Forget the moving the target, put a bear silouette up at 10 paces and shoot a load of 00 at it. If your pattern opens up, then you're hoping one of those pellets lands in a fatal spot, remember you only have 15 of them. Also if you look at the terminal power of a single 00 pellet, it's not a hole lot more than a 32 pistol, which I would never in a million years consider suitable against a bear.
So, if you can't trust your life to one 00 pellet, and I sure wouldn't, that means you need a pattern tight enough for the pellets to land in a single mass, which means aiming is just as critical as for a single projectile.
So you're back to slugs, which means you're trying to make a bird gun into a powerful handgun, more or less.
