Can anyone identify the differences between models of Mossberg shotguns? I have a 500 and 590, and have seen plenty of the 835, but have also seen the 550 and 600, and don't know how they're different. Are any parts interchangeable? And what about the different bolt and semi versions? Is the 9200 still in production? Haven't seen it advertised on their website, but have seen plenty of new ones around. I've also seen something about a Mossberg 200 external magazine fed pump shotgun... I'd love to see one. Anyone know where to find one or find out about it? And does anyone know of an auto shotgun whose buttstock will interchange with the 500?