Originally Posted by shurshot
I'm concerned about family in the next room, neighbors, liability, etc., not "Internet tests".
Where I live, the "next room" would be two pieces of 5/8" drywall (powdered gypsum backed by paper) and if you are lucky, maybe some fiberglass insulation blown in between the sheets. Something that won't penetrate that barrier is extremely weak. Now presumably the reason you are using a firearm in the house to begin with is that there is a threat that is even more dangerous than you shooting a firearm in your house. So if you have that kind of threat, it would seem that stopping that threat promptly is of high importance.
My "evidence" comes from the field, not the internet...LOL! I have hunted and trapped my entire life and have seen what birdshot can do at close range (under 7 yards) out of a 12 Ga shotgun, so I'll stick with my birdshot.
Hunted a lot of 200lb mammals with birdshot during that time?
Turn off your laptops this weekend, go out to a gravel pit, and SHOOT a load of birdshot at 4 or 5 yards (avg. living room distance might be closer to 3 yards), into a gallon jug filled with water. Test #6 birdshot out of a 12 Ga at close range. No, its not a slug or buckshot load, but it WILL leave a big, NASTY rat hole. You may just change your mind about what you read on the "net" from some Mall Ninja, or at least question as to if the person posting spends more time online than on the range.
"Penetration in rows of water-filled, 2-quart (1.89 liter) cartons is approximately 1.5 times that which would occur in 10% 4 degrees C gelatin. Since a U.S. 2-qt. carton is 3.75 inches (9.525 cm) wide and 3.75/1.5 = 2.5, one simply multiples the number of the carton in the row from which a test bullet was recovered by 2.5 to determine approximate gelatin penetration in inches or by 6.35 for the reading in centimeter. For example, a shot recovered from carton #6 would correspond to a gelatin penetration depth of approximately 15 inches (38.1 cm). (Cotey, Gus Jr.:"Number 1 Buckshot, the Number 1 Choice." Wound Ballistics Review, 2(4): p. 11; 1996.)
So using this formula, we find that your results are very close to ballistic gelatin results. You got penetration of about 5" at close range. #6 birdshot at 10' from a 12ga typically penetrates about 5-6" with most of the shot at 3-5" in bare gelatin (i.e. no bones, no jacket, no drywall, no skin, no clothing). So using 12ga #6, you have a load that is effective under the following conditions:
1. You attacker is not behind ANY kind of cover. Not even a couch, appliance or drywall.
2. Your attacker is 12' or closer.
3. Your attacker is lightly clothed, or even better, naked.
4. Your attacker is the same size or smaller as the average male (about 19" shoulder to shoulder and about 9" front to back)
5. Your attacker is facing you with his hands out to the sides providing an unobstructed center mass shot.
If any of those conditions change, 12ga #6 birdshot loses a lot of effectiveness. You've made a choice to limit the potential liability by limiting the effectiveness of the firearm to a fairly narrow range so you don't have to worry as much about shoot or don't shoot decisions in a high-stress scenario. That is certainly one way to approach the problem. However, I would submit that making the firearm more effective, getting training, and utilizing a little prior planning to identify safe backgrounds and no-shoot backgrounds gives you more options and ultimately makes your family safer by being more likely to stop the threat that made you decide that firing a gun inside the house was less dangerous than not firing to begin with.