All charges of Triple Seven or Pyrodex should be measured by VOLUME not weight. A simple, adjustable blackpowder measure is the correct tool for this job. All loads listed in this brochure are measured by VOLUME.
Triple Seven is a high energy product designed to provide the muzzleloading hunter with higher velocities when used in the same VOLUME as blackpowder. To duplicate a blackpowder load velocity using Triple Seven, you must decrease the powder charge by 15%.
*See WARNING below.http://www.goexpowder.com/images/LoadCharts/Cartridge-Pistol-Revolvers.pdf
38 Spl Black Powder charge ... 16gr FFFg
So download the Triple Seven according to Hodgdon's product description