Buckshot vs. birdshot for home defense - does it matter?

It matters a lot. Birdshot is for birds — at defensive distances it tends to under-penetrate and may not reliably reach vitals, especially through heavy clothing or a barrier. For home defense run 00 buck or #1 buck; both deliver multiple pellets with FBI-spec penetration. The one step everyone skips: pattern your specific gun with your chosen load at your actual hallway distance (often 5–7 yards). Loads pattern differently in every barrel, and you need to know your spread so every pellet is accounted for.