Why will fire formed Neck sized brass show pressure quicker than full length sized brass? The reason I ask is I had some loaded rounds I took the bullets out of and since I size my necks with the LCD I didn't want to remove the primers. I ran those cases through my Wilson F/L bushing die without the decapping stem and didn't push the shoulder back. I shot these in .5 increments and velocities went up 25-35 fps at each step. When I had shot all of those, I took them and just ran them through the LCD and loaded in .5 grn increments again. The first .5 grain step gained 90 fps and next .5 one was 29 fps faster than the first one. If someone can explain this to me I really would like to figure it out. Thanks