Twenty-five years ago, “home invasion” was not a term that was widely used or recognized outside of law enforcement circles.

Today, that is not the case. A variety of threats face an increasing number of citizens. Furthermore, as Baby Boomers get older, physical issues may decrease their effectiveness with a firearm. Older, arthritic and less likely to have been exposed to firearms earlier in their lives, many of these law-abiding citizens have recognized that in the event of a criminal attack there will be a delay before police can respond. One positive change is that women are the fastest growing segment of gun owners. How best can Joe and Josephine Citizen defend themselves until professional help arrives?

One answer is the humble shotgun—versatile and reliable. But a 12-gauge slug has nearly the same energy at the muzzle as the 7.62 NATO cartridge. In short, it’s a big hammer. But for some, it’s too much gun to shoot comfortably. What are the alternatives? Thankfully, gun and ammunition manufacturers are recognizing the value of shotguns and ammunition for self-defense in loads other than the traditional 12—in particular the 20 gauge and .410 bore loads.

Can a bad guy tell the difference between being hit with a 12 gauge or a 20 gauge? It’s hard to find candidates to interview.

Deer have been compared to the average person in terms of body weight and effectiveness when it comes to shooting into living tissue, and the 20 gauge has certainly taken its fair share of venison.

Twenty-gauge ammunition is as versatile and easy to obtain as 12 gauge, and as the average age of the population increases, a short, handy 20 may be a great home defense gun for people with minor physical challenges that may prevent use of some other weapon such as a pistol or a 12 gauge.

If perception is a concern, in some circles, a simple 20 gauge may be perceived more as an innocuous sporting gun than, say an AR-15 or a Beretta 92. Another reason for exploring the use of a 20-gauge shotgun as a viable home defense gun is that most people can learn to shoot it quite well. The twenty loaded with either #3 or #2 buckshot (or even birdshot at very close range) may not overpenetrate walls to the same extent that a 12 gauge loaded with 000 buckshot may.

It may also be a suitable trunk gun for trips into the wide-open spaces where a longer shot may be required, and a quick change to a slug may be appropriate for self-defense.

Enhancing The 20

There is nothing wrong with a standard, sporting shotgun for self-defense—but with a few modifications, we can enhance its capabilities. This may not seem important until we realize that a self-defense incident with one or more violent criminals is a highly emotional, adrenaline pumping experience. Fine motor skills often go out the window, tunnel vision and auditory exclusion kick in, and events may seem to occur in slow motion. With all this going on, a simple, mild-shooting firearm that handles and shoots easily is a plus. I decided to build a self-defense shotgun that I could still enjoy using for informal trap shooting and hunting, simply by selecting appropriate ammunition and temporarily removing the flashlight.

I chose a Mossberg 500C pump action with a 22-inch vent rib barrel with removeable choke, bead front sight, standard 5-round tubular magazine, and wooden stock and forend. The physical dimensions of the receiver and barrel are smaller than the 500A 12-gauge version and the factory stock is slightly shorter to cater to the youth and female market. Stoked with slugs, it’s a good short-range deer gun. With birdshot, it busts clays to my satisfaction, and loaded with #3 buckshot it’s a great home defender.

However, there are some modifications that can be made to enhance the self-defense aspect while still retaining the recreational attributes. I could have chosen to only change one thing on the following list, and it would have been a step toward my goal. At a minimum, I would shorten the barrel and add a tritium front sight. Most of the following changes are not dependent on the rest, and the level of customization is up to the individual.

I recommend that all gunsmithing be carried out by a professional gunsmith. In my case, I asked my friend Bob Ford of Rocky Mountain Arms in Longmont, Colorado to make all the modifications.

Barrel, Sights & Rail

First, the Mossberg’s barrel was cut to 18.5 inches. The shortest length a shotgun barrel can legally be is 18 inches. Sensible gunsmiths will cut a barrel at 18.5 inches, just to be on the safe side. With the sporting bead front sight now gone from the muzzle, I opted to replace it with a Big Dot tritium sight from XS Sight Systems.

Next, the forcing cone at the chamber end of the barrel was smoothed out. This turns the chamber into a smooth funnel that reduces the amount of battering that individual buckshot get as they bump into each other on their trip down the barrel, and reduces the deformation of the comparatively soft lead shot. Deformed pellets cause wider shot patterns. Perfectly round pellets make for tighter shot patterns. This may not seem very important, but it is. Imagine launching a load of buckshot at a violent home-invader, only to have one pellet fly wide of the mark and hit that child standing on the other side of the street. In a defensive shotgun, effective range ends when the shot pattern is wide enough that some pellets miss the target.

A Picatinny rail was installed on top of the receiver using the existing screw holes. The rail allows for any type of optical sight such as a low-power scope or an electronic red dot sight to be installed. The advantage of these types of optical sights is that they allow for fast acquisition of the target/sight picture and can give better accuracy with slugs than the traditional bead sight. The rail I chose features a U-shape channel down the center of the sight that can be used as a rear sight.

Compact Thunder

With the work on the barrel completed, I still wanted to make the shotgun shorter so that it would be easier to manipulate through doorways and confined spaces, and to transport in a vehicle. I chose the side-folding stock with pistol grip from Choate Machine and Tool, which comes with a matching forend. (If you decide to order a Choate stock for a 20 gauge, call them and explain you want to adapt a 12-gauge forend and stock to a 20-gauge magazine and receiver and state the make and model of shotgun.) With the stock extended and tucked under the armpit, the pistol grip allows for one-handed operation of the gun, leaving the other hand to open doors or dial 911. Also, I wanted to add a Sidesaddle to the left side of the receiver to hold four spare rounds of ammunition. (On most pump action shotguns a shorter forend is required if a Sidesaddle is attached.)

The Choate replacement forend can be ordered with a short piece of Picatinny rail that allows a tactical flashlight to be attached. A flashlight is a very useful tool to add to a shotgun, but it’s important to understand how it fits into the tactics of home defense. The most important thing to remember with a weapon-mounted light is that wherever the light points, the muzzle is also pointing. Imagine hearing noises downstairs at 3 a.m. and lighting up a family member who is getting a drink of water in the kitchen! I took my SureFire 6P and secured it to the Picatinny rail on the forend with a one-inch diameter scope ring. Now, when my left hand is on the forend, I can activate the light with my thumb.

Finally, a sling swivel stud was installed on the barrel ring at the 9 o’clock position to work with the swivel mounted on the top of the folding stock. I added one of my favorite slings, a simple two point tactical sling from Specter Gear (#541 Universal Fit 2 Point Tactical Sling). A sling is to a longarm what a holster is to a pistol. It frees up the shooter’s hands without having to put the gun down. This is an important safety consideration because any time the gun is not under her control it may become a danger to others.

Be aware that every accessory—sidesaddle, light, sling, etc.—adds weight. While extra weight helps reduce recoil, it can also make the gun less manageable for some people. I’ve described the complete package, but if weight reduction were my primary concern, I’d first consider omitting the Sidesaddle and sling, and perhaps look for a smaller light or remove the light altogether.

For anyone contemplating having a shotgun for self-defense—learn the applicable laws; practice shooting with trap loads at first and then work up to shooting with whatever the chosen self-defense ammunition is; take tactical classes from professional instructors.

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Twenty-five years ago, “home invasion” was not a term that was widely used or…