Why is it that every time someone mentions a rifle for home defense we have to have the conversation about bullet construction and penetration?
Newsflash - anything that will meet the FBI standards for law enforcement ammunition is going to penetrate
multiple interior walls if you miss - this includes pistol rounds and buckshot as well.
Some rifle rounds may present a threat to your neighbors. Some may not. This will depend on bullet construction and intervening barriers. If you are using the latest high speed 40gr varmint grenade and it sails through your floor-to-ceiling window, then it may still pose a risk to neighbors (as will 9mm and buckshot). If you are using a semi-auto .308 with FMJ and pulling the trigger as fast as you can, even a brick-sided home may not contain the rounds.
However, the best way to minimize the "overpenetration" problem is to:
1. Stop the threat in as few shots as possible
2. Hit the threat when you do fire
Rifles lend themselves well to both of those problems and with the right bullet selection can penetrate even less than pistol or buckshot.
For example, this
7.62x39mm Hornady 123gr VMax actually penetrates LESS than the FBI recommended standards for PISTOL ammunition in bare gel. And this
Federal Hi-Shok 123gr softpoint penetrated about the same as many common law enforcement pistol rounds (but with a much bigger wound cavity).
On the flip side,
Wolf 154gr softpoint penetrated the entire gelatin block and another 5" of polyester fiber being used to catch the bullet. It might not be the best choice where neighbors are concerned, even though it is a softpoint 7.62x39.