Using 3" shells won't really give you any additional lethality over 2.75" rounds at typical HD distances.12GA Remington Pump with 3" shells of No. 4 buckshot.
You may be better off just loading all five chambers with .45 LC...I recently read (sorry, I can't remeber where) a rather extensive evaluation of .410 buckshot shells as defensive rounds; they have very limited penetration and are pretty anemic for use against two-legged predators, especially when fired from a short-barreled weapon like the Taurus Judge.I use 000 buck in my Judge. The first 3 shells are 000 buck and the last 2 are 45 longs. That should stop pretty much anyone.