The versatility of the shotgun as a tactical tool owes largely to the stunning array of different ammunition choices available for feeding through the weapon. Many different sizes and configurations of projectiles are available; birdshot, buckshot, slugs, diversion devices, chemical payloads, beanbags, rubber projectiles�this list is not inclusive and it gets longer and longer almost every day. In this chapter we're going to explore in some detail the more common choices as they apply to a tactical application and negate much of the exotic stuff.
While the exotic shotshells such as diversionary devices, and breaching rounds are certainly interesting, instead we'll focus most of our discussion on conventional ammunition and how your choices can greatly impact the performance of a given load on the way towards and in target media. The reason for this focus is that we feel that not only is there a general lack of knowledge in this department, there are also dangerous ideas and misconceptions abound. Our objective is to introduce you to some of the fundamentals associated with selecting ammunition appropriate across a range of tactical applications.
This all being said, one form of "exotic" ammunition we will consider briefly is frangible. Constructed from material designed to disintegrate into dust upon contact with a hard surface, frangible ammunition is rapidly gaining popularity in training environments and merits consideration in the selection of ammunition deployed in a tactical role.
The variety and selection of conventional ammunition available for your shotgun is likely somewhat overwhelming, but there are some common starting points that are useful in navigating this veritable jungle. They all start with consideration of shot size.
Shot size likely the most important consideration in evaluating the wound generating capacity of a particular shotgun load. It is not an easy consideration either, as a dizzying array of different shot sizes are available. There are generally three different types of shot: birdshot, buckshot, and slugs. Birdshot is characterized by a large number of extremely small pellets. These loads are most useful in the hunting of small, fast moving game (such as flying birds). Buckshot is characterized as a smaller number of larger sized pellets and is typically used in applications where the target is larger animals. Slugs are considered as a single projectile, the same diameter as the inside of the bore. Table 5.1 illustrates the large variety of different shot sizes available.
There are two types of mass that are useful when considering ammunition selection for a tactical shotgun. Knowing both the total projectile mass and the mass of any one projectile is constructive in several different departments of your ammunition evaluation, the combined consideration of which ultimately allows meaningful insight as to the potential in-flight/ terminal ballistics of each projectile. The total shot payload mass can be useful in calculating the individual pellet mass (if you have counted the number of pellets represented by the total mass), and individual projectile mass is the important first half in being able to calculate kinetic energy and more importantly sectional density (both useful in evaluating wounding potential).
Total payload mass in a typical 12 gauge load is typically around 1oz (437.5 grains) with lighter loads weighing in at approximately 7/8 oz and heavier ones up in the 1-1/8 to 1-1/4oz range. Referring back to table 5.1 you'll notice the approximate individual pellet mass and number of pellets in a 1 oz load.
The type of material used to make a projectile is also important as different materials used in shot construction can have widely varying physical properties. These different can greatly influence the performance characteristics of the projectiles. Of significance are the physical characteristics of hardness and density. Density is important because it determines the mass of a pellet of a given caliber, and hardness is important because it governs how much the shot is deformed upon firing and when traveling through the target medium.
While there are many exotic materials used in shot construction such as bisthmus and tungsten, by far the most likely ones you would encounter are steel and lead. Lead is the most common material used for shot due to its high density and low cost. Steel is the second most popular material used in shot construction; however it lacks the density of lead and as such is ballistically inferior.
There is a significant difference in hardness between steel and lead shot. Lead is a relatively soft material and as such can deform significantly both when firing and when encountering the resistance of the target media. Lead ammunition can be run through virtually any gun and choke combination without risk. Steel on the other hand is an extremely hard material and has significant elastic memory. It is not safe for use in all shotguns, particularly older ones or those equipped with extra tight chokes.
Lead is significantly more dense (11.34 grams/cubic centimeter) as compared to steel (7.86 grams/cubic centimeter). Due to this higher density, lead is a vastly superior choice in material and should be chosen over steel for virtually all tactical applications. The reasons why will becomre evident a little later on when we talk about sectional density and kinetic energy.
Introduction of frangible ammunition to our discussion is appropriate when talking about shot material. Typically a matrix of finely ground copper particles fused together with a binding agent, frangible projectiles are gaining more and more popularity as both training ammunition and have many environmental and health advantages over conventional lead ammunition. There are also some benefits associated with reduced over-penetration in both target media and, in the event of a miss, modern building materials. As it grows in popularity and availability, frangible ammunition is something you likely to have on hand. As such it is worth understanding some of the performance characteristics of this ammunition and how they impact the ultimate tactical effectiveness of these rounds.
Velocity is a relatively important characteristic to consider when evaluating a particular load for a tactical application. Propellant gasses in the shot shell accelerate the shot/wad combination down the barrel, and these all leave the barrel at a speed coined "muzzle velocity". Velocity of the projectiles is highest at the muzzle of the gun, and as they travel downrange they encounter air resistance and will immediately and continually bleed speed. How much speed they lose is a function of their mass and their cross sectional area (sectional density).
The final velocity a given shot/wad combination is accelerated to also has a significant impact on the recoil generated upon firing. The higher the mass and the higher the velocity, the higher the recoil will be. This is an important consideration, as some 12 gauge loads are capable of generating recoil greatly in excess of what many shooters can effectively handle (3.5 inch magnum slugs come to mind). Many people get far too caught up on trying to maximize the mass and velocity variables and negate the effects of the consequential recoil on their ability to shoot accurately and quickly follow up if required. We'll talk more about this shortly.
Energy is a dangerous and controversial topic in when evaluating the potential effectiveness of a given projectile. Much has been written about the role of energy in wound ballistics, and unfortunately much of it is myth. The myths tend to center around the notion that the amount of kinetic energy "deposited" by a projectile is a measure of the damage it produces. This is misleading because many people lack sufficient technical education to differentiate between energy and force, and there is a large difference.
Duncan MacLean writes in his expertly recognized (yet unfortunately out-of-print) book Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma
"The reason that kinetic energy and damage are not always correlated is that dynamic damage is not due to energy absorption, but to stress (force per area). In many cases, absorption of larger kinetic energy causes larger forces and more damage, but this connection is by no means assured because many other factors come into play...
...Attempts to determine bullet effectiveness or assign wound trauma incapacitation assessing bullet kinetic energy are doomed to failure for two interconnected reasons:
- damage is done by stress (force), not energy
- an indeterminate, but usually large, amount of the bullet kinetic energy leads to tissue stresses that are not large enough to cause trauma
Dr. Martin Falker (another leading authority on terminal ballistics) also writes:
"A large slow projectile will crush a large amount of tissue, whereas a small fast missile with the same kinetic energy will stretch more tissue but crush less. If the tissue crushed includes the wall of a large blood vessel, far more damaging consequences are likely to result than if this vessel absorbs the same amount of energy in being stretched or temporarily displaced by cavitation."
Keeping in mind the cautions of both Fackler and MacPherson, in our opinion kinetic energy can in a very limited way be a useful indicator in that it allows an evaluation of the energy available for crushing tissue.
Kinetic energy is described by physicists in the following equation:
Ek = � mv2
Ek = kinetic energy (ft*lbs)
m = mass (mass = weight (gr) / 7000 (gr/lb) / 32 (ft/s2))
v = velocity (ft/sec)
You'll notice that there are but two variables: mass and velocity. In any given shotgun load, the energy imparted to the entire shot column is relatively the same. What varies in a big way is the energy imparted to an individual pellet. For example: when a 1 ounce slug is fired, most of the energy of the load is contained in one 437.5 grain projectile. In comparison, the average round of Tactical 00 Buck contains 8 - .33 caliber pellets. The total energy of the shotgun round is divided equally between these 8 pellets such that each pellet only has 1/8 of the total system. As a second comparison consider a load of #8 shot. While the total mass of the payload weighs in as the same 1 oz of lead, the energy now has to be shared between approximately 460 - .090 caliber pellets.
Applying our kinetic energy formula for each of these three examples, you can immediately see the enormous variation in muzzle energy of each individual pellet across some varying shot sizes:
|# Pellets||Projectile Mass
|.74 cal rifled slug||437.5||1||437.5||1300||1650|
|.33 cal 00 buck||437.5||8||48.5||1300||183|
|.090 cal #8 shot||437.5||397||1.1||1300||4|
Looking back at the formula for calculating kinetic energy, you'll notice that kinetic energy has a greater sensitivity to velocity as compared to mass. This is important because after the projectiles leave the muzzle of the shotgun, they encounter air resistance and begin to immediately slow down. We are going to talk a little more later on about some of the variables that effect how much a projectile decelerates when encountering resistance such as air or tissue; the important thing to grasp here is that as your projectiles travel downrange towards their target, they bleed off speed and therefore lose energy.
We've crunched some graphs to give you a general idea about how typical shotgun projectiles bleed energy travelling downrange as a result of air resistance:
Average kinetic energy/range of various foster slug loads.
Average kinetic energy/range of various buckshot loads.
Average kinetic energy/range of various birdshot loads.
Caution on Kinetic Energy
As previously mentionned, Duncan MacPherson writes in his highly respected scientific work "Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma" that Kinetic Energy is a dangerous and often misleading way to look at the relative "stopping power" of any given projectile. Again, the reason for this is that a large amount of the kinetic energy can be deposited performing work that does not cause tissue crushing. Examples of this type of work are thermal heating and displacement (stretching) of the tissue.
Recall from our quote of Mr MacPherson that stress (force per unit area) is the mechanism by which tissue is crushed, and the technical treatise that follows spells out a model of preducting wound trauma based primarily on sectional density, bullet profile, and bullet velocity. As most shotgun projectiles are spherical in nature, sectional density and velocity become the two important variables to consider when selecting a defensive shotgun load. We've already talked about velocity, so let's explore a little the concept of sectional density.
Sectional Density is the relationship between the overall mass of a projectile and it's cross sectional area. Mathematically it can be expressed as:
As most shotgun pellets are spherical in nature, there is a linear relationship between sectional density and pellet diameter. The following table illustrates the sectional density of a variety of different possible shotgun projectiles. The table also characterizes the difference between steel and lead shot of the same diameter; the sectional density of the lead shot is in all cases approximately 50% greater than that of it's steel counterpart. While we've never heard of anyone making steel buckshot, we've chosen to include the calculations for steel sectional density simply for interest's sake.
|Shot Size||Pellet Diameter
|.74 cal rifled slug||.740||438||NA||0.1166||NA|
We've taken the lead shot data presented in the above table and expressed it in a slightly more visual way with the following chart:
Sectional Density of Lead Spheres
What is interesting to note is the relatively poor sectional density of the 1 oz foster style slug. Often you will read stories about the "massive overpeneting potential" of these styled slugs...looking at the graph on sectional density you'll notice that the 1 oz 12 gauge slug does indeed have significantly more sectional density as compared to buckshot, but keep in mind that it's sectional density of 0.1166 is significantly less than that of a 50 or 55 grain .223 bullet you're likely to find fielded in many defensive carbines. Sectional density of larger caliber bullets is even greater (ie: 0.226 for a 150 grain .30 caliber bullet). Given these considerations, from the standpoint of overpenetration we feel that a 1oz slug equipped 12 gauge deployed in an urban environment is not nearly as dangerous as a centerfire carbine, expecially when considering the soft lead used in the construction of these slugs and their comparatively lower muzzle velocity.
Also interesting from the statistics above is the large caliber balls. While we are not aware of any of the major ammunition manufacturers currently including these loads in their offerings, they've been used for ages by handloaders. While not as accurate as the rifled slug offerings currently widely available, their increased sectional density (and concequently increased penetrating power) is what makes them interesting, particularly in a dangerous game application where the engagement range is anticipated to be close and significant wound trauma generating capability is required with the quick handling charracteristics of a shotgun.
When discussing velocity we briefly mentioned recoil; it is important enough however to warrant a small paragraph of its own. Let us re-iterate the key concept you need to understand about recoil; the 12 gauge shotgun is capable of generating more recoil than many people can effectively manage and there are costly consequences associated with doing so. The costs levied against overall tactical effectiveness are steep for many reasons and not only limited to flinch development, psychological fear of their weapon, reduced reaction time, and reduced capability to follow up if required. Excessive recoil should be avoided.
There are many reduced recoil loads available in both buck and slug loadings, and they are worth their weight in gold. Many people dismiss them summarily, either for falsely believing that they don't bring enough energy to the table to be effective in a tactical role or subscribing to the misleading "more energy is always better" school of thought. We've collected many actual "deer sized game" shooting examples and have posted some of them in our shotgun terminal ballistics article. These examples (which will be expanded over time) illustrate the significant wound trauma capabilities of these excellent loads.
We believe there is absolutely such a thing as too much energy for the job and, in our opinion, for many people the high mass/high velocity shotshells absolutely fall into this category. Choose something that you can shoot comfortably.
All this being said, there is some useful technical trivia on recoil worth exploring. Sir Isaac Newton was a 15th century physicist who is now famous for his three laws of motion. His second law is likely the one people are most familiar with, and it states that for every action, there is an equal and opposite reaction. So when the hammer falls and that shot column (with all that gas as well!) accellerates down the barrel, an equal amount of energy is imparted to the shotgun and the operator will feel this force in the form of recoil.
Newton mathematically expressed his famous law as:
where f = force (newtons), M = Mass (kg), and a = accelleration. What's interesting is the concept of mass...particularly that of the gun. Consequently, a heavier gun will recoil less than a heavier one. In the world of the shotgun where some loads are literally capable of knocking the shooter flat on their butt, this is not simply trivia. By increasing the weight of your shotgun you can effectively and significantly reduce the negative effects of recoil.; ie: given a constant recoil force the greater the mass of your gun the less it will accellerate backwards against your body. As such, if you've determined that you have an application for the 3 inch magnum bruisers, you might consider bolting on a side saddle or an extended magazine tube for reasons other than their advertised utility.
Now that we've got all this techical babble out of the way we're in a slightly more informed position to evaluate the tactical applicability of specific shotgun loads, starting with birdshot.
Birsdhot is typically a poor choice for deployment as a tactical load, owing primarily to it's poor sectional density. It bleeds velocity and energy quickly and as such has limited effectiveness at close range which rapidly erodes to zero effectiveness as range increases. Ironically, people often choose birdshot because of it's poor sectional density/penetrating capability. This choice is often made in consideration of a densely populated urban or family environment where the shotgun operators are concerned about collateral damage as a result of either building material penetration in the event of missed shots and overpenetration in the event of a good, solid hit on target.
The simple truth of the matter is that unless contact distances are involved (5 yards or less), most birdshot lacks the penetrating capability required to inflict meaningful wound trauma. Wounds from birdshot tend to be extremely gruesome, yet shallow. They often shred and destroy a large volume of tissue but don't penetrate deep enough to damage critical cardiovascular or CNS structures required for incapacitation. Clothing can further amplify these poor penetration characteristics.
While increasingly difficult to acquire as a result of being banned for waterfowl hunting, lead BB is likely the smallest shot we would elect to use in a tactical application. This choice would only be made in the densely populated family/urban environment mentionned above, and anyone making this choice would be wisely counciled to have more significant ammunition immediately available in the event that the lead BB does not produce the desired effect.
Buckshot has been the tactical load of choice for many, many years and has recently been subject to something of a revolution in terms of performance. Modern wad and buffer technology coupled with hardened, plated shot has decreased pattern size significantly and almost doubled the useful range of many buckshot loads.
Keep in mind that every shotgun/barrel combination patterns differently. Getting out and patterning your gun/barrel combination with the loads you intend on employing is likely the most important thing you will ever do with your shotgun.
While 00 buckshot is certainly the most popular, based on their internally generated minimum penetration criteria, Dr Martin Fakler and the IWBA suggest that #1 buckshot is a better balance of penetration, shot diameter, and pellet count. After conducting our own gelatin tests as well as tests on deer sized game, we tend to agree with them.
Shotgun slugs typically come in two varieties: those designed for smoothbore barrels and those designed for rifled barrels. The question often comes up concerning gun damage incurred by firing either rifled slugs in a rifled barrel or saboted slugs designed for rifled barrels in a smoothbore barrel. As a general rule, either slug cna be fired in either barrel without risk to health or property, however accuracy is greatly impacted by selecting the appropriate slug for the appropriate barrel.
Slugs designed for smoothbore barrels are generally of the traditional foster design, and have been subject to meaningful technological improvements over the years. One of these improvements has been the introduction of "rifling" to the geometry of the slug. It is a widely held misconception that these grooves function to impart stabalizing spin to the slug in the absence of rifling in the barrel. High speed motion photography has demonstrated that little to no meaningful spin is imparted to these slugs when fired in a smoothbore gun, however the grooves do serve a purpose in significantly reducing lead fouling in the barrel of the gun, especially when the slug is swaged somewhat through a choke.
Foster style slugs are available in a mind boggling array of different configurations from just about every ammunition manufacturer in North America. Most of them are manufactured from soft lead, however some such as the Brenneke brand are made from alloyed lead and as such are significantly harder. This is meaningful, for one observation we made while conduction our gelatin testing on various 12 gauge rifled slugs was that when the softer lead slugs are pushed faster (or more appropriately, when they hit the target media at velocities higher than about 1200 fps), they deform/break apart such that their overall penetration is restricted. At lower velocities they deform much less and consequently enjoy deeper penetration. Brenneke's slugs, not subject to the extreme deformation as their softer foster counterparts, are capable of being pushed much faster while retaining superior penetration potential.
Foster style slugs tend to rely on a "mass forward" principle to stabilize them both in flight and as they travel through target media.
Slugs designed for rifled barrels tend to be primarily saboted. These slugs typically require the spin imparted by the barrel's rifling to stabilize their flight and tend to fly with wild erraticism when fired in smoothbore guns. However, when fired through a rifled barrel, they often exhibit superior accuracy and can be accurately shot out past 150 to 175 yards as compared to their smoothbore cousins that aren't much use past approximately 100 to 150 yards. As with everything there is a tradeoff though...a shotgun equipped with a rifled barrel is a specialized tool in that it is only useful for shooting slugs. Shot spun by the rifling disperses at such an extraordinary rate as to be of little to no use even at close range.
To be continued...