Self-defense inside the home: Avoiding over-penetration

Decisions, decisions, decisions… it seems like when it comes to defending your family there is a lot of them. Caliber, type, make, model, ammunition, stopping power, capacity, training, and the omnipresent legal repercussions—self-defense is a hailstorm of life or death choices and another one of these (and one that is often neglected) is over-penetration.

Shooting through walls

Situation and terrain determine tactics and nowhere is this more evident than when firing a gun inside a closed environment like your home. Accordingly, a self-defense minded gun owner needs to first take into account where he lives (suburban house, farm, studio apartment etc.) and then assess the location and materials used in its construction. These factors will help determine your choice of gun and round you keep for home defense.

Factoring in location and terrain means knowing where targets will appear, potential backstops and beyond them. Since most inner walls in homes in western societies are made of sheet rock and many outer walls made of brick or siding, it’s important to realize rounds could leave your home and keep traveling. Thinner than usual walls, glass windows or close neighbors should all play a part in your assessment of your home as should the sometimes strange angles and backstops inherent to ranch style or multi-level homes.

Remember, firefights are dynamic with people moving about helter skelter and this may include your children, so it is important to be aware of the location of spots where over-penetration can: a) occur and b) injure a friendly target. Practice identifying these places with your family with both the lights on and off; most home invasions occur during the daytime, but they also happen in the early morning and evening too. This underlines the importance of knowing and remembering your backstops and beyond.

Bullet type and caliber

Is bigger better when it comes to self defense ammunition?  I think that even novices would agree that it depends on if bigger is appropriate. So, how do you know what’s appropriate? Well, in a nutshell, by understanding the round/guns’ ballistic profile.


9mm (especially ball or target ammunition) can penetrate many layers of drywall.

Ballistics is the study of projectiles and represents a discipline in shooting that can quickly turn into a private obsession creating scientists out of hobbyists. Indeed, understanding the ballistics of a round is the key to understanding the theory of shooting—but realize that theory is not practice and you don’t need an intimate knowledge of muzzle velocity and “knock down” power to make informed decisions about over-penetration.

Despite the popularity of the round, too few realize that 9mm ball ammo can easily punch through not just one but several interior walls. By contrast, .223 rifle ammunition tends to tumble, turn and slow down when penetrating barriers, even more than a 9mm fired from some pistols. Many shooters like to debate this point, and admittedly on the surface it doesn’t seem logical, but studies done by SWAT teams over a decade ago revealed this phenomenon to be fact and it was one of the main reasons a lot of tactical teams transitioned to M-4s/AR-15s and gave up the H&K MP-5 SMG in the 80s and 90s.

Speaking of SWAT teams, while most have gone to ARs, one big city team in has stayed with the 12-gauge as have most militaries around the world which says something to me about the effectiveness of shotguns. Using rifle slugs and/or 00 buck, a shotgun allows both for powerful stopping advantage and light penetration.

But I’m also hesitant to endorse shotguns as the universal cure all for home invaders as Vice President Biden recently suggested. A shotgun blast is not like the movies where people fly backwards or fall down right away. One shot doesn’t necessarily mean one kill. Consider that your home invader may be high on PCPor some other drug. Tweaked out criminals can take a handgun round and keep going so take the time on the range to feel confident that you know what it is going to take to stop a human, which may mean a couple of shots.

There are also all kinds of handgun rounds out there—frangible rounds for instance—that promise to minimize penetration, mostly through projectile design.  This may well be, but remember over penetration with any type of ammo is a reality that cannot be ignored.

Tactics in the home

The key to defending your home and limiting penetration is to establish a point of domination. Assess your home and determine the likely entry points (mostly doors,


Always observe windows when assessing your home for a tactical advantage.

including the garage and sliding glass doors, and perhaps windows). From there determine a counterstrike strategy. Essentially, this means asking yourself, “Where’s the best location to fight from?” The best options are quality cover and concealment, good fields of fire, and excellent observation. On multilevel homes, high ground is preferred, especially when it gives a tactical advantage.

You also have to factor in how fast you can get to your weapon and get set up, covering the likely entry points of your home.  Realize that anywhere along the path to those weapons could turn into a battle zone. This is taking into account Murphy’s Law—you may have to fight from anywhere in your home, so consider observation, obstacles, and the other stuff mentioned above (e.g. fields of fire, cover and concealment) from less advantageous vantage points.

Weapons handling

If the entry point in relation to the key living areas is really small (like in a studio apartment), the size of the gun will matter—big time. So, which gun should you pull? Will there be enough time? And what does it mean for penetration?


With buckshot, over-penetration is not a genuine concern. Chambering a round in a 12-gauge gives off a distinct noise however, that stirs much debate in the tactical community. Hopefully, home invaders will turn and run when they realize you have a firearm, but hope is not a good tactic and shouldn’t be relied upon, especially because, if it does not work, it will reveal your position. This could lead your attacker to change his or her attack plan which may change your anticipated battle zone. (Really though, the better question is will there be enough time to “rack” a round?)


Like shotguns, rifles are long, though best used from a set position. Choose defense rounds that are of .223 caliber or smaller if you are worried about overpenetration.

When considering the time it takes to level a rifle at a home intruder and give a verbal command that you will use lethal force, I suggest you have a young, fast friend sprint from the door to where you keep your long gun. That demonstration will make you think about where to keep your gun, if you can get to it in time and where the round will likely be heading if it passes through its target.


By far, the quickest option in CQB is the handgun. Hollowpoints and other frangible rounds tend to separate and tangent in your target, while ball ammo will pass through the target and potentially beyond. Caliber size is less important if you use these types of projectiles, so I suggest using ammunition specifically designed for defense against humans. Like the rifle drill, it’s a good idea to have a friend run to your weapon location to see if there enough time to grab, turn, point, and shoot.

Location and storage of weapons

If you haven’t picked up on it by now, where you hide your gun(s) matters. When an attack is imminent, you need to get to a weapon immediately and you may not have time to run into the bedroom, the office, the basement, or wherever you store your gun to retrieve it.

defense weapon storage

If you have several self defense weapons, why store them all in the same place?

Just think about this for a second—how long does it take you to open your giant safe with a twisting combination number lock?

Logic therefore dictates that the best option is to have multiple guns stored throughout the house so you can access them rapidly and as the situation changes. Quick access safes, hidden and secure locks are important in these situations. With kids or grandkids visiting, no homeowner should take the risk of having curious or ignorant children hurting or killing themselves or others because they did not take the time to secure their weapons. That would be too tragic and criminal.

Using a lock on the trigger, a digital pad lock or a cord through the action, can keep the honest homeowner safe from accidents and tactically prepared. Education for kids is also needed but teenage kids should know how to protect themselves while their parents aren’t home. In the end, keeping several guns all over the house is certainly the best option for the average home.

Safety warning: Jeffrey Denning is a long time professional in the art of self-defense and any training methods or information he describes in his articles are intended to be put into practice only by serious shooters with proper training.  Please read, but do not attempt anything posted here without first seeking out proper training.

This article originally ran on as “Self-defense inside the Home: Avoiding Over-penetration” on 2/27/2015 and has been edited for content.

  • Aerindel Prime

    Sigh. Just when it seemed like had become readable again we get another little gem by Jeffery. Well, it was good while it lasted and I guess its an improvement to the site in general that its been at least a couple weeks since we where subjected to one of his opinion pieces.

    Over the past year or so I’ve been trying to determine if JD is a bad writer or just not very bright. The subject line this time would seem to indicate the latter. In standard JD fashion he starts out with a preposterous statement designed to generate ‘controversy’ (page views)

    Of course, as anyone who as studied the art of the gun at all should know, overpentration is a myth concocted by lawyers and makers of over-priced and underperforming ammunition. I think the FBI said it best in the seminal work “FBI Handgun wounding factors and effectiveness” when they wrote:

    “An issue that must be addressed is the fear of over penetration widely expressed on the part of law
    enforcement. The concern that a bullet would pass through the body of a subject and injure an innocent
    bystander is clearly exaggerated. Any review of law enforcement shootings will reveal that the great
    majority of shots fired by officers do not hit any subjects at all. It should be obvious that the relatively
    few shots that do hit a subject are not somehow more dangerous to bystanders than the shots that miss
    the subject entirely.”

    Yes indeed. It should be obvious, but sadly too many people learn ballistics from the marketing on the back of a box of hollow points.

    Reading on, things get slightly better. JD is actually correct when he says that 9mm (and indeed many pistol rounds) actually get more reliable penetration than high velocity, light weight projectiles. He even cites “studies” to prove it. Of course, once again, this is fake controversy since we have had lots of demonstrations of this on the internet over the past decade. The physics behind this are simple, if bullet construction is the equal, the energy involved the collision of a lead and copper slug at high velocities is more likely to cause the lead and copper to fragment and deform and be torn apart, shedding energy as it goes.

    But then again, we go down hill again when JD tries to tell us that entry teams have switched to .223 based weapons instead of 9mm submachine guns in order to limit penetration. Sigh. Of course you and I know that they did this because it was in the early 90’s that small carbine length AR type guns became available and that they are much more powerful and more available than the venerable MP5.

    Next he tells us how shotguns with buck shot provide high stopping power with light penetration. To say nothing of the fact that those two traits are mutually exclusive, its also simply not true. Anyone who has ever used the google knows that a 00 pellet actually penetrates a large number of drywall layers…and that even bird shot will blow through a couple interior walls.

    In reality, militaries and entry teams have kept the 12 gauge shotgun because of its ability to fire breaching rounds and LTL’s and because its a dang good weapon in close quarters.

    Next he starts talking about battle zones and the sound of a shotgun racking as a deterrent. Frankly, I don’t know what he is trying to say here other than his dangerously false assertion that shotguns do not penetrate.

    It actually all gets a little incoherent from here on. He rightfully states that it takes more time than you will probably have to get a gun out of a safe but then also says that guns need to be locked up to protect children. Well..yeah, I think we all know that. It sounds like he wants you to have a bunch of guns hidden and or locked up around the house. Not a terrible idea but he presents it in about the most cumbersome way possible.

    So in the end we are left with a bunch of patently and provably false information and some rambling about gun storage.

    Now, its not a total loss he does at least suggest you ask: ” Where’s the best location to fight from?” Which is something that people really should consider.

    All in all, an improvement over the typical JD article.

    • Saint_Barry

      It’s an improvement over “Open Carry vs. CC,” “Should I Use a Holster?”, or my favorite, “Is .380 Enough for EDC?”.

      • Aerindel Prime

        Agreed. This is actually a move in the right direction for JD, a very very small move.

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  • Pat N Shannon Dickinson

    I have been critical of some articles, but this one I think is a decent place to start a good discussion about the strengths, weaknesses, and needs of ones own situation.

    • Aerindel Prime

      That would be an interesting discussion to have. I for one wish someone in the gun world would address the issue of many of us relying on castle laws to defend homes that are essentially made out of cardboard and foam. I see a lot of people who spend thousands on guns but live in a house with giant indefensible windows and flimsy doors that anyone can just kick their way through. You really should treat your home like a castle, make it a defensible structure, make it a force multiplier that makes your one gun count for ten attackers rather than just using it as a place to have a gunfight.

      • Viper_002

        Exactly what place does “the gun world” play in residential building code? It say affordability of materials? Every ref or rebuttal you’ve given to op’s write up seems to be supported (by your own words) something you’ve searched on the Internet. Now, myself, as a REAL shooter, instructor, and an E6 NSW member for 10yrs can tell you that every single point JD made is valid and comes from legit science. Have you ever fired rounds into men while trying not to kill your friends sweeping the sides of the room or even next room over? Have you ever breached an exterior door with buckshot and examined the effects after? No I’m guessing you haven’t, unless we consider the vast amount of time you’ve spent playing COD. Until you yourself have been in a position to see how this stuff plays out in real time, I suggest you keep to what you know, which most certainly without a doubt is NOT firearms.

        • Aerindel Prime

          Its scary that your an instructor. Its also funny have these days COD seems to be the new nazis, as in every rebuttal on a gun website leads to someone bringing up COD as if its some kind of argument winner. Its also funny when people like to appeal to experience in a format where anyone can claim to be anything. We could talk about war stories or the times we where shot (well, I at least I could), for all you know I am a navy seal (i’m not) or a firefighter and EMT with extensive experience in forced entry, building construction, emergency medicine, command and triage (I am) who is only alive today because of the poor penetration of other people’s hollow point rounds. Perhaps you teach how to shoot guns in a range but I deal with the actual aftermath of shootings in the real world.

          But I would have no more reason to believe you than you would to believe me so rather than posturing on un-provable personal history lets stick to ballistics. Most of what JD says is scientifically inaccurate. That is a fact that anyone can test for themselves or look up data on.

          Building codes however are one of my favorite subjects, In simple terms, screw them. They are designed by banks to make houses easy to buy and sell and that is there only function. They neither make houses safe or cheap and should be just as offensive to freedom minded people as gun registration. In fact, many of the same players who want to restrict guns to only government officials are the same people that want to force everyone to only live in approved houses built by registered people.

          And just as gun owners must constantly find ways around gun control we should inform ourselves of ways to evade building codes. Myself, I chose to build my house in a place with no codes but even for people who don’t have the luxury there is a lot you can do to fortify your average cardboard doublewide and make it less of a death trap. Something as simple as functional shutters and steel door jams are not expensive and greatly improve your ability to defend your castle.

          When it comes down to your moment do you really want to engage on a one to one basis or do you want to be defending a fortified position?

  • Charlie Brown

    just use dum-dum bullets :)

  • Barry Hirsh

    Mr. Denning, with all due respect, if you don’t already have a gun on you, you have failed to meet the odds.

    Instead of stashing guns around the house in “quick-access safes”, one should home carry.


    Hell, I even carry when I go to the bathroom. If I’m taking a shower, the gun is in the med cabinet, sliding door open, a mere two feet from where I’m showering.

    Your article presumes that most won’t home carry. Instead of addressing “convenience” that accommodates this mindset, you should be encouraging being armed every minute of every day, anywhere you are.

    • Zack McMillan

      I agree with everything you said and I also carry everywhere around my home. I have an old Blackhawk serpa holster rigged out of sight to my bed. When I go to sleep I just click it in the holster. Locked in place with quick access.

  • JDon357

    While some detractors here make some valid points – I think the author knows who his likely audience is and what information will move them forward in a better direction at a reasonable pace. If you think of a statistical Bell Curve, within which sits all those who might read this article ranked by ‘experience and education’, he is not presuming to know more or to help those who are SPECOPS at one end of the spectrum – nor to open the eyes of those who are members of Mothers Demand Action (Bloomberg) at the low end of the spectrum, but to help the 90% that sit in the middle. If you have an efficiency apartment – no, you don’t need to stash guns in different places – one is enough. If you are a 90 lb. 60 year old, a shotgun might not be as logical as a .380. Articles like this are intended to get most of the people who read them to find a few pearls of wisdom and move them to thinking about One Improvement they can make to their personal defense.
    Not having read any of the author’s other articles, I cannot comment on whether this is better or worse.

  • 고등어

    What is the title of ‘ studies done by SWAT teams over a decade ago’?

  • Gil G

    How important are you if a firefight in your own house is a reasonable expectation to be prepared for? How about not selling drugs and/or not be a member of a criminal gang?

  • Dr. Ron Polland

    “With buckshot, over-penetration is not a genuine concern”

    Penetrating 7 or 8 walls might be a concern.


  • charlie baker

    Me, my bed companion is my S&W model 638 J frame, five shot 38 spl. It’s in an IWB holster right there under the covers with me, an inch away from my hand. That gun goes wherever I go in the house, within easy reach even when I’m showering. And I never leave home without it.

  • charlie baker

    Why no mention of Glaser rounds? I would think, all other factors considered, that Glasers would be safest in terms of terminating the attack, yet not over penetrating and endangering family members in other rooms, or neighbors in the next apartment. The very fact that we are discussing the danger of over penetration means we’re decent considerate people, who are willing to take on more of a risk to ourselves by using ammunition designed to be inherently less powerful to avoid harm to innocent people. Glasers would seem to be the happy medium. I just wish they weren’t so damned expensive.