Over the years I've been using 5744 (smokeless) powder, 20 grains. I pack down 1/4 piece of tissue paper over powder with a pencil eraser end (no metal). that keeps powder over primer. then I use a .462 dia. lead bullet, about 480 grain. Since most trapdoors have been over shot, the .458 dia bullet may be sloppy so I increased it to .462 dia. No failures to date.