I usually seat the bullet for what it calls for from the book or bullet makers website, then I start low on charge and work up till I get good groups but what if my es is high say 30 fps it would mean my load is not good cause the high es. So Cortina says to start with seating depth 20 thousands shorter than what your bullet jams into lands, for 223 that would put me at 2.290, work up charge till you get low es and don't worry about group till you get that, once you do then go down on seating depth till groups are good and pretty much your done, besides getting at least 2 good and seating accordingly. Well the bullet manufacturer is saying to seat at 2.225 so it will take a lot of shots to get there from 2.290 if it does shoot better at 2.225 so now let's say I have a good powder charge and my bullet shoots best at 2.225, well the pressure is going to increase and is my es still gonna be good like when I started at 2.290 to find that charge. I will also say that I'm getting good groups at 2.225 and I tried making it longer and the groups fell off more the longer I made it, I went to 2.250 and stopped there cause it kept getting worse. Because of the cold and lots of snow here I haven't been using the Chrono so my groups are good at 100 and hopefully my spreads are low, if not, then what, change powder, primer? But my main question is why not seat or at least start where manufacturer recommends and if my final seating is very far from where I worked up charge will the charge stay the same, I don't think it would.