Jack,
Here's an old trick. If you slowly pour the long grained powders onto the side of the funnel, rather high up near the top, you can get the powder to swirl around the funnel a time or two as it descends toward the case mouth. It won't bridge or "sit over the case mouth", it will enter the case without problems. Additionally, you'll get far more even powder density within the cases than you will with random tapping- this is how the operators of pressure guns load powder into the cases that are prepared for testing purposes.
Bob