Animation: Toxic kittens animations are a good choice. Close to my favourite shotgun animations. definately one of the best so good choice using those. Feels like your really pumping the gun.

Model: mossbergs are a basic sort of shotgun and this is a good job of recreating the firearm. Although the muzzle right near the end does look a little thin. The only thing that i have againts the model really is that it doesnt have a pistol grip. No points lost though, but it does effect the world model with the floating grip syndrome that weapons without pistol grips in the m3 slot get. But I'ts not too noticable. It's good that you offered the option of with or without shell holder.

Texture: Nice and simple, no overdone normal or phong maps. I think this skin is well made and straight to the point.