I shoot clays using 7.5 shot. Was at the range the other day and happened to see this 55 gallon drum hiding in ambush. Well, I had to get it before it got me so I unloaded a barrel on her from about 15 yards away. After the smoke cleared, I noticed a large hole, about 3 or 4 inches in diameter in her midsection with a few lose pellet indents around it. I say it was DOA, no exit wound was found on the other side.
For home defense I would say that 7.5 or 8 shot would be perfect to stop a bad guy in his tracks. 15 yards is 45 feet, if you have a straight shot into a room and its over 45 feet, you have a really nice house with big rooms!
Bob