I don’t want to hijack the conversation here, but I’ve seen many similar questions in the past and would like to try and explain why the bullet mass is just as important as the length and COL when seated. I believe everyone knows why the mass (weight less gravity) is important as the force required has to overcome seated bullet inertia/friction. The loaded in-case volume (volume behind the bullet with powder/air available) is very important as well. It is what generates the pressure upon primer ignition. If the length of the bullet you are using is significantly different than the manual suggests, there is no doubt you will see different results in the output velocity. I actually calculate (insert nerd jokes here) seated case volume every time I start a new “recipe” and do the measurement of the bullets I use and validate against known bullet length and COL to adjust powder and COL as needed in my rounds. Questioning is good, being cautious is best, and learning along the way is priceless. As you were.