Wasp nests can be smaller- as in mud wasps. In that case, I found that rolling the materials between the palms of my hand, to break it down to smaller fibers, like pipe tobacco, and then dribbling them into the barrel to be packed down with your loading jag, works quite well. The cellulose is fire retardant, and creates a great filler that seals the bore to the gases behind it. Just don't be afraid to use more, than less. you can always find more nest material.
Look for the nests in the fall and harvest them in the winter after a couple of good freezes. Hornets' nest, those head sized structures found hanging from tree limbs, usually no more than 6-8 feet off the ground, are safe to harvest in the winter, too, after hornets leave them, and enter nests in the ground for the season.
They build new nests for their Queens every Spring, so don't worry that you will be depriving them of their homes. Unused hornets nest remain until weather and decay knock them to the ground, where they are devoured by grubs, worms and ants, who used the material in their underground nests. Those Ants can wait. They get everybody eventually. :shocked2: :thumbsup: