I went ahead and did the shells quickly in about an hour or so this morning, since I basically had a system in place already in another game, it wasn't hard to do.
Let it rain shells :)
They are SceneryObjects that when they hit the ground I bounce them randomly one time then draw it into the display taking it out of a movement array.
The way that bullets, pellets, and now shells are handled is that they cycle through 150 pre-made projectiles, so only 450 total projectiles ever exist.
Next up is sound, then it'll basically be ready. I've been working on a couple scores I'd like to use.