I just used data from my previous loadings of 170 grain bullets and worked up. My Marlin has always liked W748 and sure enough it a winner with the 160 FTX's at 35.5 grains with a CCI200 primer. I did try IMR 3031 but the accuracy was not there in my gun. Worked the 3031 up to 31.5 grains with no pressure signs.