If your cases are basically full and you are still experiencing ignition problems, Pierre van der Walt recommends that you place 2 grains of Unique on top of the primer with cases that hold up to 130 grains of water, and 3 grains of Unique (or Hodgdon Universal) for cases above 130 grains of water capacity. the .505 Magnum Gibbs holds about 178 grains of water. Mr. van der Walt emphatically stated that no ball powders are to be used as an ignition supplement; flake only for this procedure. A Lee dipper would be handy for this procedure. He also stated that you start with the minimum loads and work up when doing this. This is one hell of a book and I recommend it to all who shoot, hand load for, or own large bore dangerous game cartridges.