The problem with that logic is not the number of projectiles, nor the total weight of the shot load and velocity that matters most, but the mass of the individual projectiles that matters. The smaller ones do not carry enough retained energy to penetrate. Think of it this way. Would you rather I hit you with a fistful of thrown gravel or a fistful of rocks?
No doubt that would ruin a perp's day. If he was wearing a T-shirt. It the dipstick in your home was a Hell's Angel wearing a leather jacket, you'd probably just piss him off and he'd beat you to death with your shotgun.
The debate over 00-Buck, #1-Buck or #4-Buck for defensive use will rage on forever, I suspect, but I would not even consider anything smaller than #4-Buck, personally, anything less would be subject to too many variables to be considered a reliable stopper, IMO. For me, I'd stick with 00-B or #1-Buck only.
Of course, YMMV. But along the continuum from buckshot down to birdshot, at some point along that line the physics will win out. I don't know if your goose load is that far or not, but virtually no experienced defensive shotgun instructor I've seen recommends anything below #4-buck for that reason.
Please note, it certainly CAN be effective. Depending on distance, perp's clothing and physique, shot placement, etcetera, I'm not saying it's an inconsequential load. I don't think one can argue it's a definitive stopper though. When you have to put a perp down, you need to put him DOWN. Every time.
