Shotgun Ballistics

Shotgun BallisticsThis article answers a reader’s question and discusses shotgun ballistics.

“What about Shotguns and Shotgun Ballistics? The entire Ballistics Series was great and it was the first time that the science behind shooting was explained in a way that made sense. I’m considering a shotgun for home defense, so could you cover Shotgun Ballistics in one of your upcoming articles? Thank you.” – Brian in Temecula

Brian, thank you for the e-mail and for the opportunity to give the venerable shotgun the attention it deserves. Although there are many similarities between shotgun ballistics and rifle/pistol ballistics, the differences are significant enough to focus solely on the shotgun. What makes shotguns unique among other firearms is the wide variety of projectiles that can be fired from the same platform. This includes everything from a slug and a sabot round through buck shot, bird shot, and a number of less-than-lethal options. Since slugs and sabot projectiles are single solid projectiles, their ballistic characteristics are very similar to the pistol and rifle projectiles covered in the Ballistics Series. Therefore, I will focus the majority of this article on buckshot and birdshot.

Internal Ballistics

If you recall, our discussion on internal ballistics focused on the characteristics of the firearm, the cartridge, and the initial actions in the firing sequence that occur within the confines of the firearm. For this discussion, we’ll start with the cartridges, known as shot shells, and their components :

shotgun shell case cutawayPrimer – similar to rifles and pistols, the shot shell primer is a small metal cup that contains an explosive mixture that, when struck by the firing pin, sends a small flame through the base to ignite the propellant.

Base – brass, steel, or aluminum, the base is a multi-function element that houses the primer, binds the hull, and provides rigidity to interact with the extractor and ejector to ensure firearm function.

Hull – polymer, plastic, or paper, the hull ensures the proper functioning of the shot shell by holding the individual components together behind a crimp. Once the propellant is ignited, the hull expands to the diameter of the chamber and ensures a sufficient gas seal to send the wad and shot forward.

Propellant – similar to rifles and pistols, the propellant, once ignited, produces the gas expansion required to fire the projectile(s).

Wad – Different from rifles and pistols, a shot shell requires a wad in order to: (1) provide a small internal compartment to contain the propellant and keep it separate from the shot or projectile; and (2) provide a buffer that absorbs shock and minimizes deformation of the shot as it accelerates from rest to initial velocity.

Shot – From a collection of very small to large lead or steel pellets through slugs, sabots, or less-than-lethal projectiles, the shot is a single or group of projectiles delivered from the firearm to the target.

Gauge and Chamber

shotgun-gaugeWhereas rifles and pistols are designated by the caliber of the projectiles they fire, shotguns are designated by the shotshell gauge. While most shooters have heard the common gauges of 12, 20, 28, and .410, few know the origin of the term. A shotgun’s gauge is determined by the number of round projectiles of equal diameter that can be subdivided from one pound of lead. For example, a 12-gauge barrel was designed around the fact that one pound of lead could be divided into twelve 0.727-inch lead balls. The same methodology is true from the 4 gauge down to the 28 gauge. .410 is the exception to the rule since it was simply a determination of the diameter of the bore in fractions of an inch.

While the gauge determines the inside diameter of the bore, the chamber designation determines the maximum length of the cartridge. Most shotguns can chamber a cartridge of either 2-3/4 inches or 3 inches while others can handle a 3-1.2 inch shell. Together, the gauge and chamber determine the maximum volume of shot or size of the projectile.


Whether lead, steel, or another material, the shot is a volume of small diameter round projectiles. In the preceding section, we discussed how the gauge and chamber determine the maximum volume of shot a cartridge can contain, the diameter of the shot itself will determine how many projectiles can fill that volume. Ranging from #12 shot (at 0.05 inches per ball) to OOO, or triple-ought (at .36 inches per ball), each have their own application. Skeet shooters engaging fast-crossing targets at close range desire a large quantity of small pellets, so they typically choose a #9 shot. Conversely, trapshooters engage targets moving quickly away from the shooting position, so they choose either a #8 or a #7.5 shot with the requisite momentum to catch-up to and break the clay pigeon. The smaller shot is ideal for breaking clay pigeons or taking-down game birds without destroying their feathers or meat, but the small shot retains insufficient energy to take-down a larger game animal or subdue a felon. In these cases, the larger buckshot, slug, or sabot is chosen.

Internal/External Ballistics – Smooth-Bore, Forcing Cone, and Chokes

Break-open, pump, and semi-automatic shotguns share the same cycle of operations and functions as the rifles and pistols I covered in Internal Ballistics – Part I. Very briefly, as the firing pin strikes the primer, a small flame is sent through the base and into the hull, which ignites the propellant. The resulting rapid gas expansion pushes the plastic hull against the inside of the chamber causing a seal from which the wad and its contents can only push forward down the bore.

Shotguns, however, differ from pistols in rifles in three main areas: smooth-bore, forcing cone, and chokes. While some shotguns are manufactured with rifled bores, many more are manufactured with smooth bores. The rifled bore is designed primarily for the rifled slug and sabot rounds and produces the gyroscopic stability required to send the projectile to the intended target. Technically, birdshot and buckshot can be fired through a rifled bore, but the rifling will “spin” the plastic wad which will translate the centrifugal force to the shot and open the shot column into a “V,” leaving a large gap in the center of the shot spread. Therefore, birdshot and buckshot are meant to be fired through smooth-bores.

Since the chamber is larger than the bore, something needs to gradually “step-down” from the hull diameter to the inside diameter of the bore. This is the forcing cone. The length and shape of the forcing cone will affect the efficiency of the wad and shot traversing the length of the barrel. Too-short of a forcing cone can exert undue stress on the lead shot and cause deformation while too-long of a forcing cone may not generate enough pressure for sufficient initial velocity.

Once the wad and the shot exit the barrel, the volume of shot expands in both length and width. The size of the shot, shape of the forcing cone, and constriction provided by the choke work together and determine how much the shot column spreads as it travels down-range. As this shot column passes through a two-dimensional plane at any distance, it leaves a pattern. The following graphic demonstrates the spread of the shot pattern at different distances…. Read more >>

Posted by Howard Hall


Which Shotgun to buy with a Best Fit, Function and Finance Considerations

Which Shotgun to buyYou now have decided to dive into the opinion filled world of which kind of shotgun to buy. Like all firearms purchases, you need to be able to make an informed decision that suits your needs. Just like pistols and carbines, the three important factors are FIT, FUNCTION, and FINANCE. Once you have answered these questions, other factors such as accessories and looks can be left to your personal preferences. As shotguns can be used for home defense and sport shooting and hunting, there is long list of variations to suit each need. For this articles purpose I will stick to which shotguns you should buy for home defense.


There are up to two main points when it comes to fitting a shotgun. The first is the distance to the trigger from the butt stock. This distance is important, as you must be able to place the toe or bottom part of the butt stock into the shoulder while your finger can easily rest on the trigger. If this distance is too far you will always feel like you are stretching out and it will not be comfortable holding it, much less shooting it! The ability to mount the shotgun high up into the shoulder firmly and lean into it is essential to managing recoil.

The second is the ability to establish a good grip on the fore end or “pump”. Now if the shotgun is a semi-auto or other than a pump action, the placement of the front hand is simply in a place that you can manage the gun. For pump action guns you need to be able to “run” the action fully. This means pull the action all the way to the rear and all the way forward without short stroking it. Pump action shotguns need to be cycled to function properly and most malfunctions are induced from “shorting” the action.

For young teens and smaller people such as petite women, finding a shotgun with a Youth Model 13″ length stock is a good buy. Generally a 14″ stock is standard for most 12 and 20 gauge shotguns. A quick way to check is to rest the stock of the gun in the bend of your elbow, if your hand can maintain control of the grip and reach the trigger you can manage the shotgun. For the fore end, if you have trouble reaching and pulling the action to the rear or issues pushing it completely forward while in your shoulder, a extended fore end is a good choice. With My T-Rex arms, I can tell you a shortened stock and extended fore grip make the experience much better. A barrel length about 18 to 24 inches is more than enough, any longer and your looking at a gun great for clay shooting and birds, but terrible for moving through a hallway.

As far as the position of the safeties, action release or shell trips, it comes down to preference. I have no idea why, but Mossberg should feel better to me, everything is in the right place, yet I seem to like Remington. If it feels right go with it.


For home defense you should go with a 12 or 20 gauge with a few features that make it suitable for your personal protection. There are many “tactical” shotguns readily available off the shelf, and when we get to finance you can decide what extra gadgets you want to add on. You want something that hits hard, is easy to use, simple in design and carries enough ammunition to get through a fight. Some of the factors you need to consider are:

Gauge is the diameter of the barrel. The smaller the gauge the larger the barrel.

The most common are 12 and 20 gauge and can fit most any purpose. The felt recoil of a 20 gauge is less than the 12, but both are similar in price and function, and as above, great for youth and some ladies.

Action is the operating system for a shotgun and can be broken down into three groups. Pump, semi-auto and double barrel.

Pump action shotguns are the most popular of the three, they are simple to use, yet need practice and proper fit to be used effectively. Most malfunctions are induced by improperly cycling the action, and can be physically demanding.

Semi-automatic shotguns make you want to spend the money. They work by recoil action and with Semi Auto Shotgun the proper ammunition run smooth fast and cause less fatigue. However, malfunctions are slightly harder to clear.

Double barrels are generally break action where the barrels tip open to load and unload. They are very reliable, but have a low ammunition capacity.

Magazine Capacity: Most semi automatics and all pump shotguns use a magazine tube. Buying a model with, or adding on an extended mag tube is a great option. Many standard shotguns come with a 3 or 4 round magazine tube; I prefer having at least 5, plus one more in the chamber. Just remember more shells equal more weight.

Choke is a four-inch tube that screws into the front of your barrel that tightens the pattern of the shot. For home defense, “cylinder bore” or no choke will suffice when using buckshot. However, buying a shotgun that has the threading to change out the choke will give it versatility for hunting or sport reasons, just keep in mind that slug rounds will not fire through several types of choke!

Sights, rails, muzzle breaks and pistol grips all are personal preference. I will say that the type of front sight is important, as it needs to be visible and easily acquired. A high visibility dot or fiber optic works great, and suits the home defense purpose. For the rear sight you can go with nothing at all, or one of the various designs available. I really don’t like a rear sight, it is a shotgun after all, but many people like circular peep sights similar to a rifle sight. Rails allow you to mount optics and more importantly, a flashlight to the shotgun and for home defense a flashlight is an excellent tool. Optics such as a red dot sight can make target acquisition fast, but you have to compare the cost to the possibility of speed. As far as muzzle breaks, they are designed for breaching doors, and most owners can due without. You will either love or hate pistol grips, some shooters swear by them, and yes they look very cool, but I can’t draw any definite conclusions that they reduce recoil or make it easier to aim in.


One of the best reasons to buy a shotgun is they are cost effective. A good off the shelf pump action Remington or Mossberg will cost you between $400 and $600. A Benelli semi-auto will cost $1200 or more, with Mossberg and Remington not far behind. You get Benelli Supernova what you pay for with all three, but I have yet to hear a Benelli owner complain and I would steal Chris Whites M2 if I could get away with it. It is a safe bet to go with a Mossberg 590 or a Remington 870 for a pump action and a Benelli for semi-auto. I was pleasantly surprised at Benelli’s Super Nova pump action after one of our clients brought it to a course and I considered buying one, but went with a Remington 887 instead and loved it.

Shotguns are simple reliable tools, and do not need to be fancy to be effective. My best advice would be to go simple and bare bones, have a good front sight, an extended mag tube and a way to mount a light. After all that it is all fluff. When things go bump in the night, all the super cool gadgets will not make you any more effective. Shop around, ask questions and read Chris White’s articles on how to customize your shotgun without breaking the bank. With knowledge and common sense choosing which shotgun to buy will become easy.


Posted by Aegis Academy Staff.

History of the Shotgun from its Beginning to Present Day Uses

History of the ShotgunThe history of the shotgun is a trip through time. The shotgun has been called many different names and has had a variety of uses, both in military and civilian hands. Arguably, it is the most versatile weapon invented in the modern age of warfare. The weapon has had many names over the last few centuries, such as Blunderbuss, Fowling Piece, Scattergun, Trench-gun and in modern time, the Shotgun. Let’s take a look at the history of the shotgun, how it progressed from the 1600’s to today and how it became the weapon/tool we see utilized around the world.

Similar to many things that shoot hot lead, the Germans were the first culture to use a ‘shotgun.’ In the 1600s they designed a weapon called a ‘blunderbuss’ a short musket loaded from the muzzle and fired from the shoulder. This same type of weapon became a ‘fowling piece’ in the 1700s used by the British to hunt large birds with what we now call ‘birdshot.’ In 1776 the term shotgun was first used in Kentucky to differentiate between a ‘smoothbore shotgun’ and a rifled ‘musket’.

During the Civil War, cavalry units favored the shotgun for moving targets and close range work. Right after the Civil War and during the Indian Wars, Americans began the movement west to settle the vast open terrain that is now referred to as the infamous ‘Wild West.’ This was a time and place where nearly everyone had a shotgun due to the versatility and effectiveness of this weapon!

One significant technological advancement in the history of the shotgun occurred with the invention of the double-barrel shotgun in 1875. It was now a breach loaded, side-by-side or over under weapon used with a purpose built shell or cartridge with shot or pellets. This portion of American history is where the term ‘riding shotgun’ and ‘coach gun’ were first used. The term was used for the coach riders who provided security for the strongboxes transported by stagecoaches and trains. Coach riders and lawmen both favored the double-barrel shotgun. It was short and easy to use with devastating results at close range. On a side note, Doc Holiday used a side-by-side double barrel ‘scattergun’ in his only accredited confirmed kill.

From 1887 to 1900 the history of the shotgun progressed as John Moses Browning designed the first lever action, pump action and auto loading shotguns. As with many of the weapons Browning designed, the shotguns of today are still the same basic design he invented more than 100 years ago. Sights and optics have moved forward, but the simple design of the pump action is used by all manufacturers and very little has been changed!

During World War I, the trench-gun was used for close quarter fighting in the enemy trench lines. Short in length, fitted with a heat shield and bayonet, it was extremely effective and reliable in the trenches when compared to the bolt-action rifles of that timeframe. In World War II, the Marines used pump-action shotguns to great effect in the caves and tunnel complexes in the Pacific Theatre. Again, the M-1 Garand was 43.5” long and weighed 11.6 pounds loaded. A shorter barrel length with buckshot proved to be more effective in the typically extreme close quarter engagements of the day.

During the Korean War the shotgun became the guard weapon of choice because of its great effectiveness at close range. The US Navy SEAL Teams used a modified ‘duck-bill’ shotgun for walking as a lookout in the thick jungles of Vietnam. The muzzle of the barrel had a side-cut type of choke system that would produce a horizontal pattern with devastating effects. The weapon of choice was a pump-action Ithaca 10 gauge with 00 buckshot, while the Remington 870 12 gauge was used with great effectiveness as well.

The history of the shotgun continued into urban terrains in the 1980s and beyond, and it became more than just a weapon. As a ballistic breaching tool it gave soldiers a quick, lightweight and effective way of opening doors, gates and anything else that obstructed the assault style of warfare that has become common in the last two decades. The military has now adopted the Benelli M-4 auto loader as the new shotgun of choice for combat units. Many other manufactures are experimenting with fully automatic shotguns with box magazines that hold up to 10 rounds.

The history of the shotgun will continue to add new chapters as new developments are made. Shotgun ammunition has also progressed along with the weapon, but that is a discussion for another time. While the shotgun may adapt, the utility of the weapon still makes it my favorite choice, and if for some strange reason I ever find myself with only one gun, I sincerely hope it is a shotgun!

Drive fast & take chances!

First Published at Aegis Academy

About Author

– Chris White

Range Master
Chris White, Aegis Academy, Firearms InstructorChris White is 20-year veteran of the United States Navy (SEAL Teams) where he retired as a Chief (SO7). He has multiple combat tours and was assigned to three different SEAL teams as well as Naval Special Warfare Development Group during his active duty service. His key billets include: Assault Team leader, Platoon Chief and Platoon LPO at Development Group. He spent 6 years in instructor and training assignments during his career. Since his retirement, he has worked as an instructor and contracted operator at numerous high threat security providers in the Middle East and Africa. He continues to deploy in support of contingency operations and high threat protective details spending approximately 120 days a year overseas. He holds an extensive list of Department of Defense and Special Operations Command certifications and qualifications.