Bring a large pot of salted water to a boil. Add your manicotti shells to the boiling water and cook for about 4-6 minutes until they are partially cooked.
Preheat your smoker to 275 degrees Fahrenheit.
While the noodles cook, combine the ground Italian sausage, cream cheese, BBQ Rub and mozzarella in a medium bowl. Mix until combined.
Remove the partially cooked noodles from the water to a cooling rack set on top of a baking sheet lined with foil. Stuff each shell with a portion of the sausage mixture. Grab a couple of ounces of the sausage and roll it into a cylinder shape before sliding it inside the pasta shell. Press with your fingers to load the shells with the sausage mixture.
Wrap each stuffed shell with a slice of bacon, tucking the ends under the stuffed shells to prevent the bacon from unraveling while they cook. Set the wrapped shells back on the cooling rack.
Place the pan of shotgun shells on the smoker and close the lid. Smoke for about 1 1/2 hours, or until the internal temperature of the sausage reads 170-175 degrees Fahrenheit and the bacon has rendered. Remove the pan of shotgun shells from the smoker.
In a small bowl, combine butter, garlic powder, Italian seasoning, and Parmesan cheese. Baste liberally across the tops of your finished shotgun shells. Allow the finished product to cool for 5 minutes or so before transferring it to your serving platter.