over penetration in drywall?


December 7, 2004, 04:55 PM
We've all seen threads here about the best weapon for home defence. The question of over penetration keeps coming up with proponents of handgun, rifle, and shotgun all claiming the least penetration for misses. I decided to find out for myself how much of a problem it is.

I figured I would test common SD loads in 9, 45, 12 gauge, and 223 to see what did what. But I only got to the first step before encountering a problem. I wanted to get an idea of how much penetration there was so I could build a test fixture to simulate a series of walls. I set up eight pieces of drywall (four walls worth) with about two inches of seperation between them. I used a 124 gr. Gold Dot and it blew right through all of them. Not sure if it was expansion but the holes got bigger in each board.

So my question is what should be a reasonable standard? I live in a small to mid sized home, and it's hard to imagine a miss hitting three walls without leaving the house, much less four. I intend to put some sort of siding on the "outside" wall when tested, but how many walls should that be? Are missed shots destined to get out unless they hit studs, furniture, etc? And most importently, has anybody done enough testing to know what the results will be? I would hate to do this and have somebody point out some already existing source of the same data.

Thanks, Griz

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December 7, 2004, 05:20 PM
Back in July of this year I was involved in a case where a bunch doing a drive by shooting shot up a brick house with a pair of S&W .40 cal pistols.

The shooters out of about 20 rounds hit the house once, the round entered the house thru a small area of wood located between the front door and the brick, it made a slight left-hand turn just after entry striking a piece of furniture located just inside the door measured 20 inches from the point of entry, it shattered the flimsy wooden thing-a-ma-bob then hit a sheetrock wall dug about a 3.5 inch jagged hole as it made entry at an angle, exited the wall on the opposite side hitting a mirror on a big wooden dresser in the master bedroom. It continued to travel across the bedroom striking the far wall where it imbedded itself between the plywood and the outer brick of the home.

From best we could tell it was a normal run-of-the-mill .40 cal slug.

December 7, 2004, 06:24 PM
When I was young I had a ND with my Dad's 9mm. Bullet penetrated one wall, left a 12" or so gash in the ceiling then penetrated the exterior wall taking out a piece of slate siding the size of a baseball. It was ball ammo, unsure of the bullet weight.

I've wondered what would happen if someone fired a 44 mag in a mobile home park, the kind where the houses are about 20' apart and in straight rows. If the bullet did not hit a kitchen appliance or heavy piece of furnature, how many houses would it go through?

December 7, 2004, 07:21 PM
SISCO- You just described the mobile home park that I live in and one of my home defense weapons was a .44 Mag. I have always wondered what type of ammunition to use in that situation would be also, as caliber doesn't really seem to matter. My son was playing with his bow inside one day (35 lb.draw) and a target arrow went completely through the wall and outside. Luckily it angled down towards the ground. Last year the police tried to arrest a guy here for spousal abuse and he fled into the mobile home and began firing at the police with a shotgun and the police returned fire using .40 caliber handguns. No one behind the house said anything about their home having bullet holes in it but the guy threw gasoline on himself and the home and died in the fire. Maybe using what ammunition type the police use is the answer , I am not sure.

December 7, 2004, 07:24 PM
There's an older book about combat shotguns in which the author did tests of a number of types of housing walls.

He tested various sizes of shot, buckshot, and slugs on wallboard, plaster and lathe, and other common construction walls.

Bottom line according to his tests: No wall construction would stop any shotgun load except brick or cinder block exterior walls.

All shot sailed right through all interior walls, and all exterior walls except the brick or block.

Since most any bullet has better penetration than a shotgun, you can figure bullets will also sail on through.

December 7, 2004, 07:31 PM
I've seen a ND (I assume, it wasn't my house) go through 5 pieces of drywall (oblique angles) and an exterior wall within about 8 feet, so don't make assumptions about a small house.

For a thorough test, shoot through enough layers of drywall (or wood paneling: whatever is relevant) to completely stop the projectile. Personally, I would space them more like 4" or more.

Let's assume it took 24 layers total to stop. To check what might happen if it leaves the home, set up an exterior layer (metal siding?) after 6, 12, and 18 layers, in separate tests. You can duplicate or switch over to 1/4" plywood sheets if you find that the drywall doesn't have enough effect.

This should give you enough information to make educated predictions and comparisons.

December 7, 2004, 08:18 PM
I tried a redneck penetration test with military surplus 9mm full metal jacket. I stacked two by fours on each other and fired into them at short range. I found the bullet sticking out of the back side of the fifth two by four. Do not count on even a wall stud stopping a pistol bullet.

Maybe something to consider if you do ever have to shoot, is going to the floor to shoot, so you can shoot over your neighbors house? But,,, all bullets have to stop somewhere.

December 7, 2004, 09:24 PM
Im sure that even a .22LR would penitrate through a wall and be easily capable of injuring someone in the next room. I wouldnt be suprised if it penitrated out of the house. From experience, a .22LR will penitrate around 2 1/2 to 3 1/2 inches of hard wood from a rifle. That would be more than enough to penitrate several layers of drywall.

Unless you use frangibles (which will also penitrate wall pretty easily, but not as much as a JHP or FMJ), any bullet that misses can exit the house and continue on into another.

What do we all learn from this? Make your shots count! ;)

Instead of arguing all year which caliber and bullets design will work best, pick one, buy 1,000 rounds of ammo, and go to the range. Make sure to shoot in akward positions, since you never know where you will be shooting from if you ever do have to use your gun in SD.

Bartholomew Roberts
December 7, 2004, 09:28 PM
Here is a good thread from ARFCOM investigating that same issue (and with pics and follow-up tests as well):


Basically, the problem is that the only things that won't penetrate multiple layers of drywall (12 in the example shown above) also are totally ineffective at stopping a threat. In the above thread, even .22LR penetrates multiple interior walls with ease. The key safety issue is to not miss your target because the round is going to penetrate until it hits an exterior wall or some fairly sturdy furniture.

The second test (linked at the end of the above thread) includes a simulated exterior wall of pine boards and one layer of bricks. The exterior wall stopped all the rounds fired at it, though one of the 5.56mm and the 00 buckshot broke the bricks.

December 7, 2004, 10:32 PM
probably the same rounds the skymarshalls use would be your best bet, Glaser safety slugs.

Harry Tuttle
December 7, 2004, 11:38 PM
to reliably stop a human you need 15 inches of meat / bone penetration
(you need to account for a raised arm between you and a COM hit)


December 7, 2004, 11:51 PM
Hm... the .223 out of a rifle penetrates the least... interesting. I'd heard that somewhere else, IIRC.

December 8, 2004, 12:15 AM
I recently did some pistol testing myself, here's the results:

Cut up some 2x6" fir boards I had used as concrete forms several years ago for a penetration test and screwed them together.
The 7.62x25 round shot from a Tokarev got 5" of penetration.
The 5.7x28 SS192 (hollow point ) got about 3 3/4" of penetration.
Where the Tokarev bullet went straight for the 5" of penetration, the 5.7 round went straight for only 1 1/2" then traveled in a 40 degree angle for the 3 3/4" of travel with 3 3/8" penetration.
One bullet traveled in an upwards direction where another traveled downward.
Bullets traveled about 1 1/2 to 1 7/8" higher or lower than the inttal entry point.
Another 5.7 round entered at the top of the wood where it was cut out on a 45 degree angle. It went through about 3/8 to 1/2" of wood then went 5" till it hit the next 3/8" point of wood where the bulllet tumbled and entered with its nose straight up.
For a comparson, I shot a AR15 with a 16" barrel at the same wood target set up and at the same distance of 25 feet and the AR shot through 13" and zipped out the back so I'm not sure how deep the AR would have penetrated.
I added 22lr, 45acp and 9mm to Five-Seven vs. Tokarev Penetration Test using the same boards and same distance. The 45acp FMJ from a HK USPc got 2 1/8" of penetration. The 9mm FMJ from a HK P-7 got 3 1/2" of penetration and the 22lr from a Colt 6" revolver got 3/4" of penetration. The .22's were hollow points and I need to reshoot this with .22 solids to more closely match the other calibers results.

To recap here are the penetration depths.

7.62x25 ---5"
9mm ------ 3 1/2"
7.5x28 ----3 3/8"
45acp ----- 2 1/8"
.22lr ------ 3/4"
.223 -------13"+

All rounds traveled in a straight line into the wood except the FN 5.7 which tumbled. The 5.7 rounds started to tumble at about 1 3/4" in depth. The 5.7 rounds impacted near a knot in the wood and only tumbled to a depth of 2 1/2" due to the hard wood in the knot area.

December 8, 2004, 02:43 AM
Thanks for the link Mr. Roberts. That was exactly what I was thinking of so it saved a lot of trouble. His earlier tests with room sized walls are pretty interesting too. I don't think I would have tryed that because of the costs. I might try catching some bullets in wet pack after they go through some walls, but his BOT has answered most of my questions.

Not very related, but here is a picture from the thread showing rifling marks from a rifle bullet skimming a board. I just like the pic.

December 8, 2004, 08:13 AM
The real problem is they don't build houses like they used to. :( JT

December 8, 2004, 08:33 AM
probably the same rounds the skymarshalls use would be your best bet, Glaser safety slugs.

m60a3, what's your source for that? Everything I've read indicates that the FAMS is using 357 SIG JHPs.

December 8, 2004, 12:49 PM
It takes two layers of drywall to stop a shotgun WAD; the little plastic thingy in the shell. Fiberglass insulation between the walls make no difference.

Brick and cinderblock will stop just about any single rifle or pistol round.

Concrete kicks butt.

I used to use pressure treated 4x4's to stop .22LR from a pistol. It never went more than halfway through.

December 8, 2004, 12:51 PM
Air marshalls are NOT using Glasers or any other type of frangible ammo.
.357 Sig JHP

December 8, 2004, 02:10 PM
Several decades ago, it was common for the ammuniton companies to list the penetration of various handgun loads, usually in 1" pine boards spaced 1" apart. IIRC the .357 Mag, .30 Mauser, and a few other rounds made it through 10 or 11 boards. Note that sheetrock is flimsy by comparison.

Hatcher's Notebook has photos of .30/06 ball rifle penetration . . . up close, it went through about a foot of oak. Further away - after the bullet had stabilized - it went through over 30" of oak. (That's right, over thirty inches.)

Bottom line - ordinary frame housing materials will not stop any conventional round that has serious value for self defense. (Let's not get into bean bags and tasers . . .)

December 8, 2004, 03:26 PM
When I was a Deputy this subject came up quite often, enough power to stop an intruder, with the least over penetration. The accepted recommendation was a 12 ga pump shotgun, loaded with #4 Duck & Pheasant shells. At close range (10 ft) this combination is stunning in its devastation, yet it sheds energy very quickly when going through walls, this birdshot load probably has the least chance of exiting a home and threatening someone next door. Buckshot, while delivering a devastating short range blow, will over penetrate, will go through several walls and easily exit a home, and be dangerous to innocent bystanders.

The reasoning behind the pump shotgun is pretty simple, the sound of a pump shotguns action is very distinct, and I know of a case where hearing that sound has made a home invader make a hasty exit.

Jim K
December 8, 2004, 06:00 PM
It is a common gunzine myth that this or that round is ideal for home defense because it won't over penetrate. Most of that is nonsense, put out by people who have never tried any of the rounds they tout so highly.

Even shotguns with No 7 shot will blow a hole in two layers of dry wall and have enough smoke left to seriously injure someone on the other side. It is simply nonsense that there is a home defense gun or ammunition that will kill/disable an intruder and yet be harmless to others inside the house.

Another myth is that a shotgun will "fill a room with shot so you can't miss", a silly idea most recently seen repeated in Gun Tests. In reality, a shotgun load spreads about 1 inch per yard, so across an average room the spread will be about 3-4 inches. Not only is this not "filling a room with shot", it indicates that the shotgun had better be aimed rather than just pointed somewhere in the direction of the target.


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