There is nothing special you need to do when loading compressed loads. You may need to use a drop tube or tap the case to get the powder to fit - seating the bullet will then actually compress the powder. It is possible that compressed loads stored for long periods of time, or in varying temperatures, may actually move the bullet. Generally, the most accurate loads are those that fill the case near 100% capacity. There is no real correlation between velocity spread and accuracy. Obviously, you don't want huge variations, but the most consistent velocity load may not give you your best groups.
