You just said you're going to use the bird shot to slow them down. You said you only have one round of bird shot. So if you're going to fire multiple times then why even load one round of bird shot followed by 00? That's pointless. Like you said, the idea is to stop the threat. If bird shot is only going to maybe slow a threat, why even waste the space in the gun with it? What if you miss with other rounds? The spread of a shot gun isn't going to be all that much inside a home, chances are you will not hit two intruders with one round. If you try to with bird shot, they might only get a couple of pellets, like you had shot them with a bb gun, and they had better be standing shoulder to shoulder.