several different types of slugs, expanding, non expanding, rifled, and non rifled.

Ammunition Performance

For reference a 9mm handgun with 115 grain bullet produces:

Energy: 367 ft/lb
Momentum: 19.71
Velocity: 1200 FPS

12 Gauge Birdshot Ballistics

Birdshot is often recommended as a limited penetration ammunition for nervous home owners or apartment dwellers that want to avoid over penetration. In this section I evaluate the potential of birdshot for home defense.

Birdshot Terminal Ballistics Calculations

Let’s do some terminal ballistics calculations on the potential birdshot, I’ll use #4 shot as it is the heaviest commonly available birdshot load. In this case I’m using numbers from Federal’s Game-Shok Heavy Field Load.

Federal indicates the load fires 1 1/4 OZ (546 grains) of #4 shot at 1220 FPS

Overall Energy: 1804 ft/lb
Overall Momentum: 95

These numbers appear very impressive and far eclipse the 9mm handgun but there is a problem, bird shot does not behave as a single projectile even at point blank range, in fact there are 167 individual projectiles with a 1 1/4 oz #4 shot load. As a whole birdshot has massive momentum, but each individual pellet weighs only 3.2 grains, meaning they have VERY little momentum and don’t penetrate very well as they give up their energy very quickly.

Let us now calculate the momentum and energy of a single birdshot pellet:

Pellet Energy: 23.12
Pellet Momentum: 0.82

This paints a drastically different picture, having minimal energy, and very little penetration which is what we would expect of ammunition designed for birds. That said these numbers also don’t paint an entirely realistic picture because there are 167 pellets striking a fairly small area the performance will be better than a single pellet.

So to get a look at how birdshot performs as a ballistic gelatin test is necessary. Ballistic gelatin is used to approximate tissue and bones of animals to test ammunition. Tacticalworks (a respected information site on ballistic tests) did a test with #4 birdshot (full results here). Here are the results:

Range: 3 yards
Shotgun: 18 inch barreled Remington 870 Marine Magnumn
Round: 12 gauge Remington Heavy Dove 1-1/8 oz #4 Birdshot
Gelatin: 9′x9′x19′ 10% ordinance gelatin block
Measured Average Permenant Cavity: 6.5 inches (16.5 cm)
Temporary Stretch Cavity: 0.0 to 6.0 inches (0.0 to 15.2 cm)

Conclusion:

Bird shot is for birds, not people people!

Even the #4 heavy bird shot load at 3 yards did not penetrate sufficiently to reliably stop an attacker, remember the FBI defines minimum acceptable penetration as 12 inches with 18 inches preferred.

Bird shot should never be used for a home defense load, all bird shot loads lack both the momentum and penetration required to reliably stop a human attacker. This really shouldn’t be a surprise to anyone because bird shot is designed for lightweight game, if the pellets were capable of stopping a human it would devastate the small animal and not leave much to eat.

While the intentions of people who recommend bird shot are usually good they usually lack a fundamental understanding of terminal ballistics and unintentionally give horrible advice. They often site examples of bad guys being shot with bird shot breaking off an attack, the important thing to realize is that in almost all cases the attacker chose to stop the attack, he was not forced to stop.

At the end of the day you must realize that anything that will penetrate a human enough to force them to stop an attack is going to also penetrate walls. The best way to avoid this is to prevent the situation where you must shoot, and practice enough to reliably hit the bad guy in a defensive situation.

Fortunately there is a version of bird shot scaled up to a size that is effective on people, it is called buckshot!

12 Gauge Buckshot Ballistics

Many deer are the same size or slightly larger than human sized so it makes sense that ammunition developed for them would be effective on humans. Buckshot is often use very effectively in home defense, the two most common sizes are #00 and #000.

#00 buckshot terminal ballistic information

#00 buckshot has a pellet diameter of .33 and a weight of 54 grains (16.8 times more mass than a #4 birdshot projectile) and each cartridge typically contains 9 to 12 projectiles. For these calculations I’ll use Federal Power-Shok Low Recoil Ammunition 12 Gauge 2-3/4″ Buffered 00 Buckshot 9 Pellets at a velocity of 1140 FPS

Overall Energy: 1402 ft/lb
Overall Momentum: 79.14

If you considered only the overall energy and momentum it would appear bird shot would perform better, but remember, neither bird shot or buck shot is a single projectile so lets now look at an individual projectile:

# Projectiles: 9
Projectile Weight: 54 grains (16.8 times more than #4 birdshot)
Projectile Energy: 155 ft/lb (6.7 times more than #4 birdshot)
Projectile Momentum: 8.79 (10.71 times more than #4 birdshot)

As you can the individual projectile performance of buckshot is much greater than birdshot, but like birdshot because there are multiple projectiles we need to look at an overall picture, luckily tacticalworks also did ballistic performance testing of #00 buckshot (full results here).

Range: 3 yards
Shotgun: 18 inch barreled Remington 870 Marine Magnumn
Round: 12 gauge 2? Federal Classic 00 Buckshot (9 pellets)
Gelatin: 9′x9′x19′ 10% ordinance gelatin block
Measured Average Permanent Cavity Penetration: 22.3 inches (56.6cm) (3.4X further than #4 birdshot)

Conclusion:#00 buckshot penetrated to 22.3 inches (3.4X further than #4 birdshot) making it an excellent choice for home defense.

12 Gauge Slug Ballistics

Unlike birdshot and buckshot a slug is a single massive projectile, it can be used for deer hunting and has been used very successfully against black and even bigger bears.

12 Gauge Slug Terminal Ballistics Information

I’ll be using the Brenneke USA K.O. Ammunition 12 Gauge 2-3/4″ 1 oz Foster-type for these calculations

Projectile Weight: 437.7 grains
Velocity: 1600 FPS
Energy: 2184 ft/lb
Momentum: 100

tacticalworks also did a ballistic gelatin test with a 1 OZ foster slug here are the results (full results here).

Range: 3 yards
Shotgun: 18 inch barreled Remington 870 Marine Magnumn
Round: 12 gauge 2 Winchester Foster Style Slug
Measured Average Permenant Cavity Penetration: 17.0 inches (43.2cm)
Measured Temporary Stretch Cavity: 0.5 to 15.5 inches (1.3 to 39.4 cm)

Conclusion

The slug has massive momentum and energy, because this is an expanding slug the penetration was somewhat restricted to 17.0 inches making it an excellent option for home defense.

Overall Conclusion

Birdshot is woefully inadequate for home defense and should not be used except for target practice and bird hunting.

Buckshot is an excellent performer and has a proven track record. Buckshot is a better choice than a slug for general self defense because it does not depend on expansion to limit its penetration.

Expanding foster type slugs are also an excellent performer with massive momentum but non expanding or slugs that fail to expand have the capability to over penetrate due to their mass and momentum. Slugs are best used when a single projectile is required because multiple projectiles spreading would not be appropriate and for longer range shots.

I believe it is responsible to have both buckshot and slugs available with a defensive shotgun, the TacStar SideSaddle mounts to the side of the receiver and allows you to carry extra ammunition, in my case I load buckshot in the shotgun and carry slugs on the side saddle so that I can selectively use them.

With the exception of religion there is perhaps no greater debate than that of the defensive handgun caliber. In this article I compare the ballistic information of 9mm Luger, 40 S&W and 45 ACP.

With the amount of opinions on handgun calibers it can be difficult to obtain solid information. After reading this article you will have valuable information about how the three common self defense calibers compare to each other.

To get the most out of the information below you should have a basic understanding of some terms, specifically energy, momentum and sectional density and velocity.

This subject is highly complicated and large amounts of information have been created on it.  It is my goal to give you information on theoretical performance of the various calibers with bullets of similar construction and other factors the same, this is highly valuable for comparing calibers and loads to each other but may not translate into real world performance.

Bullet construction, weight, shot placement, physical construction and the mental makeup of the bad guy all play huge parts in how many shots and how long it will take to stop him or her (some people pass out when shot, others can stay in control for long periods of time).

Terms

Grains: A measurement of weight, there are 7,000 grains in one pound. The weight of the bullet measured in grains and is printed on boxes of factory ammunition.Energy: Measured in ft/lbs this is the kinetic energy of a bullet or how hard it hits, this number is often promoted heavily on ammunition boxes. You can calculate energy by: Energy = ((Bullet Weight * Bullet Weight) * Velocity) / 450400.

Momentum: Momentum is a product of velocity and the mass of an object, the more momentum something has the harder it is to stop it, this is why it is harder to stop a semi truck than a passenger car. You can calculate momentum by doing: (Bullet Weight / 7000) * velocity

Because momentum is a factor of both velocity AND mass this means that a heavier bullet, though traveling slower may have higher momentum and thus perform better.

Sectional Density (SD): Sectional density is essentially the bullet size to weight ratio. Bullet weight alone is not enough to calculate performance, you must also take into consideration the width of the bullet. A 180 grain bullet with a width of .401 has a higher width / weight ratio than a 180 grain bullet of .451. You can calculate sectional density by: ((Weight / 7000) / (Diameter * Diameter)

Velocity: Measured in feet-per-second (fps) this is how fast the bullet is traveling. The same ammunition will develop different velocities in different guns so the velocity printed on the box is only an estimate, in reality it is often less. You can measure the velocity of a bullet by shooting it over a Chronograph

Terminal Ballistics

Terminal ballistics is the study of the effect of a bullet on the target, in the case of self defense this is often another human or small animal such as a dog.

In a previous post titled “A primer on handgun terminal ballistics” I presented an overview of terminal ballistics; having a grasp of the information presented in that post would be helpful but is not required to benefit from this article.

Meeting the 9mm, 40 S&W and 45 ACP

The three commonly available self defense calibers are the 9mm Luger, 40 S&W, and 45 ACP. All three calibers have strengths and weaknesses and each higher passionate supporters.

9mm Luger

Often referred to as just “9mm”, the 9mm Luger was adopted by the German military in 1908 and today it is in use by police departments and militaries (including the U.S) all over the world. In the U.S. the 9mm is popular for self defense because of tame recoil, high capacity and affordable ammunition. Find out more about the 9mm Luger.

The 9mm fires bullets .355 inches in diameter, common bullet weights are: 115, 124 and 147 grains.

40 S&W

The 40 S&W was introduced in 1990 in response to a call by the F.B.I for a caliber more powerful than the 9mm Luger yet still able to fit in smaller handguns with mangeable recoil. The 40 S&W’s goal is to deliver my power than the 9mm Luger with less recoil and higher capacity than the 45 ACP. The 40 S&W has been widely adopted by police departments and federal agencies throughout the U.S. Find out more about the 40 S&W.

The 40 S&W fires bullets .401 inches in diameter, common bullet weights are: 155, 165 and 180 grains.

45 ACP

Designed by John Browning in 1905 and adopted by the military in 1911, the 45 ACP is the oldest of the common self defense calibers and fires the heaviest bullets of the three. The 45 ACP is popular among those who prefer larger, and heavier bullets. Find out more about the 45 ACP.

The 45 ACP fires bullets .451 inches in diameter, common bullet weights are: 185, 200 and 230 grains.

Down to business (ballistic comparison)

Now that you have a understanding of some terms and have met the calibers lets get to comparing the calibers. I will present energy, momentum, sectional density and velocity information for each common bullet weight in each caliber.

I will use published velocities from Speer’s Gold Dot line of ammuntion, Gold Dot ammunition is extremely popular with both law enforcement agencies and civilians. In 9mm Luger and 45 ACP I will use +p ammunition for bullet where it is available.

+p ammunition is ammunition loaded to higher pressures than the caliber originally supported, modern firearms are capable of higher pressures so +p ammunition standards have been created for the 9mm and 45 ACP. I will not use or condone using +p+ ammunition because it is not officially recognized and there is no standard (each manufacturer can define it differently).

9mm Luger

115 grain JHP

Energy: 367 ft/lb
Momentum: 19.71
Sectional Density: .130
Velocity: 1200 FPS

124 grain +P JHPEnergy: 409 ft/lb
Momentum: 21.61
Sectional Density: .141
Velocity: 1220 FPS

147 grain JHP

Energy: 316.65 ft/lb
Momentum: 20.685
Sectional Density: .167
Velocity: 985 FPS

Conclusion:

The 124 grain +p 9mm Luger load has the most momentum and the most energy, making it the most capable of the 9mm loads.

40 S&W

155 grain JHP

Energy: 475 ft/lb
Momentum: 26.01
Sectional Density: .138
Velocity: 1175 FPS

165 grain JHP

Energy: 485 ft/lb
Momentum: 27.10
Sectional Density: .147
Velocity: 1150 FPS

180 grain JHP

Energy: 387 ft/lb
Momentum: 25.32
Sectional Density: .161
Velocity: 985 FPS

Conclusion:

The 165 and 155 bullet weights should perform best in 40 S&W, the 165 grain bullet is the leader with slightly more momentum and energy. Despite being heavier the 180 grain bullet boasts both less momentum and less energy because velocity dropped faster than the heavier bullet could make up for.

45 ACP

185 grain JHP

Energy: 452 ft/lb
Momentum: 27.75
Sectional Density: .130
Velocity: 1050 FPS

200 grain +P JHP

Energy: 517.93 ft/lb
Momentum: 30.85
Sectional Density: .140
Velocity: 1080 FPS

230 grain JHP

Energy: 404 ft/lb
Momentum: 29.24
Sectional Density: .162
Velocity: 890 FPS

Conclusion:

In 45 ACP the 200 grain +p load offers the most momentum and energy, making it an excellent choice, the 230 grain JHP is the second pick because it has more momentum and higher sectional density than the 185 grain bullet.

Overall Conclusions

The heaviest bullet is not the winner for any of the three calibers (9mm, 40 S&W or 45 ACP) this is because there is a point of diminishing returns where added bullet mass decreases velocity faster than the extra weight can increase momentum.

All 40 S&W and 45 ACP loads offer significantly higher momentum than the 9mm, this is expected because they have heavier bullets.

Final Thoughts

Choosing a defensive caliber is similar to selecting a spouse. Picking the first one you come across is seldom a good idea, you should shoot each of the calibers and pick the one you like the most. Ballistic information such as I presented above is important but more so is your ability to be accurate with the caliber and to be comfortable shooting it.

Any of the above calibers are very capable of stopping an aggressor but the shooter must do his part. Each have benefits, the 9mm is cheap to shoot with low recoil and high capacity, the 40 S&W delivers more punch then the 9mm in a package that is typically smaller than the 45. The 45 delivers the most energy and momentum to the target but typically trades capacity and has higher recoil.

The 45 ACP has another benefit over the 9mm, the unexpanded 45 ACP bullet is nearly as big as a fully expanded 9mm, this means even if your bullet fails to expand it contact nearly as much tissue as a fully expanded 9mm. This is an important consideration because even with modern bullets failure to expand is still fairly common.

I carry either the 40 S&W (75%) or the 45 ACP (25%) depending on the task at hand. While the 9mm is less powerful it is still capable and I don’t exclude it from carrying, in fact my wife’s CCW is a 9mm Springfield XD.

The 9mm is the minimum caliber I recommend for use as a primary defensive handgun, the .380 ACP is extremely popular as a backup gun but it uses lighter and slower bullets than the 9mm and in my opinion sacrifices too much momentum to be considered as a primary caliber. Additionally .380 ACP pistols tend to be very small which increases felt recoil, often beyond that of the standard 9mm.

It is my hope this article has answered some of your questions and may help you refute some of the claims made by passionate but uninformed gun owners.

The 40 S&W is a descendant of the 10mm cartridge which was developed in response to a call from the FBI for a cartridge with more power than the 9mm with higher capacity than the 45. The 10mm delivered very well, unfortunately it met resistence in the FBI due to stiff recoil and large sized handguns.Smith and Wesson shortened the 10mm cartridge case, reduced velocity and the 40 S&W was born. Because the 40 S&W case is shorter than the 10mm it can be chambered in 9mm size handguns, a benefit for agencies that were using 9mms.

The 40 S&W was introduced in January, 1990 and today is the most common law enforcement caliber. Some of the reasons the 40 S&W are so popular are:

#1 Delivers significantly better terminal ballistics than the 9mm

#2 Higher capacity than the 45 ACP

#3 Is chambered in 9mm sized handguns.

Find out more about 40 S&W

There is a lot of misinformation surrounding firearms industry, usually coming from a gun dealer or a helpful but misinformed friend or family member. This article explains some of the concepts of terminal ballistics and how they apply to handgun self defense.

Terminal ballistics is the study of the effect of a bullet on the target, in the case of self defense this is often another human or small animal such as a dog.

A knowledge of terminal ballistics will help you identify what information is correct, and what is biased or wrong.

There is a great deal of information available on the Internet about terminal ballistics on humans and some of the best can be found in a report the FBI released called “Handgun Wounding Factors and Effectiveness” which is an in depth discussion of terminal ballistics on humans.

This subject is highly complicated and large amounts of information have been created on it. It is my goal to give you a primer without overwhelming you.

Bullet construction, weight, shot placement, physical construction and the mental makeup of the bad guy all play huge parts in how many shots and how long it will take to stop him or her (some people pass out when shot, others can stay in control for long periods of time).

#1 Penetration and shot placement are king

Handguns stop a bad guy by penetrating his vital organs, if your bullet is incapable of reaching those organs no matter how well placed the shot it may not be effective. Shot placement is important because a bullet that is able to penetrate is not effective if not placed in vital organs.

Penetration

The FBI determined the ideal penetration range 18 inches with a minimum of 12 inches of penetration. People often worry about over penetration and make the statement that 18 inches is excessive, this is incorrect for several reasons:

#1 A handgun stops a threat by penetration, the temporary wound channel is not effective for handguns because the bullet is moving too slowly, without penetration a gun is ineffective.

#2 You may not have a perfect shot, while few humans are thicker than 12 inches from the chest to the back, a shot from the right side through requires more penetration, shooting through barriers such as a coat, or arm also increases the required penetration

#3 You don’t want the bullet to reach the vitals, you want it to destroy them, as a bullet slows it begins pushing tissue aside rather than causing damage, you want enough energy left to cause damage once the vitals are reached.

#4 America is getting bigger, recently the medical field increased the length of needles, the coast guard has had to recalculate capacity ratings of boats, all because Americans are getting bigger. The larger a person is there more fat and muscle the bullet must penetrate before reaching vitals.

Shot Placement

Shot placement means putting the bullet in an effective area, while many people advocate shot placement as the single most important factor I disagree and view penetration as slightly more important. Proper shot placement is insignficant if the bullet is unable to penetrate to vitals, likewise a bullet is not effective if it doesn’t pass through vital organs.

There are three shot placement areas:

Electrical: This is shooting the head, this is highly effective because it instantly disrupts the electrical system of the body, unfortunately head shots are extremely hard to deliver because the head moves from side to side and is a fairly small target. For self defense the head shot should rarely be the initial target.

Center of Mass (COM): This is the heart and lung area of the chest and is the primary shot placement area, it is a large area and doesn’t move much. COM should be the standard default target, COM hits work by causing the lungs and heart to stop working, this means the bad guy can have up to 15-30 seconds of willful control to do you harm. If COM hits are ineffective they can be followed with an electrical shot (see above).

Structural: These are hits to the frame of the body, for example to the arms or legs and are very ineffective at stopping a bad guy. A bad guy hit in a structural area may stop the attack, but if he does it is leisure. The goal of self defense should be to force the bad guy to stop his attack, not ask him to.

#2 Expansion can be a valuable aid

There are two primary types of bullets for handguns, Jacketed Hollow Point (JHP) and Full Metal Jacket (FMJ).

Jacketed Hollow Point bullets can dramatically increase the effectiveness of handgun bullets on humans, these bullets begin expanding once they hit the target, increasing the odds of doing damage to a vital organ, and also reducing the chances of the bullet passing through the target and injuring others. JHP bullets are extensively used by police departments both because of the increased effectiveness and to reduce shooting through the bad guy.

JHP bullets are particularly good for smaller calibers such a 9mm bullet is .355 inches in diameter, with 50% expansion the bullet is now .532 inches or slightly larger than a non expanded 45 ACP bullet (.451 inches).

The trade off for expansion is the larger bullet looses momentum more quickly and doesn’t penetrate as much, thus in very small calibers such as the .380 ACP FMJ may be a better choice.

Full Metal Jacket bullets do not expand when they hit the target and are used by the military (which are prohibited from using expanding bullets) and for target practice. Because FMJ do not expand they penetrate excessively and are not suitable for most self defense scenarios where the target is likely to be a human.

FMJ is a good choice for woods carry because the muscle of cats, wolves and bears can cause JHP to expand and not penetrate enough to stop the animal.

Energy, Velocity , Momentum and Sectional Density

There are several factors to consider when estimating ammunition performance, they are energy, velocity and momentum, energy and velocity are often printed on the box, unfortunately a more significant value momentum is not, luckily both energy and momentum are easy to calculate.

Energy: Measured in ft/lbs this is the kinetic energy of a bullet or how hard it hits, this number is often promoted heavily on ammunition boxes. You can calculate energy by: Energy = ((Bullet Weight * Bullet Weight) * Velocity) / 450400.

Momentum: Momentum is a product of velocity and the mass of an object, the more momentum something has the harder it is to stop it, this is why it is harder to stop a semi truck than a passenger car. You can calculate momentum by doing: (Bullet Weight / 7000) * velocity

Because momentum is a factor of both velocity AND mass this means that a heavier bullet, though traveling slower may have higher momentum and thus perform better.

Sectional Density (SD): Sectional density is essentially the bullet size to weight ratio. Bullet weight alone is not enough to calculate performance, you must also take into consideration the width of the bullet. A 180 grain bullet with a width of .401 has a higher width / weight ratio than a 180 grain bullet of .451. You can calculate sectional density by: ((Weight / 7000) / (Diameter * Diameter)

Velocity: Measured in feet-per-second (fps) this is how fast the bullet is traveling. The same ammunition will develop different velocities in different guns so the velocity printed on the box is only an estimate, in reality it is often less. You can measure the velocity of a bullet by shooting it over a Chronograph.

Estimating Ammunition Performance

There are several things that affect ammunition performance, velocity, momentum, and bullet construction are a few of the big ones. All bullets are not constructed equal, some brands of bullets with the same velocity and weight will perform different, expanding more or less, with more or less penetration. This section details how to compare the theoretical performance of bullets of similar velocity and construction on paper.

The Fallacy of relying on Velocity and Energy

When comparing ammunition in the store often only velocity and energy are available with numbers such as 1195 fps and 491 ft/lb of energy. The problem with these numbers is that by themselves they are not reliable indicators of performance.

One would think 491 ft/lb of energy would be enough to throw a person to the ground when shot, unfortunately this isn’t true and that is because for every action there is an equal and opposite reaction. Were the bullet able to throw the target to the ground the recoil would also throw you to the ground, and clearly most handguns are far from capable of that.

Velocity is also a poor thing to consider by itself, the 40 S&W is capable of pushing a 130 grain bullet to 1300 fps, unfortunately such a light bullet is unlikely to perform well.

What is the answer then? Two things, momentum and sectional density.

Consider the following 40 S&W loads (40 S&W bullet diameter is .401)

40 S&W 135 grain bullet at 1300 FPS

Energy: 506 ft/lbs
Momentum: 25.07
SD: .119

40 S&W 155 grain bullet at 1175 FPS

Energy: 475 ft/lbs
Momentum: 26.01
SD: .137

40 S&W 180 grain bullet at 1000 FPS

Energy: 399 ft/lbs
Momentum: 25.71
SD: .159

If you considered just the information printed on the box (the velocity and the energy) the 135 grain seems to be the clear winner, it is traveling faster with more energy than the other two loads, but once you calculate momentum and sectional density a different picture is painted.

Both the 155 and 180 grain loads have more momentum than the 135 grain load, and both have a higher sectional density meaning they should penetrate deeper and yield a better result.

Because sectional density is constant whereas momentum factors both mass and velocity I give it a higher weight than sectional density when evaluating loads.

Conclusion:

Every caliber has a sweet spot bullet weight with maximum momentum and energy, by using the principles in this article you can find that sweet spot In the case of 40 S&W it is usually 155 to 165 grains, after which momentum drops because velocity drops faster than the increased mass can make up for.