lyman #6 has the data for 3 1/2" hevi-shot. 1 3/8oz 1 1/2oz 1 5/8oz. Here is one load: federal 3 1/2" plastic case,fed 209A, 35gr steel, one BP TPS 3 1/2" wad, one 1/4" 20ga under shot felt,one mylar wrap inside wad,1 5/8oz hevi-shot, 21gr BP#47 buffer, one 16ga over shot card, fold crimp, 1320fps, 12900psi. A very painful load to shoot i bet. with T sized pellets you might not be able to use the 1/4" felt