I usually steer clear of the "This is what I stuff down my barrel" discussions but, I too have tried to find something that would make my GB mortar go bang (besides golf balls). Cardboard didn't do it, nor did a bunch of paper. I have been using a slice of white bread and a marshmallow. I kind of patch the marshmallow with the bread. A slice of bread alone isn't quite big enough. The bread lands 25' out, I never have found the marshmallow. Like CW said, ANYTHING constitutes a projectile. You should be loading accordingly (IE W/projo, not "blank"). I use about 200 grains with bread/mallow, not ear splitting, but about as good a boom as I can get. MIKE