Weapon Systems: The Martial Virtues of the Pump Shotgun

The pump action shotgun has remained largely unaltered in concept since its introduction in the late 1800's. Even vintage pump shotguns still effectively compete with modern semiautomatic designs. To understand why this design has endured so long and appears to fulfill an archetypical martial expression, it's important to understand the roles it serves and the history of its evolution.

Background

The continued existence of the modest pump shotgun as a viable option when semiautomatic rifles are now economically available for comparable prices can help provide some clues as to which advantages are unique to the shotgun alone. The shotgun in historical context is essentially the contemporary progeny of the musket, and it shares many of the same advantages and disadvantages of its ancestor when compared to a rifle. Advantages of the musket upon its introduction were the devastating effect of a musket load relative to handgun rounds, a durable design, a simple method of operation, and with lead shot composed of many projectiles, a high probability of hitting a human target per trigger pull. Disadvantages included slow reloading, cumbersome size, perpetually inaccurate projectiles, the weight of the weapon, and the large, ballistically inefficient projectiles historically necessary for effective terminal performance. As technology in metallurgy advanced, inventors began to eliminate certain disadvantages of muskets which caused longarm development to diverge into 2 specializations: simple shotguns and precision rifles.

Rifles sought to improve on the musket by improving precision of barrels and replacing large, slow projectiles with small, fast projectiles exhibiting more efficient ballistics. These advantages entailed certain disadvantages, however. Rifles are more expensive to produce than a shotgun of the same size due to the precision of the barrels and components. They also require more intensive maintenance, configuration, and cleaning to ensure performance to a precise standard, which can degrade with neglect. They are much more complex than the muskets they replaced and can be less durable in consequence. Further, the ammunition is also more expensive and must be loaded to especially strict specifications in order to fire safely, effectively, and consistently which can render the shooter dependent upon industrial production. To configure a rifle and ammunition additionally requires intensive measurement and adjustment. Achieving good hit probability per trigger pull then requires intensive training and further precise adjustments. Even when a rifleman has learned these skills they still need to learn combat tactics which are not addressed in the least by rifle maintenance and accuracy training alone.

The shotgun developed to serve different priorities and a different philosophy of combat. Rather than improving on accuracy and precision, shotguns attempted to fully realize the advantages of the musket (simplicity of construction and operation, reliability, durability, devastating effect, and good hit probability with multiple projectiles) while eliminating certain disadvantages (weight, size, and slow reloading). What results is a firearm that is easy to use, effective, reasonably quick to reload, cheap, simple, durable, reliable, and resilient despite parts breakage.

Simplicity

The greatest virtue of the shotgun is its simplicity of design. Homemade shotguns can be made with a shotgun shell, a 3/4" steel tube, a 1" steel tube, an endcap, a washer, a sharpened screw, and JB Weld. (Another reason why gun control is impossible). The pump action shotgun is merely a refinement of those core elements. The 3/4" tube is equivalent to a makeshift barrel, the 1" tube and endcap is a minimalist bolt and chamber, the screw is a primitive firing pin assembly. Stock, grip, and bead sight are optional additions that make the homemade gun comparable in functionality and identical in lethality to any single shot 12 gauge. This minimalism of assembly lends well to user serviceability. Even the ammunition is a standardized kind of musket load contained in a plastic shell. In fact, in situations where shells are not attainable, but lead, cloth, and powder are available, a shooter can still reseat a primer on a used shotgun shell and muzzle load a contemporary shotgun with powder and lead shot to yield a makeshift musket with equal power to a regular 12 gauge shell. Finally, the operation of the shotgun is simple. Press the slide release, pull and push the slide, sight the bead at the center of the target, and pull the trigger. The simplicity of function additionally expands the tolerances of the gun for error. A slightly misaligned bead sight is equally as accurate as a zeroed bead when using buckshot. This means a shooter in combat conditions can knock a bead sight out of alignment or even knock it off the barrel without losing combat effective accuracy. Underpowered shells that would fail to cycle in a semi auto can also be manually ejected by the pump which makes a well made pump action less finicky about functioning with a variety of ammunition. The gun can potentially work as well for a novice as an expert, which reduces the degree of skill necessary for combat effectiveness, thus saving time for a vigilant civilian with priorities beyond preparing for war, which uniquely qualifies the shotgun as an easily wielded weapon by those with minimal training for tasks like perimeter defense in a civil emergency.

Even the names of the ammo indicate simplicity of purpose! Birdshot kills a bird in one shot. Buckshot kills deer sized quarry in one shot. Brenneke and magnum hardcast slugs kill just about anything short of an elephant... and designing an effective 12 gauge elephant slug is certainly within the realm of possibility provided there are hunters willing to fire one within 50 yards of quarry that large! By comparison, rifle and handgun calibers are subject to endless debates concerning the best caliber to use loaded to what specifications for how many shots to incapacitate a human threat. Shotgun logic is simpler. Shoot 9 pellet 2 3/4” 00 buckshot at human threats. One shot within 50 yards is almost always sufficient to stop any human threat. Repeat in the rare instance another shot is required.

Reliability

Pump action shotguns almost require purposeful mistreatment by the user to induce a malfunction. In place of precision, shotgun manufacturers have emphasized durability, especially in shotguns of the pre-polymer era. There are still police departments and military branches issuing perfectly functional steel and wood shotguns from the 70's and 80's with much less intensive maintenance than that required to refurbish a rifle. These are great weapons when one values reliability over precision and ammo capacity in situations where only one shot will likely be needed to resolve a threat. A similar justification might be used when selecting a revolver over a semi-auto handgun to avoid malfunctions.

In the rare instances malfunctions do occur, pump shotguns are also resilient and modular in their operation, capable of maintaining operation even with multiple parts broken or removed. If the magazine tube is broken or jammed, single shots can be loaded nearly as quickly as working the pump with some practice. If the shell elevator malfunctions, shells can be loaded directly into the barrel. If the extractor breaks, shells can be pried out of the barrel with the edge of a pocket knife. If the ejector breaks, shells can be removed by racking the slide back and manually prying the shells out of the action with one's finger. As mentioned before, if new shotgun shells are unattainable, the plastic on used shells can be cut off the brass and discarded, the primer can be replaced in the brass hull then loaded into the barrel and chambered, then powder, patches and shot can be muzzle loaded with a ram rod to yield a fireable musket for hunting or defense, even in cases where all the malfunctions mentioned have occurred simultaneously.

Durability/Longevity

The simplicity of components contribute to the durability of pump shotguns by reducing the complexity and fragility of specific parts, but the pressures contained and directed by a shotgun are also significantly less than those of a rifle or even a typical handgun. The maximum piezo pressure limit for the diminutive 9 mm handgun cartridge for example is 35,000 psi: 3x greater than the 11,500 psi limit recommended for 12 gauge shotshells. Less pressure means less noise per shot as well as potentially less wear on pressure directing components like barrels, bolts, and slide locks. Considering that these parts are usually overbuilt in most pump shotguns, longevity tends to be an intrinsic attribute of these guns.

Devastating effect

This trait of the 12 gauge appears indisputable based on cursory observation of shotgun fodder. The 12 gauge 'removes meat and bone' at close range, decimates a torso with multiple messy wounds, and can implode a human head with nightmarish results.

However, when considering the ballistics of 00 buckshot, the standard load for human combatants, the effectiveness of a shotgun is less obvious and more paradoxical. Even though many pellets delivered at once can be devastating, a single pellet of 00 buckshot is nearly a ballistic twin to the meager .32 acp handgun cartridge, conveying about 180 foot pounds of energy, or about half the energy of a mild 9 mm cartridge. It also seems this limited power per pellet may be unresolvable. Loading a shell to fire pellets more than 1,300 feet per second increases the power of each, but also reduces hit probability by increasing the spread of shot. However, this modesty of performance per pellet may have certain advantages in instances where one desires minimal risk of collateral damage at range. 00 buckshot retains lethal effect only to about 400 feet away due to the wiffle ball ballistics of the imperfectly round pellets deforming against one another through the barrel. A 00 buckshot pellet fired to 400 feet conveys less than 50 foot pounds of energy. It loses over half the energy it carried at the barrel and becomes essentially nonlethal.

So, how is a regular load of 9 pellet 00 buckshot within 15 yards so unquestionably devastating to human targets to the point where even 9 shots of .32 acp seem incomparable?  This outcome may owe to the simultaneity with which the individual pellets are meant to hit the target. The hydrostatic shock theory posits that the stretching and displacement of tissue when shot can be an additional source of wound trauma. Rifles accomplish this effect through increased projectile velocity which creates enough energy to separate bodily tissues, but a massive amount of energy per shot is required (bullet speed of 1,800-2,000 fps minimum for a human target, depending on who you ask). Shotguns may be the cheapest, simplest way to accomplish a type of hydrostatic shock by compromising the integrity of the tissues struck instead of increasing the power and speed of individual projectiles. While pellets fired one at a time will create separate wound tracks that close before the next pellet hits, pellets fired all at once result in pellets hitting tissues while they are already stretched and compromised. This further tears and displaces tissue resulting in essentially one giant wound that does not close because the elasticity of the tissue itself has been destroyed. This process may be directly opposite to the effect of a rifle round. A high energy rifle round increases intrasomatic pressure to the point that surrounding structures are damaged through overpressure. Buckshot compromises structures to the point that bodily fluids are under-pressured to sustain the organism. Both effects are greater than the sum of energies of individual projectiles in motion.

Only slugs are able to maintain suitable performance at range, exceed 1,400 feet per second at the barrel, and quite possibly induce hydrostatic shock with a single round, although according to Chuck Hawks, they "combine decreased accuracy, low velocity, low sectional density, low ballistic coefficient, rainbow trajectory, and heavy recoil." They perform about as well as musket balls, except they don't penetrate as well, which means only boutique hardened slugs with improved sectional density are applicable for large game or predator defense. In other words, just as a handgun is used to fight your way to a shotgun, a slug gun should be used primarily to fight your way to a rifle, or in instances where practicality, economics, or legality constrain one to use only a shotgun in situations where a rifle would be more effective.

Great Hit Probability

Though the most devastating effect of shotguns is delivered at close ranges, shotguns with buckshot still have merits at intermediate ranges (50 yards, or across a small field). Even with the advent of submachine guns capable of burst fire, pump shotguns are still able to fire more lead downrange in less time. Given the .32 acp as a fair comparison to a pellet of 00 buckshot, a single shotshell of 9 pellet 00 buckshot is equivalent in its combat impact to a 9 round burst from a .32 acp submachine gun. It can pepper and suppress a group of combatants, injuring some and forcing others behind cover. Shotguns also have perhaps the best hit probability per trigger pull compared to rifles, submachine guns, and pistols at 50 yards. At least 1 pellet out of 9-12 per shot is likely to impact a combatant at that range, which means at least one combatant injured or even killed per trigger pull. When one considers the effect of multiple scatter shots in succession, the shotgun can effectively suppress, injure, demoralize, and thin the ranks of a large group of assaulting fighters in very few shots given the element of surprise. This earned the pump shotgun the name 'riot gun' for this reason. The shotgun excels at perimeter defense and repelling a group attack. A great gun for 'social work.' For those assailants who do manage to close distance, the effect of buckshot at point blank range is almost guaranteed to be lethally gruesome, which can help to further discourage combatants not already struck by multiple projectiles as they advance.

For this reason, a perimeter shotgun loaded with slugs for stopping opponents at distance followed by buckshot for suppression is an outstanding defense. Due to the advanced firing rate possible, a single pump gun essentially duplicates the effect of several musketeers from centuries past, many of whom historically loaded buckshot for increased hit probability per shot.

For all the reasons described, the pump shotgun remains a common weapon a century after its development. It isn't precise, fancy, or efficient. It doesn't need to be. The fact it reliably suppresses or neutralizes combatants with very few trigger pulls is merit enough to recommend it still.