I am trying to determine velocity based on a specific load. I am shooting 155gr lead cast bullets using Hodgdon Clays. I cant find any data on the bullets and have read to use jacketed data minus 10% to start. I was trying to calculate the average FPS based on the difference in valocity betwen the minimum and maximum recomended loads on Hodgdons website for a 155gr Hornady XTP. With a minimum load of 7.7gr of HS-6 the velocity is 1035 and with a max of 8.5gr the FPS is 1137. That is a difference of 102fps. The difference between 7.7 and 8.5 is .8. If you devide 102 by 8 you get 12.75. So I was assuming that for every tenth of a grain, there is roughly a 12.75fps increase or decrease depending on which way you go. Can I assume that or is that just nuts??