Going for that one almighty supper accurate load then yes. Basically what is going on is every time you resize the case it stretches, thus why you need to trim it. Well to stretch a piece of metal requires it to get thinner. So upon resizing, the die resizes the outside of the case thus making the case wall just a bit thinner. Depending on the factory case, brand, how many times it has been reloaded, how much force the die puts on the case, effect how much you need to trim and the inside diameter of the case that is left. Thus a new case and say a case that has been loaded lets say 10 times, the x10 case will have a different pressure curve then the new case before it can over come the neck tension to start moving the bullet because of the bigger area inside the case. At this level of loading there are a lot more variables, bullet length ogive to base, bullet weight, powder used, primer compound, humidity, barometric pressure and so on. I have shot with guys years ago that had 1,000+ yd loads just for different humidity levels and temps. They would go through a box of 500 bullets and only 10-20 would pass to be loaded.