I have found that a good place to start is to use Federal Gold Medal hulls, Remington Primers, CB 1100-12 wads and PB powder and 1 oz of lead shot. Winchester Primers and PB powder don't work well in the cold weather we have in Minnesota. Velocities of 1100 fps can be achieved at less that 6000 psi. An even lower
pressure can be achieved by using Federal Top Gun empties since they have a card board base.
Mike