You can simply use the Lyman data for their solid base wadcutter and be on your way. Two full power (but not +P) loads that I use with the bullet you've shown are 3.5 grains of Bullseye or 4.0 grains of 231/HP38. That gives about 775-800 in a 4" barrel .38 Special and works beautifully on critters and targets without being abusive to guns and shooters. When you seat the bullet, seat them with the casting sprue mark forward so you use the best end of the bullet for the base.