I'm in the middle of changing from International Clays to Alliant e3 and want to maintain the same 1200 or so fps. International Clays published recipe calls out about 20.5 grains (#31 bushing). Alliant e3 published calls out 17.4. The MEC bushing for International is a 31, the e3 calls out a 28. The 28 only get me 15 grains, so I work up from 28 and I finally get to 32 to find out it provides me the 17.4 I'm looking for. I can't seem to understand why the recipe or the chart doesn't match. If anyone has an explanation, I love to hear it.