They didn’t teach you not to flag your barrel at the corners? Or you were using an M16 instead of an M4?

And at 10 meters you’re going to get about a 5 inch spread on that birdshot. At 3 meters (a standard 10x10 foot room) you’re looking at about 1.5 inch spread. At 1.5 inches it’s absolutely going to say hello to the next room over. Granted, an honest to god slug is going to go through the next 5 rooms at least.

Pistols are nice but actually require more training because people hold them wrong, sight them wrong, and reset them wrong, whereas a rifle or shotgun is a lot more intuitive as long as your target is reasonably close.

The conclusion is obvious. The best home defense weapon is a claymore mine rigged to your front and back doors with a poorly executed wire that taps a battery. Hopefully it only does it when the door opens. No worries about neighbors or missing the bad guy.

Source - Combat Infantry Badge, circa 2003 and way too much time being told I couldn’t do things I thought were perfectly reasonable.