the delta not the total, comparing fast to slow powders. 20 grains of fast powder versus 30 of slow for e.g. the difference is 10 grains out of 437.5. that's 2.2%. a charge 97.8% of another squared in the equation is only a 4.45% reduction in calculated energy. in a 20ftlb recoil 12 ga load that's .87ftlbs. anybody that can feel .87ftlbs of recoil is spending way too much time thinking about it. even at that the weight of the total powder charge compared to the shot payload is still not of much consequence.