With .690" in the 12ga. I assume you will have to use a wad, I use a .715" rd. ball and I cut off the petals of a trap load wad, and use the same data as I would in the trap load, ie: 19grs. of Red Dot, For Black Powder reloads I use the same ball and case although I prefer paper cases, 90grs. FFG, and make up the diff. in space with a card wad and felt wads, followed by a roll crimp. Both loads go about 1200fps. The best advice i can give is to use felt wads in your BP loads that have been soaked in BP lubricant as this eases the cleaning chore by a mile. If your over powder card wad is a good fit it will prevent powder contamination, enjoy.