Projectiles from all firearms, regardless of what style or type, can over penetrated in a house and can potentially travel outside. I have seen the aftermath of a 9mm negligent discharge in someone's house. It went through two walls, a heavily wooded entertainment center, two pillows, a leather couch, a double paned window and a trash can outside. The bullet was never recovered. There is always a risk of over penetration (unless you're shooting bean bags). Everyone has a theory and reasons that justify their decision. This has been a healthy debate and one which all will never agree.