Not supposed to load more than one of those type shells at a time. On the other hand, I reload 12 and 20 and have devised an effective #2 buckshot or slug round that is 2” long and works in both pumps and semis, allow the typical Mossberg pump to hold an extra shell in the mag.
I’d be hesitant to use a “homemade” round for home defense. Even using conventional reloads is District Attorney bait in the event that you actually have to defend yourself. 00 or #4 are both good bets. Federal markets a reduced recoil 00 buck load in their “Ranger” lineup that is a great option for home defense. Bird shot is a bad choice-penetration is very low. It produces grotesque but shallow wounds that don’t readily incapacitate the target.